6MW and Gait Speed PD

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Research ReportTest-Retest Reliability and MinimalDetectable Change on Balance andAm bulation Tests the 36-Item Short-Form Health Survey and the UnifiedParkinson Disease Rating Scale inPeople W ith ParkinsonismTeresa Steffen, Megan Seney

B a c k g r o u n d a n d P u r p o s e . Distinguish ing be tw ee n a clinically significantchange and change due to measurement error can be difficult . The purpose of thisstudy was to determine test-retest reliability arid minimal detectable change for theBerg Balance Scale (BBS), forward and backwa rd functional rea ch , th e R omberg Testand the Sharpened Romberg Test (SRT) with eyes open and closed, the Activities-specific Balance Confidence (ABC) Scale, the Six-Minute Walk Test (6MWT), com-fortable and fast gait sp ee d, th e Timed Up & G o Test (TUG), th e Medical Outcom esStudy 36-Item Short-Form Health Survey (SF-36), and the Unified Parkinson DiseaseRating Scale (UPDRS) in people with parkinsonism.S u b j e c t s . Thirty-seyen community-dwelling adults with par kinsonism (mea nage =71 years) pa rticipated. The Ho ehn and Yahr Scale median score of2wa s on t helower end of the scale; ho wever, th e sco res ranged from 1 to 4.M e t h o d s subjects were tested twice by the same raters, with 1 week be tweentests. Test-retest reliability was calculated using intraclass correlation coefficients(ICCs). Minimal detec table ch ange was calculated using a 95% confidence interval(MDC95).R esul t s . The ICCs for test-retest reliability we re abo ve .90 for th e BBS, ABC Scale,SRTw ith eyes c losed, 6MWT, and comfortable and fast gait sp ee ds. TheMDC9 valuesfor those functional tests were: BBS = 5/56, ABC Scale=13%, SRT with e yesc losed=19 seconds, 6 M W T = 8 2 m, comfortable gait speed=0.18 m/s, and fast gaitspeed=0.25 m/s. The ICCs for test-retest reliability of SF-36 scores were above .80,with th e exc ep tion of the social functioning subsca le. The MDCc,, values for th e SF-36ranged be twe en 19% and 45%. The MDCg, values for the UPDRS Activities of DailyLiving section. Motor Examination section, and total scores were 4/52, 11/108, and13/176, respectively.D i s c u s s i o n a n d C o n c l u s i o n . Minimal detec table ch ange values are useful totherapists in rehabilita tion and weliness programs in determining whether changeduring or after intervention is clinically significant. High test-retest reliability of scoresfor th e BBS, ABC Scale, SRT with eyes close d, 6MWT, and gait sp eed make the mtrustworthy functional assessments in people with parkinsonism. The SF-36 andUPDRS provide quality-of-life and disease severity rating values in the ongoing assess-ment of peo ple with pa rkinsonism.

T Steffen, PT, PhD, is Professor,Program in Physical Therapy, Con -cordia University Wisconsin, Me-quon, W is. Dr Steffen s m aiiingaddress is: N102 W7525 St JamesCt, Cedarburg, Wl 53102 (USA).Address all correspondence to DrSteffenat: [email protected] Seney is a stud ent in the Pro-gram in Physical Therapy, Conc or-dia University Wisconsin.[Steffen T, Seney M. Test-retest re-liability and minimal detectablechange on balance and ambula-,tion tests, the 36-Item Short-FormHealth Survey, and the UnifiedParkinson Disease Rating Scale inpeople with parkinsonism.Phys her 2008;88:733-746.] 2008 American Physical TherapyAssociation

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Functional Assessment in ParkinsonismP hysical therapists strive to cre-ate interventions that focus onimproving a patient's functionalability. Function gained during or af-ter therapy often is measured bychange in scores on a functional as-sessment instrument over time.*When results improve from one as-sessment to another, therapists of-ten assume that the patient has pro-gressed. Unfortunately, there is achance the difference between as-sessments is a result of measure-ment error. 2 A comm on probleminvolves deciding whether the re-sults are clinically significant or anerror in measurement. To determinew^hether an improvement is signifi-cant, researchers need to provideminimal detectable change (MDC)scores, by patient population, fortests.Minimat detectable changeisdefined as the minimal amount ofchange that is not due to variation inmeasurement.-^Clinicians can interpret MDC scoresas the m inimal change that is not dueto error. Scores at or above the MDClevel are due to patient improvementon the test rather than measurementerror. Measurement error includesexpected or typical variability in pa-tient performance. In the literature,various methods are utilized to cal-culate change scores, including thestandard error of measurement(SEM), minimal clinically importantdifference (MCID), and smallest de-tecta ble difference (SDD). The SEMis calculated by multiplying the stan-dard deviation by V l rninus the re-liability coefficient, which is the sta-bility or variability of response andindicates the range of the scores thatcan be expected upon retesting.'*The MCID is the smallest meaningfulchange, as judged by the patient orexperts in the field,' and is deter-mined by questioning or observingthe patient. Some researchers referto the MDC utilizing a 95 confi-den ce interval (MDC95) as the SDD.?

