Prognostic value of American Thoracic Society criteria for non-tuberculous mycobacterial disease: a retrospective analysis of 120 cases with four years of follow-up.

BACKGROUND: Non-tuberculous mycobacteria (NTM) cause disease in healthy and immunocompromised patients. The American Thoracic Society (ATS) 2007 diagnostic criteria were devised to distinguish NTM disease from airway colonization. The aim of this study was to evaluate the prognostic value of the ATS criteria.
METHODS: In a 4-y follow-up study that ended on 8 June 2006, we retrospectively analyzed the symptoms, underlying diseases, and mortality of 120 adult non-HIV patients with NTM culture findings obtained between 1990 and 1998. We categorized the patients according to the 2007 ATS NTM case definition into positive and negative groups.
RESULTS: Only 61/120 patients (51%) fulfilled the ATS criteria for NTM disease. As compared to ATS-negative subjects, the ATS-positive group showed lower age, a higher proportion of females, and fewer fatal underlying diseases. Among ATS-negative subjects, 46/59 (78%) did not fulfil the microbiological criteria and 43/59 (73%) did not fulfil the radiological criteria. Mycobacterium avium complex (MAC) comprised 61% of isolations in the ATS-positive and 47% in the ATS-negative group (p = 0.15). No significant difference in median survival time was found between the groups: ATS-positive 7.4 y (95% confidence interval (CI) 0.2-14.6) and ATS-negative 5.3 y (95% CI 3.0-7.6). No significant difference was found in symptoms except fatigue, which was more common in the ATS-positive (56% vs 37%, p = 0.04). Symptoms lasted for less than a year in 48%, which suggests a more rapid disease progression than has previously been reported.
CONCLUSIONS: The fulfillment of ATS criteria was poorly associated with any difference in prognosis, and based on our findings would be a poor prognostic marker.