Comparision of line probe assay and conventional methos for detection of mycobacteria other than tuberculosis (MOTT) strains from patients suferring from pulmonary tuberculosis

Abstract

Introduction: MOTT infections are fatal if not treated properly which are mostly found in immunocompromised patients & are resistant to most of the antituberculosis drugs.Hence rapid identification is necessory.Line Probe Assay (LPA) allows molecular identification of Mycobacterium tuberculosis (MTB) complex and differentiates from MOTT. Aims and Objectives: To determine sensitivity & specificity of LPA for detection of MOTT strains from sputum samples in comparison to conventional tests. Methods: 105 sputums were collected from suspected cases of pulmonary TB & were microscopically examined for acid fast bacilli (AFB).They were decontaminated by NALC-NAOH method & cultured on Lowenstein Jensen medium( LJM).DNA was extracted from decontaminated sputums & LPA was carried out.For MOTT detection,MTB complex band was observed for its absence in LPA,whereas growth obsrved on LJM was tested by conventional tests like PNBA inhibition, growth in relation to temparature & speed,photoreactivity & niacin production. Results: 82% sputum were positive for AFB in ZNCF staining. Conventional methods detected 53% strains of MTB & 27% strains of MOTT while LPA detected 61% strains of MTB,34% strains of MOTT.LPA showed 100% sensitivity & 91.1% specificity ,78% Positive Predictive value & 100% negative Predictive value compared to conventional tests.Time requied for detection by conventional method was 2 wks,while by LPA was15 hours. Conclusion: LPA is found to be rapid & sensitive method for detection of MOTT strains compared to conventional methods.But is costly and requies trained personnel & proper laboratory infrastrucure.