Once the MDC is determined on aparticular test foragiven population,therapists can interpret whether thechange score for their patient is at orabove the minimal level of detect-able change reported in the litera-ture.Ifthepatien t's score is less thanth eMDCvalue, it is considered to beindistinguishable from measurementerror. Accordingly, a patient whodemonstrates less than the MDCvalue is viewed as not benefitingfrom the intervention. For example,following hip fracture, the MDC is0.08 m/s for comfortable gait speed.''If a patient's comfortable gait speedincreases less than 0.08 m/s, thechange is within m easurement error,leading to the conclusion that a clin-ically significant change did not oc-cur as a result of the therapeuticintervention.To evaluate MDC, researchers firstmust measure test-retest reliability.On functional tests, a7 day separa-tion period typically is used. Sourcesof error may include inconsistenciescaused by the participant's physicalor mental condition, variations in thetesting procedure, or tester error.Maintaining consistency and usingstandardized protocols for testing,such as using the same tester, setu p,testing order, and time of day, canimprove test-retest reliability.The MDC is based on theSEMand iscalculated using the following for-mula':MDC = of confidence XXThe 2r-score represents the confi-dence interval from a normal distri-bution, SD is the standard deviationat baseline, and r is the test-retestreliability coefficient. The multiplierof \ 2 is used to account for theadditional uncertainty introduced byusing difference scores from mea-surements at 2 points in time. Someresearchers*' suggest using a confi-

dence interval of 90 due to its usebeing more common in the litera-ture; however, a cotifidence intervalof 95 increases the precision ofscore estimation and is the SDD.'Internal consistency, determinedby the Cronbach alpha, ofamultiple-item test such as the Berg BalanceScale (BBS), the Activities-specificBalance Confidence (ABC) Scale, theMedical Outcomes Study 36-ItemShort-Form Health Survey (SF-36),and the Unified Parkinson DiseaseRating Scale (UPDRS) sometimes re-places r or intraclass correlationcoefficients (ICCs) in the MDC for-mula when test-retest reliability isnot reported. Internal consistency isthe extent to which multiple itemswithin a scale or subscale measureone characteristic and nothing else.Internal consistency of a multiple-item test is considered high if it ap-proaches a Cronbach alpha of .90in a given population. Test-retestscores are considered a more con-servative approach when calculatingMDC values' in situations whereboth iqternal consistency and test-retest reliability are reported. Test-retest reliability and internal consis-tency reliability are necessary formsof reliability that should be reportedin multiple-item tests in which itemscores are summed or averaged.One patient population for whichMDC scores would be useful in help-ing to distinguish actual change frommeasurement error is people withparkinsonism. Parkinsonism is a con-stellation of symptoms, includingtremor, rigidity, bradykinesia (slowmovements), and loss of postural re-fiexes. Although Parkinson disease(PD) is the most frequent cause ofparkinsonism, it includes other diag-noses such as Parkinson-plus syn-dromes of progressive supranuclearpalsy and corticobasal degenera-tion. Parkinsonism symptoms createfunctional limitations of balancewhich often are measured in theclinic with the BBS, BCScale, Fun


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Fun ctiona l ssessment in Parkinson ismtional Reach Test (FRT), RombergTest (RT), and Sharpened RombergTest (SRT)and difficulties in mobil-itywhich often are measured withthe Six-Minute Walk Test (6MWT),Timed "Up & Go" Test (TUG), andgait speed. The disease also affectsquality of life (measured most oftenwith the SF-36), Disease severity ismeasured in people with PD withthe UPDRS,Literature Review ofMDC ValuesExtensive literature searches weredone to find all previous test-retestarticles published up to March 2007on each of the instruments listedabove. This was done to determinewhether MDCs could be calculatedfor each of the instruments. Whentest-retest ICCs or Pearson f) valuesand standard deviations were re-ported in the literature, those valueswere used to calculate MDC95 forthat study,BBSTheBBSis a l4-item test, using ordi-nal scoring from 0 to 4 for eac h item,designed to measure static and dy-namic standing balance. The totalscore range is 0 to 56, with higherscores indicating better balance. Theinternal consistency of the BBS ismoderate to high, ranging from ,85to ,98,7-12 In 3 stu dies,^ ^.'^ICCsfortest-retest reliability of ,97 to ,99were reported in subjects withstroke and traumatic brain injury(TBI), respectively. One study per-formed over 1 week on 26 peoplewith PD reported an ICC of ,87,"Four studies contained sufficientdata to determine MDC95, TheMDCc,5 values were 2 for 26 peoplewith PD,'5 5 for 24 elderly peoplewith or without stroke,^ 3 for 20people with hemiparesis,' and 4 for5 people with TBI,''' All of thesestudies were performed 7 days apart.The high test-retest reliability, mod-erate to high internal consistency,and lowMDC95scores in these stud-

ies indicate theBBSisavaluable mea-sure to monitor responsiveness tochange in patients with neurologicaldisease,FRTThe FRT is a static balance test de-signed to measure margins of stabil-ity. Based on a review of 10 articles,test-retest reliability for functionalreach has been shown to vary fromlow to high, with ICCs ranging from,42 to ,93, Nine studies'5-23 exam-ined forward functional reach, and 1study'5 examined backward func-tional reach, with the time betweentests varying greatly from 1 day to 1month , 15-23 Only 3 studies examin-ing test-retest reliability ha d a samplesize over 30,i6'724 Three stud-iesi5,2o,22 reported test-retest reliabil-ity in subjects withPD,One study of26 subjects with idiopathic PD re-ported anICCof,74for theFRTwitha testing interval of 1we ek,' ' and astudy of 14 subjects with PD re-ported anICCof,84for th eFRTwitha testing interval of1day,20Anotherstudy of 10 elderly subjects with noknown neurological impairment and20 subjects with PD, using a testinginterval of a week, reported ICC(2,1) values of ,62 for the subjectswith no known neurological impair-ment, ,93 for subjects with PD whohad a history of falls, and ,42 forsubjects with PD with no history of

