Table 2

Evaluation of the ligase chain reaction (LCx) assay in clinically resolved cases of Mycobacterium tuberculosis infection (culture results and clinical data)

No. resolved as positive for M tuberculosis (n = 164)No. resolved as negative for M tuberculosis (n = 1956)
Specimens (n = 2120)LCx positiveLCx negativeLCx positiveLCx negative Sensitivity (%)Specificity (%)PPV (%)NPV (%)
*Sixty eight were contaminated cultures.
**Nine were positive by culture for non-tuberculous mycobacteria; six were culture negative.
NPV, negative predictive value; PPV, positive predictive value.
All (2120)1422201956*88.2100.0100.098.9
Smear positive (114)9810 15**99.0100.0100.093.8
Smear negative (2006)44210194175.6100.0100.098.9
Respiratory (2058)1242201913*86.9100.0100.098.9
Non-respiratory (49)5104385.7100.0100.097.7
Quality control (13)10003100.0100.0100.0100.0