Comparison of approaches to estimate confidence intervals of post-test probabilities of diagnostic test results in a nested case-control study

Table 1 Estimates of diagnostic accuracy of the D-dimer test and the calf-difference test in the source population for different values of the prevalence of deep venous thrombosis (DVT)

Prevalence of DVT	PPV*	NPV*	Sensitivity	Specificity	DOR	Positive test result (%)
D-dimer test (dichotomous)
0.05	0.07	0.99	0.96	0.32	10.7	69
0.1	0.14	0.99	0.97	0.33	9.2	70
0.2	0.26	0.97	0.96	0.33	11.9	73
Calf-difference test (dichotomous)
0.05	0.09	0.98	0.69	0.65	4.0	37
0.1	0.17	0.95	0.68	0.64	3.1	39
0.2	0.32	0.89	0.67	0.65	3.8	41

* Estimates of PPV and NPV obtained with the weighted formula, with Mercaldo’s approach and with weighted logistic regression were the same
(PPV = positive predictive value; NPV = negative predictive value, DOR=Diagnostic Odds Ratio).