Of the current studies examiningtest-retest reliability of the FRT, 4studies'21-23 provided enough datato calculate MDC95, which rangedfrom 4 to 11 cm. Two studies report-ing test-retest reliability ofthe FRTin20 people with PD, with tests 1week apart, demonstrated MDC95values of 4 cm for people who hadfallen, 8 cm for people w ho had notfallen, and 12 cm for 26 people witha diagnosis of idiopathic PD,'5,22Studies on forward functional reachhave provided a wide range ofMDC95 values for people with PD,

and no MDC95 data on backwardfunctional reach,RT and SRTThe RT and SRT are tests of staticbalance that measure the ability tomaintain balance or equilibrium witha narrowed base of support. Cur-rently, there are no studies that haveexamined test-retest reliability of theRT or SRT for subjects with PD, Inone study of 30 subjects with unilat-eral vestibular loss, aged 29 to 78years, test-retest reliability valuesaCC [2,2]) we re,63for theSRTwitheyes open and ,76 for the SRT witheyes closed,25 in a study of 20 sub-jects with central neurological dys-function, aged 58 to 85 years, test-retest reliability values (ICC [2,2])we re ,75 for theSRTwith eyes openand ,97 for the SRT with eyesclosed,25 In 2 studies, one with 18volunteers aged 24 to 39 years'^ andone with 45 volunteers aged 55 to 75years,26 test-retest reliability valuesaC C[2,1] 17andr26 were,72and ,76for theSRTwith eyes closed and ,90for the SRT with eyes open. Onestudy with a small sample size(n=12 used the coefficient of varia-tion (CV), which indicates an associ-ation between 2 variables, andshowed a high degree of variability,ranging from ,14 to ,86, between thetests on 5 consecutive days,2"7 In 2studies, MDC95 scores for the SRTwith eyes open ranged from 9 to 10seconds,25 andMDC95 scores for theSRT with eyes closed ranged from 3to 9 seconds,2526 Test-retest studies

are needed on the RT and SRT forpopulations with neurological disor-ders, including people with PD, BC ScaleTheABCScale is a l6-item question-naire used to measure balance con-fidence in specific situations, withscores ranging from 0% to 100%,Intemal consistency of the ABCScale in 4 studiesi 28-30 ranged from,80 to ,98, These 4 studies also ad-dressed test-retest reliability of the


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Functional Assessment in ParkinsonismABC Scale. The time between test-ing dates ranged from 1 to 4 weeksin various populations, includingpersonal care Home residents, pa-tients from outpatient clinics, andcommunity-dwelling older adults.The test-retest reliability values (ICC[1,1],'9 ICC,28 ICC[2,1],29 and r^o)were .70 to .92.is-28-3o Two of the 4studies28.29 had sample sizes greaterthan 30 subjects, and 3 studies'^^ywprovided enough data to calculateMDCc,5 scores of 18% to 38%. Inthese studies,'9.29.30 MDC95 valuesalso were calculated using the Cron-bach alpha, with results rangingfrom 6% to 15%.Minimal detectablechange values by patient diagnoses,including PD, are needed for theABC Scale.6 M W TThe 6MWT tests end urance by mea-suring the maximum distance that aperson can walk in 6 minutes. Forsome patie nts, it is a submaximal testof aerobic capacity. Eighteen articleswere obtained on the test-retest reli-ability of the 6MWT.si-'


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Functional Assessment n Parkinsonismcomfortable gait speeds2.53,55 and0.24 m/s for fast gait speed.'^Four studies'*^-59 examined test-retest reliability in community-dwelling elderly people. Intraclasscorrelation coefficients ranged from.79 to .95 overall,5


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Fun ctional ssessment in Parkins onismUPDRSThe UPDRS is the gold standard in-strument used to measure disease se-verity in PD. It has 3 subscales:IMentation, Behavior, and Mood(ra ng e= 0- l6 ), IIActivities of DailyLiving (ADL) (range=O-52), andIIIMotor Examination (range=0-108). A total score (range=0-176)can be derived by summating the 3subscales. Lower scores indicate aless involved disease process. TheUPDRS has moderate intemal con-sistency values across multiple stud-ies in the 3 subscales and totalscore. A Cronbach alpha value of.79 has been reported for the Men-tation, Behavior, and Mood sub-scale,** Cronbach alpha values of .85to .92 have been reported for theADL subscale,*^ -**' Cronbach alphavalues of .88 to .95 have been re-ported for the Motor Examinationsubscale,8'''83-85 and a Cronbachalpha value of .96 has been reportedfor the total UPDRS score.s^'One study**^ exam ined the test-retestreliability of UPDRS scores in 400patients with early stage, mild PDwho were not taking medications.The subjects were examined on 2occasions, separated by an averageof 15 days (SD=8). The ICC (1,1)values were .74 for the Mentation,Behavior, and Mood subscale, .85 forthe ADL subscale, .90 for the MotorExamination subscale, and .92 forthe total score. The calculatedMDCgj values were 2, 4, 7, and 9,respectively.^^ In 26 ambulatory sub-jects with idiopathic PD and no co-morbidities, test-retest reliabilitywith a7 day interval between testswas .84 for the Motor Examinationsubscale and .74 for the total s co re .''The MDCs were 13 and 15, respec-tively.'^ Test-retest reliability of Mo-tor Examination subscale scores wasevaluated in 34 patients with ad-vanced PD on 2 separate occasions,1 to3w eeks apart, with an ICC (3,1)of .90.88

