In terms of TB control, adherence to treatment may be defined as the extent to which the patient's history of therapeutic drug-taking coincides with the prescribed treatment (7).

Adherence may be measured using either process-oriented or outcome-oriented definitions. Outcome-oriented definitions use the end-result of treatment, e.g. cure rate, as an indicator of success. Process-oriented indicators make use of intermediate variables such as appointment-keeping or pill counts to measure adherence (7). The extent to which these intermediate outcomes correlate with the actual quantities of prescribed drugs taken is unknown (8).

The point that separates "adherence" from "nonadherence" would be defined as that in the natural history of the disease making the desired therapeutic outcome likely (adherence) or unlikely (nonadherence) to be achieved. There is as yet no empirical rationale for a definition of nonadherence in the management of TB. Therefore, the definition of adherence to TB treatment needs to be translated into an empirical method of monitoring both the quantity and timing of the medication taken by the patient (9). At the individual level this is desirable, but at the population level a more pragmatic approach is needed. Thus, the success of treatment, that is, the sum of the patients who are cured and those who have completed treatment under the directly observed therapy, short course (DOTS) strategy, is a pragmatic, albeit a proxy, indicator of treatment adherence.