Table 2.

Screening test characteristics for three screening strategies for C. trachomatis and N. gonorrhoeae at the time of IUD insertion

Variables	Sensitivity % (95%CI) [# true positive/total # infected]	Specificity % (95%CI) [# true negative/total # uninfected]	NPV % (95%CI) [# true negative/# screen negative]	PPV % (95%CI) [# true positive/# screen positive]	Negative LR	Number of missed infections n (%)
Age-based (age ≤25)	80.7 (73.2, 86.4) [121/150]	48.1 (46.6, 49.5) [2372/4937]	98.8 (98.3, 99.2) [2372/2401]	4.5 (3.8, 5.4) [121/2686]	0.4	29 (19.3)
Age/Partner-based (age ≤25 and multiple sexual partners)	84.7 (77.7, 89.8) [127/150]	44.8 (43.4, 46.2) [2211/4937]	99.0 (98.5, 99.3) [2211/2234]	4.5 (3.7, 5.3) [127/2853]	0.3	23 (15.3)
Risk-based (age ≤25, multiple sexual partners, history of prior STI, and inconsistent condom use)	99.3 (99.5, 100) [149/150]	7.6 (6.8, 8.3) [375/4937]	99.7 (98.5, 99.9) [375/376]	3.2 (2.7, 3.7) [149/4711]	0.1	1 (0.7)

NPV – negative predictive value; PPV – positive predictive value; LR – likelihood ratio; STI – sexually transmitted infection