Microbiological criteria in non-tuberculous mycobacteria pulmonary disease: a tool for diagnosis and epidemiology

SETTING: The value of microbiological criteria in diagnosing non-tuberculous mycobacteria pulmonary disease (NTM-PD) and monitoring its epidemiology is unknown. OBJECTIVES: To correlate the rate of NTM-PD based on microbiological criteria (American Thoracic Society/Infectious Diseases Society of America [ATS/IDSA] or stricter microbiological criteria) compared with the full ATS/IDSA criteria, to assess the positive predictive value (PPV) of different microbiological criteria in predicting NTM-PD, and to evaluate the clinical relevance of different NTM species. DESIGN: Retrospective study of all patients with pulmonary NTM isolates in Croatia during an 8-year period. NTM species were divided into low, intermediate and high clinical relevance groups for additional analyses. RESULTS: Good correlation between both microbiological and full ATS/IDSA criteria was observed. The PPV of stricter and ATS/IDSA microbiological criteria was respectively 93.3% and 59.8%. The usefulness of microbiological criteria varied between groups. ATS/ IDSA microbiological criteria had a PPV of 89.8% in the high relevance group, while in the intermediate relevance group, the PPV of stricter and ATS/IDSA microbiological criteria was respectively 94.3% and 63.4%. CONCLUSIONS: Microbiological criteria are useful in detecting NTM-PD, allowing laboratory-based monitoring. Stricter criteria should be used for species of low clinical relevance, and less stringent criteria for species of high relevance in the local setting.