Comparison of Rapid Slide Culture with Culture in L-J Medium and MGIT for Isolating Mycobacterium tuberculosis from Bronchoalveolar Lavage Fluid

Aims: Rapid Slide Culture (RSC) was compared with the standard diagnostic strategy of simultaneous culture in Lowenstein-Jensen medium (L-J) and Mycobacterial Growth Indicator Tubes (MGIT™) with regard to diagnostic accuracy, turnaround time and cost, for isolating M. tuberculosis (MTB) from bronchoalveolar lavage (BAL) specimens. Materials and Method: Centrifuged deposits of 75 consecutive smear-positive and 75 randomly selected smear-negative BAL specimens were subjected to RSC as well as culture in both L-J and MGIT. Isolates were identified as MTB by standard methods. Results: One hundred and ten (73.3%) specimens were culture-positive by L-J and / or MGIT; 99 (90%) of these were RSC-positive too. No RSC-positive specimen was culture-negative on both L-J and MGIT. Thus, RSC demonstrated an overall sensitivity, specificity, PPV and NPV of 90%, 100%, 100% and 78% respectively. Significantly, 25 (33%) smear-negative specimens were RSC-positive, indicating the ability of RSC to isolate MTB from specimens with low bacillary loads. The mean time to positivity was seven, 35 and 24 days for RSC, L-J, and MGIT respectively. The cost per test was the equivalent of USD 1.82, 1.34, and 10.42 for RSC, L-J and MGIT respectively. Conclusion: Rapid Slide Culture proved to be a rapid, effective and low-cost method for culturing MTB from bronchoalveolar lavage fluid, when compared with conventional culture in L-J medium and MGIT. Keywords: Tuberculosis; Bronchoalveolar lavage; Diagnosis; Culture