Many factors that predict delay seem to be mutually associated. It is impossible to single out one factor that, regardless of other conditions, explains diagnosis delay and treatment default. Moreover, even multivariate analyses that explain TB detection and treatment adherence in one community do not provide conclusive results that are applicable to different settings. Although the literature has plenty of case studies with individual findings that can be tested, the dearth of comparative studies does not allow us to draw general conclusions.The inability of health systems to screen people before they develop active TB largely accounts for system delay. From the studies reviewed, a number of factors account for why health systems miss patients. The lack of diagnostic tools in health clinics, bad implementation, overall under-utilization of health care services, and oversight by healthcare providers (due to insufficient knowledge and neglect) are plausible explanations. This article mainly focused on directly observed treatments (DOTS) therapy for tuberculosis and related factors.