Diagnostic Performance of Line Probe Assay for the Diagnosis of Rifampicin and Isoniazid Resistant Tuberculosis in a Resource-Poor Country

Abstract

Background and study aim: The use of LPA is still new in Nigeria and only available in TB reference laboratories. In this study, the performance of LPA version 2.0 was evaluated for the detection of resistant to first-line anti-TB drugs. Patients and Methods: We evaluated the performance of LPA version 2.0 for the detection of rifampicin (RIF) and isoniazid (INH) resistance. Sputum samples from 223 participants were subjected to phenotypic drug susceptibility testing (PDST) and LPA. Statistical analyses included calculation of sensitivity, specificity, positive and negative predictive values. Cross tabulation was done along the kappa test to measure the degree of agreement between PDST and LPA. P-Value > 0.05 was considered significant. Results: The overall sensitivity and specificity of 89.6% (95% C.I 82.5-94.5%) and 65.4% (95% C.I 44.3-82.7%) for detection of RIF resistance; for INH they were 76.6 (95% C.I 67.5-84.5%) and 76.7% (95% C.I 49.5-82.6%); and for MDR-TB, they were 67.0% (95% C.I 56.4-76.5%) and 72.0% (95% C.I 57.6-83.7%). The kappa values were 0.53 (0.001), 0.38 (p = 0.000) and 0.36 (p = 0.000) for the detection of RIF, INH and MDR-TB. There was moderate agreement between PDST and LPA for detection of RIF (κ = 0.57; P = 0.0001), INH (κ = 0.44; P = 0.0001), MDR-TB (κ = 0.43; P = 0.001). Conclusion: The Line probe assay has good sensitivity and specificity for detecting rifampicin and isoniazid. However, the overall performance is moderate; this should be considered when interpreting the assay’s results