Minimal detectable changes of to 2points for the Mentation, Behavior,and Mood subscale, to 4 for theADL subscale, 7 to 8 for the MotorExamination subscale, and 9 for thetotal UPDRS encompass the existingstudies. Different versions of theUPDRS are being used in studies, anda shorter version is being developed.The lower reliability of the Menta-tion, Behavior, and Mood subscalescores suggests the need for cautionwhen using reliability values to cal-culate an MDC value. Physical thera-pists are most interested in the Mo-tor Examination subscale of theUPDRSto measure responsiveness tochange.The purpose of this study was todetermine the MDC95 for peoplewith parkinsonism on the followingtests and measures: BBS, forward andbackward fimctional reach, RT andSRT, ABC Scale, 6MWT, comfortableand fast gait spe eds, TUG, the 8 sub-scales oftheSF-36, andUPDRS(Men-tation, Behavior, and Mood subscale,ADL subscale. Motor Examinationsubscale, and total score).MethodSubjectsParticipants were recruited via bulle-tin adve rtisements and flyer distribu-tion at local fitness centers, physicaltherapy sites, meal sites throughoutsoutheast Wisconsin, Wisconsin PDorganizations, church bulletins, news-papers, and other local news media.Previous research study and probono clinic participants also werecontacted, and advertisements wereplaced on the Concordia UniversityWisconsin Web site and in facultybulletins.Eligibility for the study was deter-mined by the presence of a clinicaldiagnosis of PD or Parkinson-plussyndrome. All potential volunteerswere contacted by telephone andgiven an oral questionnaire. Partici-pants were included if they were

able to stand independently for 1minute and could walk indepen-dently with or without the use of anassistive device. Participants wereexcluded if they reported a history ofa heart condition limiting their activ-ity level, experiencedafall as a resultof dizziness or fainting within theprevious 2 months, or required helpwith following directions.A demographic questionnaire (sex,date of birth, date of diagnosis withPD or Parkinson-plus syndrome,ethnicity, living situation, history offalling, other medical conditions,and current medications) was com-pleted on the first day of testing andreviewed in the participant's pres-ence with a researcher to ensure ac-curacy. Participants were remindednot to change medications duringtheir scheduled test week and totake medications at the same time onboth testing days.During the spring of2007,37 partic-ipants with PD (n= 35 ) or Parkinson-plus syndromes (n = 2) met all inclu-sion criteria and consented toparticipate in this study. This samplereflected the general demographicsof the PD population, with moremen (n= 26) than women (n = l l )and an elderly age distribution (m eanage=71 years, SD=12). There was awide range of UPDRS total scores(mean=33/176, nmge=7-70), dem-onstrating a sample that captured awide spectrum of disease severity.The average H&Y score was 2(range=l-4). Distribution of H&Ystages were: 13 subjects in stage 1, 7subjects in stage 2, 9 subjects instage 3, 8 subjects in stage 4, and nosubjects in stage 5.The average disease duration was 14years (SD=6), and participants wereprimarily of white/non-Hispanic de-scent (n=36), with 1 participant ofAsian/Pacific descent. Of the 37 par-ticipants, 32 were living at homewith an other pe rson, 3 were living at


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Functional Assessment in Parkinsonismhome alone, and 2 were in assistedliving facilities. The mean num ber offalls in the previous 6 months was 7(range= 0-182 ); 21 participants hadexperienced more than one fall.None of the participants changedmedications during their testingweek, and all participants reportedtaking medications at the same timeon both testing days. Thirty-one par-ticipants were using levodopa, withan average of 412 mg/d (SD=310,range= 125-1,150). Participants, onaverage, had3comorbidities (SD =2,range=0-6), including 17 with ar-thritis, 3 with asthma, 7 with a his-tory of cancer, 11 with high bloodpressure,5with low blood pressure,1 with diabetes, 8 with a previousfracture, 9 with depression or othermental health condition, 6 with ahistory of heart disease,7with osteo-porosis, 1 with stroke, and 14 withother, unspecified comorbidities.ProcedureTesting was administered atConcordia University Wisconsin. Anyclasses scheduled to occur in thevicinity of the testing area were re-located to limit interruptions, andbarriers were placed to ensure par-ticipant privacy. After signing con-sent forms, testing began with theSF-36 questionnaire and completionof the dem ographic information. Bal-ance testing followed and consistedof 4 tests administered to each par-ticipant in the following order: BBS,forward and backward fimctionalreach, RT and SRT (eyes open andeyes closed), andABCScale. The am-bulation tests and the UPDRS wereadministered last and don e in the fol-lowing order: 6MWT, UPDRS, TUG,and comfortable and fast gait speeds.Each day total testing time per par-ticipant was approximately 1 hour.Prior to testing, all researchers weretrained in their assigned test, andthey performed the same duties oneach testing day. Researchers whocollected the reliability data weremonitored by the coinvestigators be-

