Comparative Yield of Solid (L-J) vs Liquid (MGIT 960) Culture for Isolation of M. tuberculosis from Pleural Effusion

Abstract

Background: Tuberculous pleural effusion (TPE) presents an important diagnostic challenge due to paucibacillary infection characteristics. Precise and early identification of M. tuberculosis in pleural fluid is important for successful treatment measures. Objective: This study aims to compare the diagnostic sensitivity of solid (L-J) and liquid (MGIT 960) culture in the pleural samples of effusions. Materials and Methods: It is a cross-sectional comparative study with 183 sample size conducted in the NIDCH and SSMC & Mitford Hospital in Dhaka, within the period July 2017 to June 2018. Thoracocentesis was performed, gathering pleural fluid samples (n=183) in the cases of clinically suspected tuberculous pleural effusion (TPE) cases. Collected samples were subjected to centrifugation, and the resulting sediments inoculated onto two Lowenstein-Jensen (L-J) slants and into Mycobacteria Growth Indicator Tube (MGIT) 960. L-J slants were incubated at 37°C for a maximum of 8 weeks and checked after every week. PANTA supplementation was enriched in MGIT tubes, and fluorescence values were recorded at 42 days. Ziehl-Neelsen staining and a test to confirm MPB64 ICA were performed on positive cultures. Data analysis was done with MS Excel and SPSS version 25.0 software, and p<0.05 significance was applied. Sensitivity analysis was performed according to MGIT 960, which was called the gold standard. Results: Among the 183 suspected cases of TPE, 62.8% were males and 37.2% were females, with a male-to-female ratio of 1.7:1. The mean age of patients was 38.73±19.45 years, and the majority (41%) of the patients belonged to the age range 21-40 years. Mycobacterium tuberculosis grew more positively in liquid media of MGIT 960 (16/183; 8.7%) than in the solid medium of L-J (13/183; 7.1%). In the L-J positive cases, there were 5 grade 1+, 5 grade 2+, and 3 grade 3+. MGIT 960 revealed 13 L-J positive cases, along with 3 extra cases that were not diagnosed by L-J statistics, confirming the diagnostic yield with MGIT 960 being superior. The L-J media sensitivity and specificity, against MGIT 960, were 81.25 percent and 100 percent, respectively. Conclusion: M. tuberculosis of the pleural effusion exhibited better yield in MGIT 960. It is preferred over L-J due to better detection with TPE diagnosis. These results demonstrate that MGIT 960 has superior diagnostic accuracy to diagnose pleural tuberculosis.

J Enam Med Col 2023; 13(2): 56-61