The effect of disease misclassification on the ability to detect a gene-environment interaction: implications of the specificity of case definitions for research on Gulf War illness

Table 3 Quantitative estimates of the levels and consequences of disease misclassification by GWI case definitions (calculations explained in Table S22)

Case definition	Sensitivity (95% CI)	Specificity (95% CI)	Population prevalence rate of diagnosed cases (%)	Population prevalence rate of true positive cases (%)	Percentage of diagnosed cases that are falsely positive (%)	Percentage of true cases that are falsely negative (%)
CDC	1^a	0.82 (0.78–0.86)	41.7	34.2	18.1	0
Modified Kansas without exclusions	1^a	0.84 (0.80–0.88)	39.0	32.7	16.1	0
Modified Kansas with exclusions	0.59 (0.55–0.63)	0.79 (0.74–0.82)	25.6	20.1	21.4	41.1
Research	0.40 (0.36–0.43)	1^b^,c	13.6	13.6	0	60.2
CDC Severe	0.31 (0.28–0.35)	1^c	10.6	10.6	0	69.0

^aPerfect sensitivity was assumed from cases satisfying the case definition with only 2 or 3 GWI symptoms, respectively
^bPerfect specificity was assumed from the Research case definition’s requiring high-threshold fit to data-derived GWI symptom patterns developed with principal components analysis of symptom scales
^cPerfect specificity was found in sensitivity analysis

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