Comparative Analysis of the Diagnostic Role of Induced Sputum Versus Expectorated Sputum in Patients with Presumptive Diagnosis of Tuberculosis

Abstract

Tuberculosis (TB) is an infectious disease caused by Mycobacterium Tuberculosis (MTB). The World Health Organization (WHO) 2010 endorsed the GeneXpert test for use in endemic countries and declared it a major milestone for global TB diagnosis.1 However, its ability to detect MTB is affected by the quality of sputum produced by the patients. Inadequate case detection of TB can increase transmission and death from tuberculosis in Nigeria. The utility of sputum induction in improving the diagnosis of TB in the Nigerian context has not been extensively evaluated. AIM To investigate the diagnostic yield of induced sputum compared to expectorated sputum amongst patients in whom TB is considered based on clinical features, that present with scarce sputum or an initial negative GeneXpert sputum. METHODS This was a cross-sectional study. The participants were patients who consented, >18 years, had no previous TB treatment, presenting with cough> 2weeks, + sputum,weight loss, fever, night-sweats and had radiological imaging suggestive of TB (upper zone consolidation, cavitations, pulmonary nodules, hilar nodes,military pattern). Their radiological imaging was viewed under the supervision of a radiologist. A structured questionnaire was used to collect relevant sociodemographic and clinical information. Sputum samples (expectorated and induced), were collected from each patient and taken to the laboratory where sputum Gram staining for microscopy, Ziehl Nelson staining, and GeneXpert was carried out. RESULTS A total of 51 participants were involved in the study, mean age was 46.69± 15.3 years, 60.8% were males, and 39.2% were females. A total of 45 of 102 sputum samples collected was adequate when using the Bartlett’s criteria. Sixteen (31.4%) from the expectorated samples and 29(56.9%) from the induced sputum samples and the difference was a statistically significant, p-value= 0.001. Positive GeneXpert result was higher following sputum induction 14(27.5%), vs sputum expectoration 3(5.9%), and this was statistically significant, p-value=0.004. CONCLUSION There was a significant difference in diagnostic yield of tuberculosis using induced sputum compared to expectorated sputum.