fore and during the testing proce-dures to maintain accuracy. Allresearchers had previous patient ex-perience using the functional tests. Ifan assistive device was used, thetype was documented and the par-ticipant was required to use it on th esubsequent testing day. Thirty-nineparticipants were scheduled for thestudy; 2 participants cancelled dueto weather or transportation issues.Researchers did not have access tothe previous test results on the sec-ond day of testing.Test-retest reliability w as establishedover a period of 7 days in all partic-ipants, with the exception of 1par-ticipant, who was tested 10 daysapart. Although a 14-day separationmay be preferred for the SF-36 ques-tionnaire, a 7-day interval was usedbased on previous test-retest studiesof the other functional assessments.Balance testing The method forthe BBS test followed the originaldesign,^ which consists of 14 itemsscored on a scale of to 4.Ascore of0 indicates the participant was un-able to complete the task, and ascore of 4 indicates the participantwas able to complete the task basedon the assigned criteria. The floor-to-seat height of the chair used on items1, 3, 4, and 5 was 47 cm. The heightof the chair without armrests usedon item 5 was 44.5 cm, and theheight of the step stool used on item12 was 23 cm. A 1.27 cm (0.5-in)slipper was used on item 9 The par-ticipants were asked to perform eachoftheitems on th e originalBBS,withrests as needed. The 14 items werescored by a total of 3 researchers.One researcher scored item 8 whilethe participants performed the FRT,another researcher scored items 7and 13 while the participants per-formed the RT and SRT, and 1 re-searcher scored the remaining 11items.

Equipment used for forward andbackward functional reach includeda level with attached w ooden slidersfixed to an adjustable tripod with Crings. Participants were asked tomake a fist, raise their dominant armparallel to the floor with the elbowfully extended, and reach as far for-ward or backward as possible with-out losing their balance, lifting theirfeet off the ground, or touching theequipment. The foot placement andmethod of reach were not con-trolled, except to keep the arm at theheight of the level. Participants whoinquired about foot placement wereinstructed to stand in a comfortableposition. Participants were allowedmultiple p ractice trials until they per-formed the test correctly. Once aparticipant was able to perform thetest correctly, 2 graded trials werecompleted. The dominant arm wasrecorded on th e first testing day andused on the second testing day tomaintain consistency. The averagesof the2trials for each direction wereused for data analysis, due to thehigh intratrial reliability reported inprevious studies.' *** Measurementswere recorded (in centimeters) us-ing the third metacarpal as the refer-ence point. Two researchers partici-pated in the data collection. Oneresearcher gave instructions andmaintained participant safety. Theother researcher adjusted the equip-ment to match the participant's ac-romion height, adjusted the woodenslider during reach, and recorded ini-tial and final m easurements.The RT was performed with feet to-gether and eyes open for 60 secondsand with feet together and eyesclosed for 60 seconds. The SRT wasperformed in a tandem standing po-sition, with the dominant foot be-hind the nondominant foot for 60seconds with eyes open and for 60seconds with eyes closed. Timingstarted after the participant assumedthe proper position and stopped ifthe participant m oved his or her feet


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Functional Assessment in Pari insonismfrom the proper position, touchedthe table, or opened his or her eyeson the eyes-closed trials or when themaximum balance time of 60 sec-onds was reached. Participants w eregiven assistance to assume the testposition and allowed rest breaks ifneeded. Up to 3 trials were per-formed if the maximum balance timewas not reached in either of the first2 trials. Data analysis utilized thelongest balance time of all of the tri-als. Upper-extremity use was notcontrolled during testing. One re-searcher administered the RT andSRTto all participants, while anotherresearcher supervised participantsafety.The ABC Scale was administered asan interview consisting of 16 itemsdescribing various activities forwhich participants are asked to ratetheir confidence in maintaining bal-ance on a scale of0 (not confident)to 100% (completely confident). Fi-nal scores were determined by cal-culating the average score on the 16items. To assist participants, an en-larged version of a 0-100 scale wasprovided.Ambulation All ambulation testswere performed on a level tile floorunder quiet conditions. The 6MWTwas conducted in a 3-m-wide hall-way with a 15-m area marked off at1-m intervals and large cones placedat each end. Participants were readthe following instructions: When Isay 'go,' I want you to walk aroundthis track. Keep walking until I say'stop'or until you are too tired to goany further. If you need to rest, youcan stop until you're ready to goagain. I am interested in measuringhow far you canwalk.You can beginwhen I say 'go.' The following en-couragements were provided: (1) af-ter 1 minute, You are doing well.You have 5 minutes to go. ; (2) at 2minutes, Keep up the good work.You have 4 minutes to go. ; (3) at 4minutes, Keep up the good work.

You have 2 minutes left. ; and (4) at5 minutes, You are doing well. Youhave only 1 minute to go. Fifteenseconds prior to completion, partic-ipants were informed that timewould stop shortly, and the test wasstopped at 6 minutes.ô Total dis-tance walked was measured to thenearest meter.For the TUG, participants were in-structed to sit with their back againsta chair (47 cm from floor to seat w itharmrests), feet behind the tapemarker, and arms resting in their lap.Participants were instructed to inde-pendently rise on the word go,comfortably walk a clearly markeddistance of3m, turn around a cone,walk back to the chair, and sit downwith their back against the chair.Time started once the participant'sback left the chair and ended whenthe participant's back returned tothe chair. Time to complete thecourse was measured to the nearest100th ofasecond. O ne practice trialand 2 timed trials were performed;the 2 timed trials were averaged fordata analysis.For the test of comfortable gaitspeed, participants were asked towalk 10 m and were instructed to walk at your own comfortable walk-ing speed and stop when you reachthe far line. For the tes t of fast gaitspeed, participants walked the 10 mwith the instructions to walk as fastasyou can safelywalk and to stop atthe far line. Time to complete thecentral 6 m was measured to thenearest 100th of a second using astopwatch. Time started when anypart of the foot crossed the plane ofthe first tapeline and ended whenany part of the foot crossed the p laneof the 6-m mark. Rest breaks wereallowed between tests or trials, ifneeded. Participants completed 2comfortable gait speed trials, fol-lowed by 2 fast gait speed trials. The2 trials were averaged for data anal-

