Factors influencing sputum smear conversion at one and two months of tuberculosis treatment

In the era of Direct Observation Treatment (DOT) for tuberculosis, clinicians need to focus on high-risk groups. We present sputum conversion rate at one and two months following DOT and its predictors in Oman.

Hospital-based clinical intervention type of case series.

Chest physicians in a referral hospital examined sputum-positive cases of tuberculosis between 2001 and 2006. Patients with HIV infection and treated in the past were excluded. History of smoking, diabetes and duration of symptoms were noted. Sputum was tested for bacillus density. Blood was tested for platelet count and blood sugar levels. One and two months following treatment, the sputum was retested to determine sputum conversion. Regression analysis was done to identify the predictor of late conversion.

Of the 112 sputum-positive TB cases, 39 (34.8%) and 49 (43.7%) cases were sputum negative one and two months respectively after DOT. Lower platelet count was significantly associated with early sputum conversion. (Diff of mean = 38.3 cells x 9/L (95% CI 36.9 - 39.7). On univariate analysis, duration of symptoms, history of diabetes, smoking and ESR were not associated with the early sputum conversion. Knowledge of platelet count seems to assist the clinician to predict the early sputum conversion following DOT for pulmonary TB.

Sputum conversion rate among tuberculosis patients treated with DOT for one and two months in Oman was 34.8% and 78.6% respectively. Platelet count could assist in predicting early sputum conversion.