Table 2.

Performance of Immunologic Failure Criteria to Identify Protocol-Defined Virologic Failure

		Failure
CD4 value confirmation	CD4 failure definitiona	Immunologic and virologic (a)b	Immunologic only (b)	Virologic only (c)	None (d)	Sensitivity %	Specificity %	PPV %	NPV %
Unconfirmed	Anyc	1225	1897	872	5696	58.4	75.0	39.2	86.7
	1	740	1020	1357	6573	35.3	86.6	42.0	82.9
	2	931	1362	1166	6231	44.4	82.1	40.6	84.2
	3	501	310	1596	7283	23.9	95.9	61.8	82.0
Confirmed by same definition	All by samed	579	417	1518	7176	27.6	94.5	58.1	82.5
	1	318	222	1779	7371	15.2	97.1	58.9	80.6
	2	337	209	1760	7384	16.1	97.2	61.7	80.8
	3	222	65	1875	7528	10.6	99.1	77.4	80.1
Confirmed by any definition	All by anye	594	420	1503	7173	28.3	94.5	58.6	82.7
	1	358	243	1739	7350	17.1	96.8	59.6	80.9
	2	408	257	1689	7336	19.5	96.6	61.4	81.3
	3	268	88	1829	7505	12.8	98.8	75.3	80.4

Abbreviations: NPV, negative predictive value; PPV, positive predictive value.

The row sum of the “Immunologic & virologic” and “Virologic only” failure columns (a+c = 2097) represents protocol-defined virologic failure; the denominator is the row sum of all 4 “Failure” columns (a+b+c+d = 9690).

^aCD4 failure definitions: 1, fall of CD4 count to, or below, pretherapy baseline; 2, 50% fall from on-treatment peak value; 3, persistent CD4 levels <100 cells/mm³ after at least 12 months on ART.

^bFormula used in calculations: sensitivity = a/(a+c); specificity = d/(b+d); PPV = a/(a+b); NPV = d/(c+d).

^cTotal: 3122 (32.2%).

^dTotal: 996 (10.3%).

^eTotal: 1014 (10.5%).