Table 2.

(A) Properties of the simplified p24 antigen detection assay at different cutoff values. (B) Contingency table of NC + 5SD p24 antigen detection assay and HIV DNA PCR assay. NC: average of negative control wells; SD: standard deviation; CI: confidence interval; PCR: polymerase chain reaction.

Assay cutoff	Sensitivity (95% CI)	Specificity (95% CI)	Positive likelihood ratio (95% CI)	Negative likelihood ratio (95% CI)
(A)
2NC	0.79 (0.70,0.85)	0.96 (0.91, 0.99)	21.5 (8.2, 56.4)	0.22 (0.15, 0.32)
NC+ 0.05	0.74 (0.66,0.82)	0.95 (0.90 0.98)	16.2 (6.8, 38.4)	0.27 (0.20, 0.37)
NC+ 2SD	0.91 (0.84,0.95)	0.93 (0.86, 0.96)	12.4 (6.4, 24.3)	0.10 (0.05, 0.17)
NC+ 3SD	0.90 (0.83, 0.94)	0.95 (0.90, 0.98)	19.7 (8.3, 46.4)	0.10 (0.06, 0.18)
NC+ 5SD	0.84 (0.76,0.90)	0.98 (0.94, 1.0)	45.8 (11.6, 181)	0.16 (0.11, 0.25)

	PCR (+)	PCR (−)
(B)
p24 (+)	95	2
p24 (−)	18	107