Prospective evaluation of in-house polymerase chain reaction for diagnosis of mycobacterial diseases in patients with HIV infection and lung infiltrates.

SETTING: Rapid diagnosis of tuberculosis (TB) in AIDS is critical for optimal treatment to reduce mycobacterial dissemination, HIV-1 replication and mortality. The inadequate sensitivity of Ziehl-Neelsen staining and its inability to distinguish atypical mycobacteria delays accurate diagnosis.
OBJECTIVE: To evaluate the polymerase chain reaction (PCR) for diagnosis of TB in bronchoalveolar lavage (BAL), blood and extra-pulmonary samples from patients with AIDS and pulmonary infiltrates.
DESIGN: Specimens from 103 HIV-1-infected patients were prospectively analysed using bacteriological methods and IS6110-PCR. Smear-positive samples were also tested using 16S ribosomal-DNA-PCR to identify Mycobacterium avium complex (MAC) infections. Gold standard diagnosis relied on positive cultures or treatment outcome.
RESULTS: Thirty-four patients exhibited TB, one TB and MAC and four MAC. The sensitivity of IS6110-PCR was 100% in smear-positive samples, 81.8% in smear-negative BAL, 66.7% in extra-pulmonary samples and 42.9% in blood. Its specificity was 97.1% in BAL and 100% in extra-pulmonary and blood specimens. The 16S rDNA-PCR identified M. avium from all smear-positive samples that grew MAC.
CONCLUSIONS: IS6110-PCR proved useful in evaluating episodes with probable clinical diagnosis of pulmonary or mixed TB and negative smears, whereas 16S rDNA-PCR would be helpful for prompt differential diagnosis of MAC in smear-positive specimens.