The results was read according to the grading system of the International Union Against TB and Lung Diseases as - , +, ++, +++7. Thereafter, the sputum was decontaminated using 4 per cent NaOH. The resulting solution was mixed using vortex mixer. About one ml from the mixture was inoculated onto prepared modified Ogawa egg medium as previously demonstrated8 and incubated at 37oC for six weeks. M. tuberculosis strain H37Rv and sterile Ogawa medium were used as positive and negative controls respectively. Contamination on Ogawa medium was determined by looking for growth before two weeks of incubation and by carrying out Z-N reaction and standard biochemical tests9. Subjects from whom AFB positive samples.
