INTRODUCTION

The Xpert MTB/RIF assay is a rapid and simple technique with high sensitivity and specificity for diagnosing TB and detecting drug resistance in extra pulmonary and smear-negative TB cases [3] and from Bronchoalveolar lavage [4,5]. With the advent of fibre-optic bronchoscopy, smear and culture for mycobacteria from the bronchial aspirate, bronchial brushing, bronchial washing, bronchoalveolar lavage fluid, post bronchoscopy sputum and biopsy material have all been used in various studies for diagnosing pulmonary tuberculosis. There are limited studies to demonstrate the use of Xpert MTB/RIF performed on bronchial lavage specimens in our settings. Hence we conducted this study to evaluate the significance of Xpert MTB/RIF performed on bronchial washing fluid obtained bronchoscopically from patients with a clinical and radiological suspicion of pulmonary tuberculosis.

METHODS

Study population

We retrospectively reviewed the clinical records and fibre optic bronchoscope (FOB) results of all patients with suspected PTB who visited the pulmonary clinic of Government Rajaji Hospital (GRH), Madurai from January 2017 to June 2017.

For the purposes of our study we considered a clinical suspicion of pulmonary tuberculosis if any two of the following were present: known HIV infection, persistent cough lasting >3 weeks, hemoptysis, weight loss >4 kg, intermittent fever >3 weeks or drenching night sweats >2 weeks. In addition, at least one of the following radiological criteria had to be present for inclusion: cavitation, diffuse infiltrates, hilar or mediastinal adenopathy. All had 2 early morning sputum smears negative for AFB by fluorescent microscope stain. They had no response to 2 weeks antibiotics used for lower respiratory tract infection. The study was approved by the Hospital Ethics Committee. A waiver of consent was obtained due to the retrospective nature of the study.

Procedure

Bronchoscopic procedure was performed according to our institute’s infection regulation and instruction guideline. The patients were informed about the procedure and consents were obtained. The patients underwent bronchoscopy by flexible fiberoptic bronchoscope through trans nasal route in supine position and under local anaesthesia. All the patients underwent continuous monitoring of electrocardiogram, blood pressure and pulse oximetry. After inspection of the bronchial tree, BAL was done with 100 ml of normal saline at the end of bronchoscopy in the region suspected for lesion based on chest radiography. The patients were observed in the recovery room. BAL samples were sent for fluorescent microscope stain, fungal smear, and cytopathology. Proper disinfection of the bronchoscope in between use was done. All Xpert MTB/RIF samples were processed according to the manufacturer’s specifications.

RESULTS

All the records were scrutinized, checked and computerized by trained data entry operators. Data entry was done in Excel 2013 and analysis was performed using SPSS 20. Descriptive statistics were performed. The study involved the patients attending the TB clinic in GRH, who had clinical and radiological findings suggestive for PTB, whose sputum smear were negative by fluorescent microscopy and a FBO was performed for TB diagnosis. A total of 100 sputum smear-negative patients were posted for FOB, 71 men (71%) and 29 women (29%), the median age was 53 years. The patients aged 41 to 60 years (53.5%) were the ages most frequently encountered (Table 1). Twenty two out of the 100 BAL specimens (22.7%) were positive culture for M. tuberculosis by Xpert MTB/RIF. Drug sensitivity test showed one case (4.5%) resistant to Rifamycin who was referred to initiate on multi-drug resistant TB treatment.

DISCUSSION

Fiberoptic bronchoscopy (FOB) is an alternative option to provide respiratory specimens for diagnosis, particularly from sites which are suspected by radiological findings to be involved in PTB after sputum expectoration has continually failed because of lacking sputum. We evaluated the clinical value of Xpert MTB/RIF assays for the diagnosis of active PTB in sputum-scarce PTB suspects in TB endemic setting.

In our study bronchial washings Xpert was positive for acid fast bacilli in 22.7% patients which were missed in smear microscopy. Although sputum microscopy is the most appropriate, low cost, highly specific investigation to diagnose pulmonary tuberculosis, Sputum smear-negative pulmonary tuberculosis (SSN-PTB) still remains a common problem faced by the clinicians. Despite being less infectious than sputum smear-positive PTB, smear-negative PTB serves as an important cause of transmission in communities by delaying diagnosis and precluding initiation of treatment and often leads to complications of irreversible lung damage in infected individuals. Diagnosis of sputum smear-negative pulmonary tuberculosis patients can be both challenging and time consuming with many patients being put on empirical anti-tubercular treatment. Therefore, sputum smear-negative PTB often requires more invasive diagnostic tools to be distinguished from other diseases such as  lung  cancer.  Fibreoptic  bronchoscopy  may  provide  a DISCUSSION

Fiberoptic bronchoscopy (FOB) is an alternative option to provide respiratory specimens for diagnosis, particularly from sites which are suspected by radiological findings to be involved in PTB after sputum expectoration has continually failed because of lacking sputum. We evaluated the clinical value of Xpert MTB/RIF assays for the diagnosis of active PTB in sputum-scarce PTB suspects in TB endemic setting.

In our study bronchial washings Xpert was positive for acid fast bacilli in 22.7% patients which were missed in smear microscopy. Although sputum microscopy is the most appropriate, low cost, highly specific investigation to diagnose pulmonary tuberculosis, Sputum smear-negative pulmonary tuberculosis (SSN-PTB) still remains a common problem faced by the clinicians. Despite being less infectious than sputum smear-positive PTB, smear-negative PTB serves as an important cause of transmission in communities by delaying diagnosis and precluding initiation of treatment and often leads to complications of irreversible lung damage in infected individuals. Diagnosis of sputum smear-negative pulmonary tuberculosis patients can be both challenging and time consuming with many patients being put on empirical anti-tubercular treatment. Therefore, sputum smear-negative PTB often requires more invasive diagnostic tools to be distinguished from other diseases such as lung cancer. Fibreoptic bronchoscopy may provide a confirmative and early diagnosis in such patients [6].