Biologic Markers in Immunotoxicology (1992) / Chapter Skim
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8 Application of Biologic Markers of Immunotoxicity in Epidemiology
8 Application of Biologic Markers of Immunotoxicity in Epidemiology
Pages 113-126
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From page 113... ...
Epidemiologic studies have been classified into thee groups, or types: Cross-sectional studies or snapshots In time. Retrospective studies, uS',atty involving attempts to establish He fact or amount of exposure so as to relate it to current disease or disability.
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From page 114... ...
among the &eased than among the nondiseased. Some of the early work relating cigarette smoking to lung cancer proceeded along these lines.
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From page 115... ...
Laboratory sensitivity indicates the lowest level of an analyte that car be measured reliably by the analytic technique. Laboratory specificity indicates He ability of the analytic technique to exclude identification of substances other than the desired analyte.
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From page 116... ...
: S=sitiviq= 100%- 10/10 Specific= 95% - 940/990 Exposed No 100 45 145 855 855 900 1000 Positive pre~c~ve value 100/145 - 69% [:XAMPLE 3: Sac accurate test, used when mere is a higher prevalence (100 in 1,000 = 10~o3: Sequitur = 100% = 10/10 Spent ~ 95% ~ 9~/ Yes No + 100 180 280 . _ O t 720 72~ _ 900 Posture predictive value 100/280 = 35.7% = 1000 Source: Adapted from Ozonoff (1987~.
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From page 117... ...
However, in Example 3, the predictive value is less, despite high prevalence, because of the less accurate test applied. ID all three examples, lhe negative predictive value Is 100%, because Me sensitivity is 100%, meanthat "all negatives" are true negatives.
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From page 118... ...
118 MARKERS IN IMMUNOTOX[COLOGY TABLE ~2 The Interrelationship Among Prevalerlce, Smear, and SPe~51Q~ . Positive predictive values in a test with 95% specificity and Varying sensitivity for four possible exposure pre~alences Spe~ific~t~r= 9S% Sens~it:y 95~0 90% 85% 80% 75~o 70% 65% 60% Prevalence 0.0001% 0.001% 1.9 onto; 0.1% 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 16.1 1.8 1.7 1.6 15 1A 13 12 ISA 14.7 139 13 12A 11.6 10.8 68 67 65 64 63 61 ~9 57 Posture predictive Values in a test with 95% sensitive and Varying species for [our possible exposure pre~alences Sensibly- 95% Spells 95% 90% 85~o 80% 75% 70% 65% 60% Prevalence 0.0001% 0.001% 0.01% 0.19 1.9 16.1 68 0.09 0.9 8.8 51 0.06 0.6 6.0 41 0.05 05 4.6 35 0.04 OR 3.7 30 0.03 03 3.1 26 0.03 03 2.7 23 0.02 02 23 21 Source: Ozonoff (1987)
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From page 119... ...
For vague, nonspecific self-reported complaints, collimation is usually not possible; these present a very difficult problem for epidemiologic studies. STUDY DESIGN Immunologic markers can be used as dependent (outcome)
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From page 120... ...
Because such immunologic markers as the HE system have been linked to numerous diseases, they could have potential for use in field studies as markers of susceptibility. There is strong support for the use of jmmunolo~c and immunoto~c~ markers in prospective studies as early indicators of effect of xenobiotic exposure.
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From page 121... ...
Re - tries could provide researchers an opportunity to conduct prospective studies in which they could test the predictive value of some immune-system markers. Studies conducted by state public-heal agencies of nonoccupational toncant exposure have included tests for ~mmune-system markers (Bekesi et al., 1987; Wore et al., 1986; Stehr-Green et aL, 1988~.
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From page 122... ...
osure-response determ~nations. Researchers were unable to distinguish job categories on the basis of immunologic markers.
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From page 123... ...
D-con~mi~ted areas has been found to be highly correlated ante serum TCDD levels (Sweeney et al., 1990~. The well-matched control population win allow the researchers to determine valid reference ranges for this population of older, mostly white males.
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From page 124... ...
=^ed ~ aged r^s ~ T-~ho~e ~p-^ ad ~ ~ Beam ~~ any ~ ~o_o~e~ ~_' ad In.
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From page 125... ...
Biologic markers of unmunotoma~, to be used ~ epidemiologic studies, are subject: to several limitations: The predictive value of the markers should be known, and it should be high. Study populations must be large 125 enough to yield firm estimates.
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