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Interpretation of Laboratory Tests:A Case-Oriented Review of Clinical
Laboratory Diagnosis (Part 2)
Roger L. Bertholf, Ph.D.Associate Professor of Pathology
University of Florida Health Science Center/Jacksonville
Mark A. Bowman, MT(ASCP), Ph.D.Associate Professor of Clinical Pathology
Clinical Laboratory Sciences Program DirectorUniversity of Iowa College of Medicine
Case 1: Failure to Conceive
Case HistoryA couple visits their family doctor,
complaining that the wife had been unable to become pregnant.
What questions should you ask?
Infertility• Definition: One year of unprotected intercourse
without pregnancy– 1°: No previous pregnancies– 2°: Previous pregnancy (not necessarily live birth)
• Fecundability: Probability of achieving pregnancy within a menstrual cycle– 20-25% for normally fertile couples 90% of couples should conceive within one year
• 10-15% of couples experience infertility
Probabilities of failure to conceive
10
100
0 2 4 6 8 10 12
Months of unprotected intercourse
Perc
ent f
aile
d
Nulliparous
Parous
5 months
2.7 months
50
Requirements for conception• Male must produce adequate numbers of normal, motile
spermatozoa• Male must be capable of ejaculating the sperm through a
patent ductal system• The sperm must be able to traverse an unobstructed
female reproductive tract• The female must ovulate and release an ovum• The sperm must be able to fertilize the ovum• The fertilized ovum must be capable of developing and
implanting in appropriately prepared endometrium
Sperm Morphology• % normal spermatozoa• Head, acrosomal region• Vacuoles• Midpiece abnormalities• Tail defects
Comparison of CriteriaWHO (1987)
WHO (1992)
Strict (1986)
% Normal 50 30 14
Head length (m) 3.0-5.0 4.0-5.5 5.0-6.0
Head width (m) 2.0-3.0 2.5-3.5 2.5-3.5
W/L 1.5-2.0 1.5-1.75 1.0-1.67
Evaluation of semen• 2-3 days abstinence prior to collection• Gelation/liquefaction (macroscopic)• Color/volume/consistency/pH
Sperm morphology
Sperm motility
The Endocrine System
Hypothalamus/Pituitary/Pineal
Thyroid/Parathyroid
ThymusAdrenalPancreasKidney
Testis
Ovary
Evaluation of male infertility
H&P
Follow-upSemen analysis
PCTAntisperm antibodies
Sperm mucuous penetration
Repeat
LH, FSH, Testosterone
N A
N
N
A
A
Male Hypothalamic-Pituitary-Gonadal Axis
GnRH
LH, FSH
TestosteroneInhibin
FSH acts on Sertoli cellsLH acts on Leydig cells
Male reproductive endocrinology
LH FSH Testosterone Diagnosis
Hypothalamic or pituitary failure
Gonadal failure
N N Germinal compartment failure
N N or Androgen resistence
N N N Idiopathic
Causes of female infertility
Pelvic factors50%
Immunologic factors
5%
Other15% Ovulatory
disorders30%
Female Hypothalamic-Pituitary-Gonadal Axis
GnRH
LH, FSHEstradiol
Progesterone
FSH stimulates follicular growthLH stimulates ovulation
Cyclical changes in female reproductive hormones
1 4 8 12 16 20 24 28
Days since onset of menses
FSH LH Estradiol Progesterone
Ovulation
Evaluation of amenorrhea
• Vaginal• Uterine• Ovarian• Adrenal disorders• Thyroid disorders• Pituitary/hypothalamic
disorders
• Pregnancy/lactation• Uterine• Ovarian• Adrenal disorders• Thyroid disorders• Pituitary disorders• Hypothalamic disorders• Iatrogenic
Primary causes Secondary causes
Primary amenorrhea• 40% due to Turner’s syndrome or pure
gonadal dysgenesis– Turner’s syndrome: 45X karyotype– Pure GD: 46XX or XY karyotype
• Müllerian duct agenesis or dysgenesis• Testicular feminization
– Androgen receptor deficiency in XY karyotype
Secondary amenorrhea• Pregnancy is the most common cause• Prolactin elevation
