CULTURE RESULT DISCREPANCY BETWEEN LABORATORIES FOR NON-TB MYCOBACTERIA IN PATIENTS WITH CYSTIC FIBROSIS

TYPE: Abstract TOPIC: Chest Infections PURPOSE: The increase in prevalence of NTM in our pediatric CF center is worrisome, and thus, correct laboratory diagnosis is important. Our goal was to ascertain the reliability of diagnostic tests in a teaching hospital (A) and a referral commercial laboratory (B), and compare their results obtained to a specialized laboratory for NTM (C). METHODS: We obtained 19 samples (bronchoalveolar lavage [BAL] and/or sputum) for acid-fast bacilli (AFB) from patients with suspected or known NTM. Identical samples were contemporaneously sent to A and/or B, and all sent to C. All cultures were followed for up to 56 days. One sample was lost in shipping to C and removed from analysis. RESULTS: Eight of 18 samples grew NTM in at least one laboratory. Fifty percent of the positive samples for NTM had discrepancies. Two samples (11.1% of total) sent to A or B failed to grow NTM when compared to C, and 2 samples (11.1% of total) had growth at both B and C but revealed different species. Additionally, B failed to report antimicrobial susceptibility testing (AST) results in three/four of its positive samples. CONCLUSIONS: We found discrepancies in 22.2% of AFB culture results from CF-patients when comparing duplicate BAL or sputum samples between A and/or B and C. Final speciation for Mycobacterium avium complex and subspeciation of Mycobacterium abscessus are recommended by professional societies. CLINICAL IMPLICATIONS: NTM infected CF-patients may be at risk of being underdiagnosed or being inappropriately treated when relying on culture and AST results from non-specialized laboratories. DISCLOSURE: Nothing to declare. KEYWORD: Cystic Fibrosis