Role of Bronchial Washing Gene Xpert in Sputum-Scarce Cases of Suspected Pulmonary Tuberculosis

Objective: To determine the frequency of mycobacterium tuberculosis detection, in bronchial washing in sputum-scarce cases of suspected pulmonary tuberculosis. Methods: A descriptive cross-sectional study was conducted at the Ojha Institute of Chest Diseases, Dow University of Health Sciences, Karachi, during July 2016 to December 2017. Sputum-scarce patients with suspicion of pulmonary tuberculosis were selected and underwent for bronchoscopy, detailed examination of bronchial tree was performed, and bronchial washing collected for testing of mycobacterium tuberculosis with Gene Xpert. Results: A total of 120 patients were included. In this study 55 (45.8%) patients were female and 65 (54.2%) were male with mean±SD of age was 39.9 ±14.7 years. Bronchial washing Gene Xpert for mycobacterium tuberculosis was detected in 83 (69.2%) sputum-scarce cases of suspected pulmonary tuberculosis patients. Conclusion: Bronchial washing Gene Xpert has an excellent diagnostic yield for detection of mycobacterium tuberculosis in sputum-scarce cases of suspected pulmonary tuberculosis.


INTRODUCTION
Pulmonary Tuberculosis (PTB) is a major public health problem, affecting the population world widely. Mycobacterium tuberculosis (MTB); a type of airborne bacterium is a causative agent for PTB. 1,2 Unfortunately, PTB affects one third population of the world including one third patients with active PTB. 3 In year 2014, the World Health Organization (WHO) published a global tuberculosis (TB) report, which showed 10.4 million new cases of PTB in year 2014. Tuberculosis remains a common public health hazard in the underdeveloped country like Pakistan, which is included in the top six nations of the world that makes 60% of new PTB cases. 4 PTB diagnosis is based on isolation of the organism from respiratory specimens, especially sputum samples. WHO suggests the bacteriological identification and confirmation of PTB by means of acid-fast bacilli (AFB) in respiratory specimens. 1,4 Several tests are available to confirm the disease.
Smear microscopy is still gold standard in many developing countries, but up to 22.8% cases are smear negative and has higher mortality as compared with smear positive. 5 Culture of MTB has long incubation time and limits its use in early diagnosis. 6 Only about 20-40% of PTB patients are smear positive, while the rest of the patients had either smear negative or sputum-scarce disease. [7][8][9] Thus, diagnosis in 60-80% of patients is not confirmed by routine tests. It is imperative to confirm diagnosis of PTB in these patients. Bronchoscopy with bronchial washing (BW) is needed for sputum-scarce patients to establish the diagnosis. 10 The rational of this study was to determine the frequency of detection of Mycobacterium tuberculosis in bronchial washing Gene Xpert in sputumscarce cases of suspected PTB. The utilization of this study is to identify the number of cases that are sputum-scarce yet having PTB. If the frequency of MTB on BW found to be high, not only complications related to MTB can be reduced but so is the associated morbidity and mortality. Early screening of sputum-scarce cases will help to prevent the associated complications and early management can be practiced. Local data is scarce regarding this study in the population of Sindh. This research was designed to find out the current magnitude of MTB in sputum-scarce cases. Our objective was to determine the frequency of mycobacterium tuberculosis detection, in bronchial washing in sputum-scarce cases of suspected pulmonary tuberculosis.