– Tumor– Iatrogenic
• Thyroid disease– Effects on the metabolism of estrogens and
androgens
TRH
TSH
T4(T3)
T3(rT3)
Regulation of thyroid hormones
Thyroid disease and infertility• Hypothyroidism
– Pre-pubertal• Delayed sexual maturation, or rarely, precocious
puberty– Post-pubertal
• TSH may have leuteotropic effect
• Hyperthyroidism– Amenorrhea
Endometriosis• Appearance of endometrial tissue elsewhere
in the pelvic cavity.– Origin is uncertain
• One of the most common diseases of menstruating women
• Involved in 20-50% of infertility cases
Causes of infertility
Endometriosis5%
Seminal Defect25%
Tubal Defect22%
Other4%
Ovulation Defect27%
Unexplained17%
Unexplained infertility• Exclusionary diagnosis, after all diagnostic
tests are normal• Most studies report a 15-25% incidence• Conservative protocol:
– Semen analysis, mid-luteal phase progesterone, tubal patency
• Liberal protocol:– Above, plus cervical mucous evaluation,
endometrial maturation, immunology studies
Immunological causes of infertility
• Male or female?• Source
– Vaginal fluid (IgA, IgE)– Fallopian tubes (IgA)
• Variations throughout cycle• Experimental induction of infertility
– Baskin, 1932– Animal studies
Anti-sperm autoantibodies• 1955: Rumke and Hellinga demonstrate
association between humoral autoantibodies to sperm and unexplained infertility– Results were controversial, and hampered by
inadequate analytical techniques– Humoral antibodies do not effect fertility
unless they exist in the reproductive tract• Antibodies must be demonstrated on the
sperm surface
Effect of sperm autoantibodies• Spontantous agglutination• Motility/penetration
– Binding to tail• Disruption
– IgG mediated complement fixation (tail)– Seminal fluid contains complement inhibitors,
so membrane attack occurs in the female reproductive tract
Anti-sperm antibodies in the female
• Clinically significant only in high titers (in serum)
• Anti-sperm antibodies may exist in vaginal secretions or cervical mucus even when humoral antibodies are not detected
Diagnosis of immune-related infertility
• Post-coital test– Evaluates sperm viability in the cervical mucus
• Humoral antibodies– Not diagnostic
• Demonstration of antibodies on the sperm surface
Case 3: Unexplained Weight Loss
Case HistoryA 62 year old man visited his family doctor because of
weight loss from 185 lbs. to 163 lbs. The patient was not obese prior to his weight loss, and he described his appetite as “normal.” He had occasional indigestion. The patient was afebrile, and vital signs were normal. The patient had normal bowel movements.
What other questions would you ask this patient?
Pre-test• What are “tumor markers”?• What are desirable characteristics of a
tumor marker?• In what ways are tumor markers used?
Leading causes of death in the United States
Total Deaths Percent of total
All causes 2.391,399 100
Cardiovascular disease 725,192 30.3
Cancer 539,838 23.0
Cerebrovascular 167,366 7.0
COPD 124,181 5.2
Accidents 97,860 4.1
Source: National Vital Statistics Report (1999 data)
Types of tumor markers• Enzymes and isoenzymes• Hormones• Oncofetal antigens• Carbohydrate antigens• Receptors• Oncogene products• Genetic markers
Desirable characteristics of tumor markers
• Easy to measure• Specific for tumor• Always present with tumor
Sensitivity vs. Specificity• Sensitivity and specificity are inversely
related.
Mar
ker c
once
ntra
tion
- +Disease
Sensitivity vs. Specificity• Sensitivity and specificity are inversely
related.• How do we determine the best compromise
between sensitivity and specificity?
