Sample size (N) was determined by using a precision formula N=Z2p(1-p)/e2,

whereby Z is Standard Normal Deviation of 1.96 corresponding to 95% Confidence Interval, P is Population prevalence of 16.7% from a Descriptive Cross Sectional study titled Diabetes is a risk factor for pulmonary tuberculosis, a case control study from Mwanza Tanzania, and e is Precision set at 5% (0.05).

The required minimum sample size of 213 was obtained from the above estimation and the final sample size was determined to be 234 TB patients after additional of 10% for non-response rate.