Predictive factors for a positive BAL Xpert MTB/RIF in BAL AFB smear negative PTB patients who are sputum scarce or AFB smear negative

Abstract

Introduction: Early diagnosis of pulmonary tuberculosis(PTB) remains a challenge as many PTB patients are sputum scarce or AFB smear negative(AFBSN).Bronchoscopy is often performed to increase PTB yields and the recent bronchoalveolar lavage(BAL) Xpert MTB/RIF is a welcome advance. It is more sensitive than BAL AFB smear but expensive.Thus, it might be cost effective if one can select patients in whom BAL Xpert MTB/RIF is likely to enhance early PTB yields. Aim: We conducted a study to evaluate the presence of any clinical or radiographic predictors for a positive(+ve) BAL Xpert MTB/RIF in BAL AFBSN PTB patients who are sputum scarce or AFBSN. Methods: This is a retrospective review of 44 culture proven PTB patients who were sputum scarce or AFBSN and had undergone prior bronchoscopy for suspected PTB. Results : 81.8% were males; average age was 51.5 years. 79.5%(35/44) of the PTB patients were BAL AFBSN. 60%(21/35) of BAL AFBSN PTB patients had a +ve BAL Xpert MTB/RIF. Univariate analysis did not find any statistically significant clinical factors such as the presence of lung disease(p=0.58), nor radiographic feature(p> 0.05) to be predictive of a +ve BAL Xpert MTB/RIF in BAL AFBSN PTB patients.However,85.7%(6/7) of BAL AFBSN PTB patients with pleural effusion had a +ve BAL Xpert MTB/RIF versus 53.8%(14/26)in those without,but numbers were too small to be significant. Conclusion: We were unable to identify any significant clinical or radiographic predictors for a +ve BAL Xpert/MTB in BAL AFBSN PTB patients who are sputum scarce or AFBSN. There is a suggestion that pleural effusion may predict a +ve BAL Xpert/MTB but this warrants further research.