"Identification of Non-Tuberculous Mycobacterium by LPA (CM/AS) assay, HPLC and biochemical test: which is feasible...

Non-tuberculous mycobacteria (NTM) causing clinical disease have become increasingly common and more diverse. The development of fast, inexpensive, and reliable tests to identify nontuberculous mycobacteria is need of the hour especially under the Revised National TB Control Programme (RNTCP). The Aim of the study was to check the Diagnostic efficacy of the GenoType Mycobacterium CM/AS assay compared with HPLC and Biochemical Test for Identification of Non-Tuberculous Mycobacteria under the Revised Tuberculosis Control Programme.

It is a cross-sectional study, the suspected NTM culture isolates from the RNTCP accredited laboratories were sent to NRL for speciation and Identification. The culture positive isolates were subjected to Biochemical Identification Test, HPLC and LPA CM/AS. The LPA had 98.23% sensitivity, 50% specificity, 99.56% positive predictive value (PPV) and 20% Negative predictive value (NPV) when compared to HPLC considering Biochemical test as Gold reference standard. The comparison of HPLC and LPA for identification of each species using Mc Nemers Chi square test shown no significant difference between these tests.

Considering Cost, Time and ease of performing the techniques, we recommend first do the basic biochemical test to rule out MTBC from NTM. Then do HPLC and further if results are unclear do LPA CM/AS kit for species confirmation.

NTM are emerging as important causative agents of pulmonary and extra pulmonary disease, the ability to recognize disease caused by NTM and subsequently treat such disease has become increasingly important. The identification of NTM up to its species level using HPLC and LPA CM/AS should gain importance in all TB reference Laboratories.