Receiver Operating Characteristic
True
pos
itive
rate
(sen
sitiv
ity)
False positive rate1-specificity
Evaluating the clinical performance of laboratory tests
• The sensitivity of a test indicates the likelihood that it will be positive when disease is present
• The specificity of a test indicates the likelihood that it will be negative when disease is absent
• The predictive value of a test indicates the probability that the test result, positive or negative, correctly classifies a patient
Predictive Value
The predictive value of a clinical laboratory test takes into account the prevalence of a certain disease, to quantify the probability that a positive test is associated with the disease in a randomly-selected individual, or alternatively, that a negative test is associated with health.
Illustration• Suppose you have a new marker for liver
cancer• The test correctly identified 98 of 100 patients
with confirmed liver cancer (What is the sensitivity?)
• The test was positive in 15 of 100 patients with no evidence of liver cancer (What is the specificity?)
Test performance
• The sensitivity is 98.0%• The specificity is 85%• Liver cancer has an incidence of
1.5:100,000• What happens if we screen 1 million
people?
Analysis
• In 1 million people, there will be 15 cases of liver cancer.
• Our test will (most likely) identify all of these cases (TP)
• Of the 999,985 healthy subjects, the test will be positive in 15%, or about 150,000 (FP).
Predictive value of the positive test
The predictive value is the % of all positives that are true positives:
%01.0
100000,15015
15
100
FPTPTPPV
What about the negative predictive value?
• TN = 849,985• FN = 0
%100
1000985,849
985,849
100
FNTNTNPV
Summary of predictive value
Predictive value describes the usefulness of a clinical laboratory test in the real world.
Or does it?
Lessons about predictive value
• Even when you have a very good test, it is generally not cost effective to screen for diseases which have low incidence in the general population. Exception?
• The higher the clinical suspicion, the better the predictive value of the test. Why?
Use of tumor markers• Screen for disease• Diagnosis of symptomatic patients• Staging• Prognostic indicators• Detect recurrence of disease• Monitoring response to therapy• Radioimmunolocalization
Prostate-specific antigen• A serine protease in the kallikrein family
– Produced exclusively by epithelial cells in the prostate
• Forms complexes with 1-antichymotrypisin (ACT) and 2-macroglobulin– Most immunoassays measure both free PSA and
PSA-ACT, but not PSA-AMG
Prostate cancer• 2nd most common cancer (19%), and 2nd
leading cause of cancer death, in men• Sensitivity of PSA (at 4.0 g/L) is 78%;
specificity is approximately 33%.• PSA concentration correlates with clinical
stage of cancer• PSA is used to monitor therapy
Free PSA• Measurement of uncomplexed (free) PSA
can improve the specificity– Reported as %fPSA
• Prostate cancer is associated with higher concentrations of PSA-ACT
• BPH is associated with higher free PSA concentrations
hCG• Glycoprotein secreted by the
syncytiotropoblastic cells of the placenta subunit is shared with LH, FSH, TSH subunit is specific to hCG
• Assays can measure intact (sandwich) or both intact and subunit– Cancer patients produce both intact hCG and
subunit
Use of hCG• Pregnancy• Elevated with virtually all trophoblastic
tumors– C/P Hyatidiform mole ()– Choriocarcinoma
• Elevated in 70% of nonseminomatous testicular tumors
Alpha-Fetoprotein• Major fetal protein (70 kd glycoprotein)
– Synthesized in the yolk sac, fetal liver, GI tract, kidney– Structurally related to albumin
• Used as a marker for neural tube defects• Moderate elevations in liver disease
(hepatitis/cirrhosis)• Concentrations >1000 g/L are associated with
hepatocellular carcinoma– Lower cutoff is used for screening
Combined AFP/hCG• Useful for differentiating germ cell tumors
AFP hCGYolk sac tumors nlChoriocarcinoma nl Embryonal carcinoma Seminomas nl Teratoma nl nlNonseminomatous testicular tumor or
Carcinoembryonic antigen
• Family of up to 36 large, cell-surface glycoproteins
• Elevated in . . .– 70% of colorectal cancers– 45% of lung cancers– 50% of gastric cancers– 40% of breast cancers– 55% of pancreatic cancers– 25% of ovarian cancers– 40% of uterine cancers
Use of CEA• Elevated in non-malignant conditions:
– Cirrhosis, emphysema, rectal polyps, benign breast disease, ulcerative colitis
• Most useful in staging and monitoring recurrence of disease
Carbohydrate Antigens• Glycoproteins expressed by tumor cells
(surface or excretory)• High molecular weight mucins
(mucopolysaccaride protein)
Breast cancer• Most common malignancy in U.S. women
(7% of women develop breast cancer by age 70)
• Episialin is expressed by mammary epithelium
• CA 15-3, CA 549, and CA 27.29 are three distinct epitopes on episialin
Specificity of episialin markers
Sensitivity Specificity
CA 15-3 69% Pancreatic, lung, ovarian, colorectal, liver
CA 549 77% Ovarian, prostate, lung
CA 27.29 58% 98% (FDA –approved for monitoring recurrence)
CA 125• High MW glycoprotein recognized by mAb
OC125– Isolated from a serous ovarian tumor
• Elevated in 50% of stage I ovarian cancer• Elevated in 90%+ of stage II, III, and IV• Overall, sensitivity 95%; specificity 82%;
PPV 78%; NPV 91%.
