Processing Sputum for Diagnosis and Monitoring Treatment in Tuberculosis Patients in Calabar, Nigeria

Abstract

The direct smear technique of sputum examination has low sensitivity. This work was aimed at using simple and affordable procedures to improve the sensitivity of the direct smear technique suspected of having tuberculosis. The samples were then digested with 5% sodium hypochlorite and concentrated by sedimentation at room temperature and centrifugation at 3000xg for 15 minutes. Smears were made from the sediments, stained with Ziehl Neelsen stain and examined at x100 magnification. Acid fast bacilli (AFB) detection rates of 17, 27 and 33% were recorded for direct smear, sedimentation and centrifugation techniques respectively. There were significant differences in detection rates between the direct smear and concentration methods (P<0.05). Concentration by sedimentation and centrifugation increased the sensitivity of the direct smear to 61.4 and 66% respectively; specificity was also increased to 97% by both concentration methods. Concentration also increased the number of AFB seen (at >10 AFB/20 fields) from 2.9% to
16.7% and 20.0% for direct smear, sedimentation and centrifugation respectively. Sputum concentration after digestion with sodium hypochlorite is recommended for detection of AFB in laboratories in developing countries where advances in the diagnosis of tuberculosis are yet lacking.