METHODS
This cross-sectional research was designed and conducted at a tertiary care teaching hospital, during July 2016 to December 2017. Non-probability consecutive method was used for selection of patients. The ethical approval of study was done from Institutional Review Board of our University. Inclusion Criteria: Patients having age between 18 to 60 years, either male or female, with suspected PTB with sputum-scarce as per operational definitions, taking anti-TB medications less than 1 week, and naive were included in the study. Exclusion Criteria: Patients with disseminated or extra pulmonary tuberculosis, HIV positive and immunocompromised patients were excluded from the study.
A written informed consent was obtained from the patient undergoing bronchoscopy procedure. Patients fulfilling the inclusion criteria were selected. Taking detailed history regarding cough, fever and loss of weight, thorough physical examination and routine investigations, assessment for the fitness of patients for the bronchoscopy procedure was performed. Details regarding educational status were recorded. Bronchoscope was introduced through trans-nasal route after proper lubrication with xylocaine ointment. Detailed examination of bronchial tree was performed, and BW was collected and sent to the laboratory for Gene Xpert, and presence or absence of MTB was recorded. For data analysis Statistical Package for Social Science (SPSS) software version 22 was used. P-value of ≤0.05 was taken as significant.
Sample size was calculated by using the proportions as reported by Khalil KF et al., 11 93 patients with suspected PTB who were sputum-sarce were subjected to bronchoscopy. PTB was confirmed by bronchial wash Gene Xpert in 81, p = 87.09% of them, with 95% confidential interval and 6% of margin of error, the sample size stands n = 120. Operational Definition Suspected PTB: PTB diagnosis is suspected from a combination of: Symptoms: Cough with sputum, fever (more than 98.4 °F), sweating and shortness of breathing Signs: Respiratory rate more than 20 per minute, weight loss (>5% of body weight over 6 to 12 months) Chest Radiograph: Consolidation, Cavitation, Nodular opacity and military shadows.
Presence of ≥ 2 clinical features of > 2 weeks duration with any of these chest X-ray findings in smear negative cases, are known as Suspected Pulmonary Tuberculosis cases. Sputum-Scarce patients: 11 Patients that had sputum amount less than 1 ml were defined to have sputum-Scarce patients.

RESULTS
In this study 120 patients were included. Mean±SD of age was 39.9 ±14.7 years, duration of symptoms was 5.4 ±2.9 weeks and duration of ATT was 3.5 ±3.1days. Out of 120 selected patients 55 (45.8%) patients were female and 65 (54.2%) were male. Selected patients were segregated into following age groups; 18 Bronchial Wash Gene Xpert for MTB results were cross tabulated with different effect modifiers such as gender, age, socio-economic status, educational status, duration of symptoms and ATT. Differences in frequency according to these effect modifiers was assessed by χ 2 test. No significant difference was observed in frequency according to the effect modifiers. Details are given in Table-I.

DISCUSSION
Tuberculosis is still a major global health problem, affecting millions every year in developing countries. TB is ranked as the second leading cause of death worldwide from an infectious cause, after HIV. TB mortality remains unacceptably high given that most deaths are preventable, if they have access to health care for a timely diagnosis and the proper treatment. 12 In our study, we determined the frequency of detection of Mycobacterium tuberculosis in BW Gene Xpert in sputum-sarce cases of suspected pulmonary tuberculosis. Many sputum smear negative patients are reported to have progressive disease. 13,14 Previous reports in non-immune compromised patients with sputum sputum-scarce TB indicated that bronchoscope specimens and post bronchoscope sputum are helpful in establishing the diagnosis. 9  patients. [16][17][18] Different studies validated the practical and clinical importance of bronchoscopy in PTB diagnosis. 10,15,16,18,19 In all these studies bronchoscopies and BW showed increased detection of TB. Bronchoscopy with BW under local anesthesia is a relatively safe procedure and well tolerated by most of the patients. Complications are rare in occurrence. 20 As all patients are sputum-scarce, delay in diagnosis in this subset often leads to increased morbidity and mortality, BW Gene Xpert can rapidly detect the MTB and rule out rifampicin resistance on the same day, helping in the early diagnosis and management of these patients. [21][22][23] In our study 37 patients were negative for MTB on BW Gene Xpert and such patients should be subjected to AFB culture to confirm PTB.

CONCLUSION
Bronchial washing Gene Xpert has an excellent diagnostic yield for detection of MTB in sputumscarce cases of suspected PTB. In our study we were able to make diagnosis of PTB in 69.2% of patients who were not able to produce sputum.