Evaluation of Sputum Decontamination Methods to Facilitate the Mycobacterium tuberculosis Detection in a Tertiary Care Hospital

ISSN: 2319-7706 Volume 5 Number 8 (2016) pp. 889-894 Journal homepage: http://www.ijcmas. com Tuberculosis caused by Mycobacterium tuberculosis (or Koch’s bacillus) even though curable and preventable it is still one of the leading infectious causes of morbidity and mortality especially in developing countries like India. Diagnostic methods available to detect tuberculosis are Direct approach by Microscopy, Culture, Biochemical test, Nuclear techniques. In developing countries diagnosis of acid fast bacilli is performed by microscopic examination of Ziehl-Neelsen (ZN) stained sputum smear, because it is simple, inexpensive and it provides rapid results. But this technique has a low sensitivity 22-43% for single smear. And also up to 60% sensitivity under optimal conditions, when compared with cultures so that culture remains as gold standard to diagnose tuberculosis. The threshold for detection of acid fast bacilli in sputum samples under optimal condition is between 10 4 -10 5 bacilli/ml, which can be obtained by decontamination & concentration techniques. Sputum microscopy remains the mainstay of diagnosis of pulmonary tuberculosis but lacks sensitivity compared to culture. Pre-requisite for microscopic examination of sputum sample is prior decontamination. Rationale for the study: There are only a very few studies done in South India to report that Hypertonic Saline Sodium Hydroxide (HS-SH) method of decontamination is superior to gold standard NALC-NaOH method in India. So, we would like to evaluate Hypertonic Saline Sodium Hydroxide (HS-SH) method for decontamination of sputum samples for sputum microscopy. Main objective of our study is to evaluate the performance of the Novel Hypertonic Saline Sodium hydroxide (HS-SH) method with the gold standard NALC-NaOH for decontamination of sputum specimens to detect acid fast Mycobacterium tuberculosis. Institutional Human Ethical Committee clearance and Patient’s informed written consent obtained. The Study was conducted as a prospective epidemiological study in Diagnostic Microbiology section of Central Service Laboratory for 6 months from November 11, 2015 to May 10, 2016. Total of 143 sputum samples obtained from both in-patients and out-patients of Karpagam Medical College Hospital from various departments like Medicine, Surgery, TB & RD and Orthopedics were subjected to decontamination by both HS-SH method and NALC-NAOH methods. Slides were then examined under oil immersion for acid fast bacilli by conventional Ziehl Neelsen staining microscopic method. Results: Out of 143 microbiological sputum samples, 104 were found to be positive for acid fast bacilli by both Modified petroff’s method and Hypertonic Saline Sodium Hydroxide method (HS-SH) of concentration and decontamination and 39 samples were negative by both these methods. Sensitivity, Specificity, Positive predictive value & Negative predictive value of the HS-SH method was found to be 100%. Conclusion: The HS-SH sputum decontamination method is equally sensitive, specific, cost-effective, feasible and less time consuming procedure compared to the gold standard NALC-NaOH method for decontamination of Mycobacterium tuberculosis from sputum samples and can be routinely used in all peripheral health centres because of the low cost, especially in developing countries. K e y w o r d s