Appraising Evidence into Appraising Evidence into our Practiceour Practice

Objectives Objectives

• Deciding the research result into practice in specific context

• Interpreting/calculating Number Needed to Treat (NTT)

• Interpreting pre and post test

• Interpreting/calculating Number Needed to Harm (NHH)

Introduction Introduction

• Health related research takes places over the world

• Specific situation or patient where the study was taking place probably different with the current situation

• Sample population characteristic ?

• Standard of services ?

Assessing ApplicabilityAssessing Applicability

Are the Findings Applicable inMy setting?

What do The resultMean for my

Patient?

Is the quality of the Study good enough

to use the result?

Factors to consider when Factors to consider when assessing applicabilityassessing applicability

Characteristic of the participant: co Characteristic of the participant: co morbidity, severity, gendermorbidity, severity, gender

Feasibility to introduce the Feasibility to introduce the intervention: specialist unit, generalist intervention: specialist unit, generalist unit, management system?unit, management system?

Think about cost and benefitThink about cost and benefit Patients preference. Forcing patient to Patients preference. Forcing patient to

accept the intervention is unethical.accept the intervention is unethical.

Meaning the Result StudyMeaning the Result Study

Quality of the study design is the Quality of the study design is the most important thingmost important thing

Avoiding the result by chanceAvoiding the result by chance ℘℘ < 0.001. (probability by chance < < 0.001. (probability by chance <

1 in 1000)1 in 1000) Number needed to treat (NNT) is Number needed to treat (NNT) is

useful for interpreting the useful for interpreting the effectivenesseffectiveness

ExampleExample

PatientPatient: Sandra, 11 y.o with 4 : Sandra, 11 y.o with 4 admission within 6 monthadmission within 6 month

EBP QuestionEBP Question: Does a structured : Does a structured nurse-lead discharge package result nurse-lead discharge package result reduce level of readmission in reduce level of readmission in children with acute asthma?children with acute asthma?

EvidenceEvidence: Wisendly, C (1999) Stucture : Wisendly, C (1999) Stucture discharge procedure for childern with discharge procedure for childern with acute asthma: an RCT study. Journal acute asthma: an RCT study. Journal of children nursing 4 (40):77of children nursing 4 (40):77

Example Example

Result ReportResult Report: Reduction in admission : Reduction in admission at 6 month.at 6 month.

Control group: 30 of 80Control group: 30 of 80

Intervention group: 12 of 80Intervention group: 12 of 80

Make 2 x 2 Table

Outcome:Readmission within 6 month

TotalGroup Study

Present Absent

Intervention 12 a b 68 a + b = 80Control 30 c d 50 c + d = 80

Total 42 (a + c) (b + d) 118 a + b+ c + d = 160

Calculating NNTCalculating NNT

Step Step MeasureMeasure Formula Formula Example Example

11

22

33

44

Experiment even Experiment even rate (EER)rate (EER)

Control even rateControl even rate

(CER)(CER)

Absolute risk Absolute risk reducation (ARR)reducation (ARR)

NNTNNT

a/a + ba/a + b

c/c + dc/c + d

CER – EERCER – EER

100/AAR100/AAR

12/12 + 68 12/12 + 68 = 15%= 15%

30/30 + 50 30/30 + 50 = 37%= 37%

37-15=22%37-15=22%

100/22 = 5100/22 = 5(rounded up)(rounded up)

The MeanThe Mean

NNT = 5 means,NNT = 5 means,

5 children need to received structured 5 children need to received structured discharge package to prevent one extra discharge package to prevent one extra child from being readmitted if they had child from being readmitted if they had received standard care.received standard care.

Number Needed to HarmNumber Needed to Harm

PatientPatient: florence, 33, using oral contraception, : florence, 33, using oral contraception, smoke 20-30 cigarettes/day.smoke 20-30 cigarettes/day.

Clinical questionClinical question: are women who smoke with oral : are women who smoke with oral contraception at higher risk of myocardial contraception at higher risk of myocardial infarction comparing with non smoker?infarction comparing with non smoker?

EvidenceEvidence: Matt, J (1999)Risk of myocardial : Matt, J (1999)Risk of myocardial infarction and angina in users of oral infarction and angina in users of oral contraception. Update analysis of Cohort study. contraception. Update analysis of Cohort study. British journal of obstetric 3(90)pp1-5British journal of obstetric 3(90)pp1-5

Number Needed to HarmNumber Needed to Harm

ResultResult: In heavy smokers there is a fourfold : In heavy smokers there is a fourfold in the risk of myocardial infarction if the pill in the risk of myocardial infarction if the pill of oral contraception is taken. 0,24 per of oral contraception is taken. 0,24 per 1000 women/year in heavy smoker who 1000 women/year in heavy smoker who never used oral contraception to 1,18 per never used oral contraception to 1,18 per 1000 women at risk in current users of oral 1000 women at risk in current users of oral contraception. contraception. Heavy smoker relative risk Heavy smoker relative risk is 4.0 for ex user of oral contraceptive pill, is 4.0 for ex user of oral contraceptive pill, 4.2 for ever-user and 4.9 for current user4.2 for ever-user and 4.9 for current user

Calculating NNHCalculating NNH

Adverse Outcome:Myocardial infacrtion

TotalGroup Study

Present Absent

Yes: heavy smoker + oral cont

a b a / (a+ b) = rate in yes group

No: Non smoker + No oral cont

c d c / (c + d = Rate in no grup

CalculationCalculation

MeasureMeasure Formula Formula Example Example

Relative risk Relative risk (RR)(RR)

Absolute risk Absolute risk increase (ARI)increase (ARI)

Number needed Number needed to harm (NNH)to harm (NNH)

a/(a+b)a/(a+b)

c/(c+d)c/(c+d)

a/(a+b)-c/(c+d)a/(a+b)-c/(c+d)

1/ARI1/ARI

1.18/0.24 = 0.491.18/0.24 = 0.49

1.18-0.24=0.94 1.18-0.24=0.94 per 1000 personper 1000 person

1/0.00094=10631/0.00094=1063

The MeanThe Mean

The number of women who smoke heavily The number of women who smoke heavily that would have to take oral contraception that would have to take oral contraception for 1 year to cause one extra myocardial for 1 year to cause one extra myocardial infarction.infarction.

In this study, a total 1063 heavy smoker In this study, a total 1063 heavy smoker would need to take oral contraception for 1 would need to take oral contraception for 1 year for 1 extra women to experience a year for 1 extra women to experience a myocardial infarction.myocardial infarction.

Conclusion Conclusion

Are the Findings Applicable inMy setting?

What do The resultMean for my

Patient?

Is the quality of the Study good enough

to use the result?

Conclusion Conclusion

We know the patientWe know the patient

We can compare the evidence with the We can compare the evidence with the local situationlocal situation

Cost and benefit should be considerCost and benefit should be consider

However, there are no perfect study as However, there are no perfect study as every design has they own limitationevery design has they own limitation

Developing Guideline Developing Guideline

Level of Level of Evidence Evidence

& & RecomendationRecomendation