DU-PAN-2• 100-500 kd mucin (80% carbohydrate)• Found mainly in pancreatic and biliary
epithelium– Also in breast, bronchi, salivary glands, stomach,
colon, intestine• 60% sensitivity for pancreatic cancer• 45% sensitivity for biliary tract cancer• 44% sensitivity for hepatocellular carcinoma
Blood group antigens
CA 19-9 Sensitivity 80% for pancreatic cancer;, 30% for colorectal cancer
CA 19-5 GI, pancreatic, ovarian cancer
CA 50Sensitivity 90% for pancreatic cancer; as high as 73% for Duke’s stage C or D colon cancer. Also elevated in esophageal, liver, gastric cancer
CA 72-4 Sensitivity 40% in GI cancer, 40% in lung cancer, 36% in ovarian cancer
CA 242 Sensitivity 75% for pancreatic cancer, 70% for colorectal cancer, 44% for gastric cancer
Other tumor markers• Oncogenes
– ras, HER-2/neu, bcl-2, c-myc• Suppressor genes
– Retinoblastoma, p53, BRCA1 and 2• Receptors
– ER/PR
Oncogene associations
N-ras AML, neuroblastoma
K-ras Leukemia, lymphoma
c-myc B, T-cell lymphoma, small cell lung cancer
HER-2/neu Breast, ovarian, GI cancer
bcl-2 Leukemia, lymphoma
Pancreatic cancer• Fourth most common cause of cancer
deaths in men (fifth in women)– Incidence is increasing worldwide– 2:1 male preference
• Early diagnosis is unusual– Epigastric pain and significant weight loss are
the most common presenting signs• 1 year survival is <10%; 5 year is 2%.
Cancer incidence and mortality in the United States (cases per 100,000)
Males Females
Site Incidence Deaths Incidence Deaths
Lung 91.5 (2) 57.7 (1) 52.0 (2) 41.0 (1)
Prostate 160.6 (1) 33.9 (2)
Breast 1.3 0.3 131.9 (1) 28.8 (2)
Colon/rectum 67.4 (3) 26.3 (3) 49.0 (3) 18.5 (3)
Pancreas 12.1 12.2 (4) 9.5 9.3 (4)
Source: Cancer 2002;94 (1999 data)
Incidence and mortality of GI/pancreatic tumors (1999 data)
Site New Cases (est.) Deaths (actual)
Colon/rectum 129,400 57,155
Pancreas 28,600 29,081
Stomach 21,900 12,711
Esophageal 12,500 11,917
Source: SEER Cancer Statistics Review 1973-1999
Laboratory values in pancreatic cancer
• Serum amylase is usually elevated, but only after significant progression of the disease– Does not distinguish between pancreatitis and carcinoma
• At least half of pancreatic adenocarcinomas are ductal and mucin-producing– CA19-9 is the best marker (80-90% sensitivity)
• 5% are endocrine (islet cells) and may be hormone secreting– Insulinoma (β-islet cells), glucagonoma (-islet cells),
somatostatin, calcitonin, ACTH