How do we measure adherence to anti-tuberculosis treatment?

INTRODUCTION: Completion of anti-tuberculosis (TB) treatment is of paramount importance for TB patients, as well as for the global efforts of TB control. However, there is neither a gold-standard measure to monitor adherence to TB treatment nor a widely used definition for different levels of adherence. Areas covered: in this review we aim to describe the different methods used to measure patients' adherence to anti-TB treatment, identifying their main strengths and limitations, with a focus on low resource settings. Expert commentary: there is a need for continuing the quest for a low cost, reliable and acceptable measure of adherence to TB treatment. We should harmonize treatment adherence measurement to allow adequate comparison of different interventions aimed at increasing adherence to TB treatment, although the way we ensure adherence can affect adherence endpoints themselves. The accuracy of adherence measurement is of importance in the context of drug clinical development.