ysis,and gait speeds we re calculated(in meters per second).SF 36 The SF-36 was administeredvia personal interview by 2 research-ers using the interview script pro-vided in the SF-36 Health Survey:Manual and Interpretation Guide. ^Standard procedures for repeatingquestions and response choiceswêre followed, as outlined in theSF 6 Health Survey: Manual andInterpretation Guide. ^ The partici-pants were able to choose from atyped list of response choices thatwâs enlarged and placed on a tablein front of them for each question.To avoid influencing the partici-pants' answers on the SF-36, it wasthe first test given to each partici-pant on both testing days, beforethey were asked any other health-related questions.UPDRS The UPDRS subscaleswere administered as described byGoetz and colleagues,2 andaUPDRStotal score was calculated based onthe sum of the scores of the 3 sub-scales. The test was administered by1 of 2 researchers, both of whomreviewed the UPDRS teaching video-tape. Th e original 5-point (1- 5) H&YScale staging of PD was used in thestudy.s' Higher scores on the H&YScale indicate greater impairmentof PD.Data AnalysisInternal consistency and test-retestreliability were calculated using SPSS(version 15.0) software.* Internalconsistency, assessed using theCronbach alpha, was calculated formultiple-item tests, such as the BBS,ABC Scale, SF-36, and UPDRS. Inter-nal consistency of .70 or greater wasrequired on the multiple-item testbefore oth er forms of reliability wereconsidered trustworthy. The ICC(3,k) was used instead ofthePearson'SPSS Inc, 233 S Wac ker Dr, Chicago , IL60606.


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Functional Assessment in Parkinsonismcorrelation coefficient r) for test-retest reliability because it assessesrating reliability bycomparingthevariabilityof different ratingsofthesame subject with the total variationacross all ratings and all subjects. Fortest-retest reliability, eitheratype 3,1or type3,2ICC was used. The ICC(3,1) was usedfortheBBS,RT, SRT,ABCScale, 6MWT, SF-36, and UPDRSbecause final scores on these testswe re based o n a single measure fromone rater. The ICC (3,2) was used forthe TUG, forward and backwardftinctional reach, and comfortableand fast gait speeds because, finalscoresforthese tests w ere based onan averageof2 trials. Normal distri-bution wasassessed for eachout-come variableattestday 1usingahistogram plot. Data from 2partici-pantsonthe SF-36 and 1participanton the ABCScale w ere excludedfrom the data analysis due to thepresence of cognitive deficits, asjudged by the researchers adminis-teringthetests. Duetofatigue,thegait speed tests were notadminis-teredtoone participant.ResultsTable 1 reports internal consistencyfor all multiple-item tests used in thisstudy.Alltestsmet thecriterionofCronbach alpha being .70 or greater,withtheexceptionofday 1for theSocial Functioning subscale of theSF-36/ and both daysfor theMenta-tion, Behavior, and M ood subscale ofthe UPDRS. Intemal consistencyfrom previous studies also is re-portedinTable1. Inprevious stud-ies, both th eSF 36Vitality and SocialFunctioning subscales have had in-temal consistency values less than.70.Table2reports means, standard de-viations, and confidence intervalsfrom the first testing day, as wellas theICCsandMDCc,5 valuesforall testsand measures administeredin this study. The6MWT was theonly test that demonstrated statisti-

Table1.Internal Consistency for Balance Tests, a Quality-of-Life Measure, and a DiseaseSeverity Rating Scale in People With Parkinsonism (n = 36-37)

Test

Balance testsBerg Balance ScaleActivities-specific Balance Confidence Scale

36-ltem Short-Form Health Survey (SF-36)Physical Fu nctioningRole-PhysicalBodily PainGeneral HealthVitalitySocial FunctioningRole-EmotionalMental Health

Unified Parkinson Disease Rating ScaleMentation, Behavior, and MoodActivitiesofDaiiy LivingMotor ExaminationTotal score

Intern al ConsistencyCronbach forthe PresentStudyDa y

.86

.95

.85

.85

.95

.85

.85

.67

.91

.84

.64

.75

.87

.88

Da y2

.87

.96

.87

.74 91

.8091848993

678088.90

Values FromPrevious Studies

,85-.89 - 2,80 - .98 i -28 -30

3 4 _ 9365-68,70,72,73,75-798 3 - 9865-68,70,72 ,73,v 5-79i7 9 _ 9565-68,70,72,73,?5-7972_,9565-68,70,72,73,75-79

.66_9665-68,70,72,73,75-7939 _ 9865-68,7O,72,73,7 5-797 8 - 9965-68,70,72,73,75-797 2 - 9565-68,70,72,73,75-79

798085-,.9280-83

.88-.95i-8i-85

.94_,96io,86

cally higher retest values (f=2.15,P


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Functional Assessment in ParkinsonismTable2.Sample Sizes, Means, Standard Deviations, 95% Confidence Intervais (CIs), Intraclass Correlation Coefficients (ICCs) for Test-Retest Reliability, and Minimal Detectable Changes (MDCs) for Balance and Ambulation Tests, a Quality of Life Measure, and aDisease Severity Rating Scale in People With Parkinsonism

Test PerformedBalance testsBerg Balance Scale (0- 56 points)Activities-specific Balance Confidence Scale(%)Functional Reach Test (cm)

ForwardBackward

Romberg Test(s)Eyes openEyes closed

Sharpened Romberg Test(s)Eyes openEyes closed -

Ambulation testsSix-Minute Walk Test(m)Timed Up & Co Test(s)Cait speed(m/s)

