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

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.