Measuring patient compliance in the treatment of pulmonary tuberculosis in Cape Town--pitfalls in study design. 
Pulmonary tuberculosis is the greatest public health problem in Cape Town and patient non-compliance appears to be a persistent problem in its management.  A study was conducted in March 1984 to determine the proportion of known tuberculosis patients in the area under the jurisdiction of the Cape Town City Council who were not receiving adequate therapy.  A fallaciously low estimate of the problem of non-compliance occurred as a result of the use of a cross-sectional study design.  The sources of bias as well as their direction and impact on the results are discussed.  An alternative inception cohort sampling method is suggested.