ComfortableFast

36-ltem Short-Form Health Survey (0-100 points)Physical FunctioningRole-PhysicalBodily PainCeneral HealthVitality'Social FunctioningRole-EmotionalMental Health '

Unified Parkinson Disease Rating Scale (points)Mentation, Behavior,and Mood (0-16)Activitiesof Daily Living (0-52)Motor Examination (0-108)Total score (0-176)

n

3736

3736

. 3737

3737

3737

3636

3636363636363636

36363736

M e a n SD)

5 0 ( 7 )70 (19)

21 (6)14(5 )

58 (10)54(17)

39 (25)15(22)

316(142)15(10)

1.16 (.34)1.47 (.51)

57 (23)4 7 ( 4 1 )68 (27)59 (26)52 (20)83 (20)75 (40)76 (16)

2 ( 2 )12 (6 )19 (12)33(16)

9 5 % C l

47 -5264-77

18-2313-16

55-6248-60

30-478-23

269-36412-19

1.04-1.271.30-1.64

49-6533-6159-7750-6745-5976-9061-8970-81

2-310-1415-2328-38

ICC

.94

.94

.73

.67

.86

.84

.70

.91

.96

.85

.96

.97

.80

.85

.89

.85

.88

.71

.'84

.83

.89

.93

.89.91

M D C , s

513

97

1019

3919

8211

0.180.25

2845252819294519

24

1113 Means, standard deviations, and 95% CIs are from first day oftesting.'' ICC (3,1 ): Berg Balance Scale, Activities-specific Balance Confidence Scale, Romberg Test, Sharpened Rom berg Test, Six-Min ute W alk Test, 36-ltem Short-Form Health Survey, and Unified Parkinson Disease Rating Scale. ICC (3,2): Functional Reach Test, Timed Up &Co Test, and gait speed.

gramsbut may have less severePDthan patients with thedisease seenin long-term careandacute careinpatient facilities. Minimal detectablechange values could vary not only bya disease but also by stage of thedisease. The BBS,ABCScale,SRT

with eyes closed, 6MWT,andgaitspeed tests all demonstrated test-retest reliability values above.90.The MDCs calculated from thesetest-retest valuesareconsidereddependable. Functional tests with test-retest reliability values below .90

forward and backward functionalreach, RT with eyes openandeyesclosed, SRT with eyes open, TUG)shouldbeused with cautionin people with parkinsonism. All of theSF-36 subscales except the SocialFunctioning andRole-Physicalsub


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Functional Assessment in Parkinsonismscales and all ofthe UPDRSsubscalesexcept the Mentation, Behavior, andMood and ADL subscales had inter-nal consistency and test-retest reli-ability values above ,80, indicatingthat the scales measure one conceptand that the MDCs are trustworthy.Balance Tes tingInternal consistency for th e BBS inthis study w as similar to findings ofaprevious study of people with PD,ioOur stud y's high test-retest reliabilityand calculated MDC95 values weresimilar to values reported in currentliterature (2 -12) for peop le w ith var-ious disabilities,9.'3-i5,i9 An MDC95value of5on theBBSfor peop le withparkinsonism is useful to physicaltherapists.The test-retest reliability value of ,73for forward functional reach in thisstudy was within the wide range of,42 to ,93 reported in 2 previousstudies of subjects w ith PD,15,22 j h ecalculated MDC^g of 9 cm for for-ward functional reach is betweenthe values of 4 to 12 cm calculatedfrom the previous literature for sub-jects w ith PD,'5.22 The low test-retestreliability value of ,67 for backwardfimctional reach, with a calculatedMDCyj value of 7 cm, indicates thatthis test should be used with cau-tion. Our test-retest reliability valuesfor the SRT with eyes open andclosed were slightly lower than thevalues obtained for the SRT witheyes open and closed in a previousstudy of elderly women who werehealthy,'^ No previous research re-ports MDC values on these tests forindividuals with parkinsonism. Manysubjects reached the 60-second ceil-ing on the RT and SRT with eyesopen,A floor effect was seen for theSRT with eyes closed, but this testhad higher test-retest reliability val-ues than th e SRT with eyes open orthe RT with eyes open and closed.Due to the low reliability of scoresobtained for forward and back-wardfunctional reach and for the RT and

SRT (except for the SRT with eyesclosed) in this study, these testsshould be used cautiously as a mea-sure of responsiveness to change inthis population.TheABCScale had excellent internalconsistency and test-retest reliability,w^ith values being higher than thosereported in the previous litera-ture, ^^ s-30 TheMDC95value of13%in our study fell below the 18% to38% calculated from the p revious lit-erature for other patient popula-tions, A change score of 13% orgreater should be used for peoplewith parkinsonism,Amb ulation TestingThe test-retest reliability and MDCc,5values obtained for 6MWT in thisstudy fell within the range found incurrent literature,3i-'*i''3.,47,48 No^eof these studies, however, assessedindividuals with parkinsonism. TheMDCygvalue of82m w as larger thandesired due to a large standard devi-ation resulting from a wide range ofdisease severity of the participantson theH&Y,Even though the MDC95value was high, test-retest reliabilityon the 6MWT for people with PDwas excellent. Thus, anMDCc,5valueof 82 m is valid for clinicians usingth e6MWTin individuals w ith parkin-sonism. Future studies with greaternumbers of patients in each H&Ystage will determine whether thestandard deviation decreases second-ary to better homogeneity of thegroup by stage. Ifso,sep arate MDCson the 6MWT should be determinedfor each stage of the disease. Futureresearchers should check this func-tional test for learning effects. Theeffects of learning on the 6MWTfound in this study, although signifi-cant, were small,Test-retest reliability values obtainedfor the TUG in this study fell withinthe range of reliability values foundin previous research studies, '50,52The MDCyj values were higher than

