SPUTUM SMEAR CONVERSION IN PULMONARY TUBERCULOSIS

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Department of Medicine

ABSTRACT
Tuberculosis (TB) is a high burden global problem. Nigeria ranks fifth among the 22 high burden TB countries globally and first in Africa. Directly observed treatment shortcourse (DOTS) is central to all TB control programs. One indicator of assessing the effectiveness of DOTS is through sputum smear conversion rates at the end of intensive phase. Whether some of the patients become smear negative early during the intensive phase has not been investigated. There is lack of data to clarify this research question. The rate and time to sputum smear conversion were determined as well as the relationship between baseline sputum smear grades and time to sputum smear conversion described. A longitudinal study at National Tuberculosis and Leprosy Training Center, (NTBLTC) Zaria was employed from January-June 2010. Data collection was by laboratory method using Ziehl Neelsen staining technique for grading the bacillary load in the sputum at diagnosis and weekly follow-up specimens. HIV status of each patient was determined and 2007-2009 records analyzed. Data was entered and analyzed by Epi-Info version 3.5.1 Of the 62 patients analyzed, 67.7% were males with male/female ratio of 2:1. The productive age group constituted 88.7% of those affected with median age of 32 years. About 75.8% were HIV negative with TB/HIV co-infection of 24.2%; 79% were new TB patients. Overall, Zaria and her immediate neighboring LGAs had 82.3% of patients. Of the 58 patients that converted, the mean time to sputum smear conversion was 2.7 ± 1.3 weeks, standard error (SE), 0.2 (95% confidence interval 2.3-3.1). Sputum smear conversion rate peaked in week three with 71%. By the end of intensive phase, conversion rate was 93.5%. At univariate analysis, by first week, 90% of sputum smear grade of ≤ 1+ converted but none among sputum grade of 3+. Being HIV positive was not associated with early conversion at bivariate analysis with p-value of 0.31 by Fisher’s exact. Of the 611 records analyzed for 2007-2009, the average sputum conversion rate was 82%. When conversion rate was categorized by sputum grade, it was statistically significant (X2 15.5 df 4 and p-value 0.003), indicating that sputum smear grade is a strong predictor of sputum smear conversion. It was concluded that sputum smear conversion rate during the intensive phase was high and peaked early. This may offer a rethink of duration of admission policy or isolation and a reduction of routine time for assessing sputum conversion from seventh week to the fifth week at least at NTBLTC, Zaria. A national survey on sputum smear conversion is recommended in a further study for wider national application. Key words: Tuberculosis, Sputum, Conversion, intensive phase, acid fast bacilli.