Abstract
Background: A rapid diagnosis or exclusion of pulmonary tuberculosis (pTB) in pTB suspects with negative acid-fast-bacilli (AFB) sputum smears is at times still challenging in clinical practice.
Methods: We compared in retrospect results of Xpert MTB/Rif (single sputum or BAL specimen) nucleic acid amplification with a Mycobacterium tuberculosis-specific bronchoalveolar-lavage (BAL) Elispot in suspects of pTB with negative AFB sputum smears at a TB referral center in Germany.
Results: In 96 suspects of pTB with negative AFB sputum smears admitted from 04/2010-10/2011 in our clinic, pTB was confirmed by culture in 10 cases and clinically suspected in 9 cases. Sensitivity, specificity, positive and negative likelihood ratio were 60%, 97%, 30, 0.41 for culture confirmed cases and 42.1%, 97%, 21.1, 0.59 for all TB patients for the Xpert MTB/Rif and 80%, 62.6%, 2.1, 0.32 for culture confirmed cases and 89.4%, 62.6%, 2.4, 0.17 for all TB patients for the M. tuberculosis specific BAL-Elispot. BAL-Elispot identified 10 out of 11 patients with pTB (including 3 out of 4 patients with culture confirmed TB) with a negative Xpert MTB/Rif test.
Conclusion: A positive result of a Xpert MTB/Rif test on a sputum or BAL specimen has a very high likelihood for the diagnosis of active TB, however the sensitivity is insufficient to rule out pTB with a negative test result. BAL-Elispot identifies the majority of TB cases in suspects of pTB with negative AFB sputum smears and negative Xpert MTB/Rif test but the specificity of the BAL-Elispot is suboptimal for a confirmed diagnosis.
- © 2012 ERS