desired but fell within the range ofvalues reported in the current litera-ture,5052 The mean score of 15 sec-onds on the TUG in this study wo uldmake a change score of 11 secondsor better unrealistic for the majority'of the group. An MDC study basedon each of the H&Y stages may de-crease the standard deviation andsubsequently provide lower MDCson the TUG,Test-retest reliability values for com-fortable gait speed in this study fellwithin the values previously report-edi3,2i,32,37,53,55-58,6o a n d We re h ig h e rthan the reliability values obtained inthe only other study reporting test-retest reliability for people withPD,i5 O ur calculatedMDC95value of0,18 m/s fell within the range ofvalues reported in the litera-turei321,32,37,53,55-58,60 and was simi-lar to the SDD value of ,19 m/s re-ported in a previous study of peoplewith PD,i5 The reliability and MDCc,,values obtained for fast gait speed inthe current study were similar tovalues reported in previous re-search ,^ 32,37,57,58,60 The MDCy5 val-ues calculated for the gait speed tes tsin this study are valid for individualswith PD, Of the 4 ambulation testspresented, clinicians should con-sider using both the comfortable andfast gait speeds to measure respon-siveness to change over time be-cause of the high test-retest reliabil-ity, normal distribution, and usefulMDC scores in people with PD,SF 36Internal consistency values forall 8 SF-36 subscales in this studyfell within the Cronbach alphavalues reported in previous re-search,5-68,7o,72,73,75-79 Similar toprevious research, the Social Func-tioning scale had the poorest inter-nal consistency (Tab, 1),The test-retest reliability andvalues (Tab, 1) calculated for all ofthe SF-36 subscales in this study fell


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Functional ssessment in Parkinsonism

with the ranges reported in the pre-vious literature,'^^-''''*'^^-'^^ None ofthese studies, however, assessed in-dividuals with parkinsonism. Thelarge MDC95values can be attributedto the broad diversity of populationstested. Each subscale of the SF-36can be used independently. Therapymay improve a patient's quality oflife as measured by the PhysicalFunctioning subscale (10 items) andthe Bodily Pain subscale (2 items),and these SF-36 subscales should beutilized by therapists, A change of28/100 or higher on the PhysicalFunctioning subscale and a changeof 25/100 or higher on the BodilyPain subscale would demonstrate animprovement in these quality-of-llfedimensions,UPDRSInternal consistency for the MotorExamination subscale of the UPDRSin this study wassimilar to the rangesreported in previous studies, '*'^-*''Cronbach alpha values for theUPDRS subscales and total score inthis study all fell slightly below re-ported values in the literature, w hichmay be due to the large sample sizesused in previous studies,10,82,83,86 j ^temal consistency of the Mentation,Behavior, and Mood subscale of theUPDRS was below the acceptablelevel of ,70,and this subscale shouldbe used with caution in measuringchange over time, despite accept-able test-retest scores.The test-retest reliability and MDC95values for the UPDRS subscales andtotal score were similar to values ob-tained in previous studies, 5,87,88.fj,eMDCc,5values of2for th e M entation,Behavior, and Mood subscale and 4for the ADL subscale in this studywere the same as the values obtainedfor those subscales in a previousstudy that examined 400 patientswith early stage, mild PD, but 4points higher for the Motor Exami-nation subscale and total score, ^The higher MDCpg values in this

study may have been due to thesmaller sample size and wider repre-sentation of PD severity.

ConclusionTherapists have evaluation choicesfor measuring balance, ambulation,quality of life, and disease severitywhen assessing change over time inpatients with chronic disease. TheMDCs found for theBBS,ABC Scale,SRT with eyes closed, comfortableand fast gait speeds, 6MWT, SF-36subscales (except Social Function-ing), and UPDRS ADL and Motor Ex-amination subscales and total scorewill be useful to therapists workingwith patients with parkinsonism inrehabilitation and wellness programsto determine whether change is dueto testing error o r is a result of inter-vention techniques. These valuesalso help therapists interpret litera-ture comparing statistical signifi-cance with meaningful clinicalchange, Test-retest reliability studieswith larger samples by stage of PDand for patients w^ith Parkinson-plussyndromes will help further defineMDC values.Dr Steffen provided concept/idea/researchdesign project management fund procure-ment subjects facilit ies/equipment and in-stitutiona l liaisons Ms Seney provided w rit-ing and data collection and analysisA special thanks to Rebecca Zab kow icz Sta-cey Snider Mo niq ue Serpas Travis RasinskiAsha Rani Dana Pechawer Jennifer Mi llar dAndrea Kriese Anne Haseman Nicole HaleStephanie Georgia Amy CuathierStephanie Davis Kathryn Cushman JenniferBraier and Krista Bitetto wh o assisted wit hthe literature review and data collectionwhile they were physical therapy or masterof science in rehabilitation students at Con-cordia University Wisconsin and to CherylPetersen for professional supervision on theproject.This research was presented at the Com-bined Sections Meeting of the AmericanPhysical Therapy Association; February 6-92008; Nashville Tenn

This article wasreceived July 31 2007 andwa saccepted ebruary 4 2008.DOI:10 2522/ptj 20070214

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