Background The prevalence of smear negative pulmonary tuberculosis (PTB) is increasing. At many centers, active PTB suspects who are Acid-Fast Bacilli (AFB) smear negative or non-productive of sputum undergo fiber optic bronchoscopy for bronchoalveolar lavage but post bronchoscopy sputum (PBS) sampling is not routine. The aim of the study was to establish the clinical utility of PBS sampling in this subgroup of patients with active PTB.
Methods A retrospective study of all patients attending a central London University hospital with microbiologically confirmed PTB between January 2004 and December 2009. Patients who were AFB smear negative or non-productive of sputum were eligible for the study if a sputum sample was obtained within 7 days of bronchoscopy.
Results The cohort (n=50) was heterogeneous—29 were male (58%), 12 were infected with HIV (24%), 19 were of African origin (38%), 17 were white Caucasian (34%) and four were from the Indian subcontinent (8%). 15 patients (30%) converted to AFB sputum smear positivity post bronchoscopy and five patients (10%) were exclusively AFB sputum smear positive on PBS microscopy. M tuberculosis was cultured from the PBS of 40 patients (80%) and four of these (8%) were exclusively PBS culture positive (Abstract P55 Figure 1). Two of these four patients were infected with HIV.
Conclusion Sampling sputum post bronchoscopy can provide a previously underutilized method of making a rapid diagnosis of PTB and reduce the number of patients who are treated on an empiric basis, particularly in the context of sputum smear negative or non-productive disease. Importantly it can increase culture yield by up to 8% hence allowing for a greater proportion of appropriate treatment of drug resistant strains. PBS sampling is also a key infection control measure that should be considered following bronchoscopy. Further studies are now required to establish the duration of smear positivity post bronchoscopy in patients who were previously considered non-infectious but in the light of this data, we consider it best practice to only de-isolate such patients when their infective status can be ascertained with at least one post-bronchoscopy sputum sample.