Evaluation of the performance of an in-house duplex PCR assay targeting the IS6110 and rpoB genes for tuberculosis diagnosis in Cameroon

Table 4 Values of diagnostic accuracy with CRS as standard

	Diagnostic Methods
Parameters	Direct microscopy	Concentrated microscopy	LJ Culture n = 123^a	*rpoB*	*IS6110*	D-PCR
No. of samples positive	47	49	51	57	61	62
No. of samples negative	82	80	72	72	68	67
Measures of diagnostic accuracy
Sensitivity (%)	75.8	79.0	83.6	87.1	91.9	93.5
Specificity (%)	100	100	100	94.0	94.0	94.0
PPV	1	1	1	0.93	0.93	0.94
NPV	0.82	0.84	0.86	0.89	0.93	0.94
LR+	∞	∞	∞	14.5	15.3	15.6
LR-	0.242	0.21	0.16	0.14	0.02	0.005

PPV (positive predictive value); NPV (negative predictive value); LR+ (positive likelihood ratio); LR- (negative likelihood ratio). ^a excluding contaminated cultures

ISSN: 1471-2334