Evaluation of sensitivity and specificity of GenoType MTBDRplus line probe assay in rapid diagnosis of tuberculous pleural effusion

BackgroundPakistan has an annual tuberculosis (TB) incidence rate of 233 per 100,000 population and ranks sixth among the high TB burden countries worldwide. Tuberculous pleural effusion (TPE) occurs in up to 25% of TB patients. Owing to the pauci-bacillary nature of the pleural fluid, the diagnosis of TPE is a challenge.ObjectiveThe aim of the present study is to evaluate the performance of MTBDRplus line probe assay in terms of its sensitivity and specificity for the rapid TB diagnosis in TPE and frequency of multidrug-resistant TB (MDR-TB) in TPE through the detection of rifampicin (Rif) and isoniazid (INH) resistance.MethodsThis study is an ongoing prospective cross-sectional study being performed at Aga Khan University Hospital. Patients aged 18years or more with suspected TPE were asked to participate. In addition to a preformed questionnaire which gathered information regarding clinical history and previous laboratory investigations, already tapped pleural effusion samples are tested for pleural fluid composition, TB smear and culture, MTBDRplus line probe assay and ADA analysis.ResultsSo far, 22 patients with a mean age of 49.81±21.75 (range: 18–86; IQR: 29.25, 68.00) years have been enrolled. Almost two-thirds are males (n=15, 68.2%). The majority of the patient population belongs to Karachi (n=18, 81.8%), followed by Quetta (n=2, 9.1%), Faisalabad (n=1, 4.5%) and Sukkur (n=1, 4.5%). Half of the patients had a history of TB contact (n=11, 50.0%), whereas only two (9.1%) had a past history of TB. Fifty percent (n=11) had a right-sided pleural effusion. Effusion size was moderate in 36.4% (n=8), mild in 27.3% (n=6) and massive in 22.5% (n=5). Pleural fluid MTBDRplus positively detected TB in 9.1% (n=2) of cases. INH resistance was detected in one of these two cases. Pleural fluid culture was positive in two cases. Pleural fluid AFB smear was negative in all cases.ConclusionGiven the study is still under way, it is hoped that the results of this study may investigate the relevance, sensitivity and specificity of MTBDRplus line probe assay as a tool in the rapid detection of MTB in TPE and the early detection of MDR-TB through the detection of Rif and INH resistance. It may also provide an estimate of prevalence of drug resistant strains in TPE, which would be useful for guiding empirical anti-tuberculous therapy in TPE