Misdiagnosis and clinical significance of non-tuberculous mycobacteria in Western Kenya in the era of human immunodeficiency virus epidemic

Abstract

Objectives: To determine and document the role of non-tuberculous mycobacteria (NTM) in TB-like disease morbidity and demonstrate the confusion they cause in the diagnosis of TB in western Kenya. Design: A cross-sectional study. Setting: One provincial and nine District hospitals in western Kenya. Subjects: Tuberculosis suspects. Interventions: Sputa from 872 tuberculosis suspects underwent microscopy and culture on solid and liquid media. The growth was identified using the Hain’s GenoType ® Mycobacterium CM and GenoType ® Mycobacterium AS kits. Consenting clients were screened for HIV infection using Trinity Biotech Uni-Gold TM test and positive cases were confirmed with the enzyme linked immunosorbent assay. A questionnaire was used to obtain demographic data. Main outcome measures: ZN smear positivity / negativity; Culture positivity or negativity; Mycobacterium species isolates (tuberculous or non-tuberculous); HIV status. Results: Sputa from 39.1% (341/872) of the participants were ZN smear positive, of these 53.1% (181/341) were culture positive. Only 3.8% (20/531) of the ZN smear negatives were culture positive. In total 41.4% (361/872) participants were infected with mycobacteria, of which 44.3% (160/361) were culture negative and 55.7% (201/361) were culture positive. The culture positives yielded 92.5% M. tuberculosis complex and 7.5% NTM. The overall prevalence of the NTM disease was 1.72% (15/872). Conclusion: A low prevalence of NTM pulmonary disease in western Kenya is reported in this study, but some the NTM disease cases could have been misdiagnosed as TB cases.