Table 3

Performance of the ligase chain reaction (LCx) assay compared with culture and microscopy in clinically resolved cases of tuberculosis (TB)

Clinical diagnosis
Test method and outcome (no.)*TB+ (n = 164)TB− (n = 1956) Sensitivity (%)Specificity (%)PPV (%)NPV (%)
*Includes specimens subject to repeat testing after diagnosis and initiation of treatment.
**LCx is more sensitive than culture because patients on treatment who become culture negative remain LCx positive.
NPV, negative predictive value; PPV, positive predictive value.
LCx assay
Positive (142)142088.2**100.00100.0098.9
Negative (1978)221956
Auramine staining
Positive (114)991560.499.291.696.8
Negative (2006)651941
Positive (131)131083.2**100.00100.0098.3
Negative (1989)331956