Defaulting on treatment – where are we?
Default from treatment for drug resistant TB (DR-TB), (now classified as lost to follow-up), defined as interruption of TB treatment for two or more consecutive months, is a problem that is reported by TB control programmes globally. Completion of treatment for DR-TB is particularly difficult since treatment duration is long (at least 18 months), involves a large number of pills, and a painful injectable agent in treatment regimens characterised by significant side effects. Default from treatment impacts on attainment of treatment success (cure and treatment completion) and is associated with high mortality post treatment. Furthermore these patients continue to contribute to community transmission of DR-TB. This major driver of the epidemic since they may stop treatment before sputum conversion or revert back to infectiousness given their incomplete treatment status.
Nationally the default rate was estimated at about 18% over the period 2007-2010. However, high rates have been consistently reported in various settings across the country. Between 1992 and 2002 the default proportion peaked at 40% in the West Coast Winelands, with a recent analysis in the same area reporting a 27% default rate. Analysis of outcomes of DR-TB patients in eight provinces (excluding the Western Cape Province), between 2000 and 2004, and a study among DR-TB patients in KwaZulu-Natal (2000-2003), both found a 21% default rate. Recent data from a study in KwaZulu-Natal reported a 14% default rate at four sites in the province. In a decentralised community based DR-TB programme, in Khayelitsha, Cape Town, default from treatment over the period 2007 to 2011 was 31%. This higher rate of default in Khayelitsha (compared to KZN and recent data from the Winelands) is probably due to treatment of patients who are clinically less ill (since treatment can be initiated earlier in the decentralised community based programme), and would therefore be more likely to default when compared to sicker patients seen where treatment is more centralised.
Studies have shown that default from DR-TB treatment is driven both directly and indirectly by interplay of individual, socio-demographic, economic, clinical and programmatic factors. Amongst the myriad of risk factors known to be associated with default from DR-TB treatment, in South Africa, young age, being male, poor health-care worker attitudes, residing in the Eastern Cape or Western Cape provinces, alcohol and substance abuse, previous treatment for DR-TB, and economic instability have been identified as risk factors for default in various settings. Analysis of data from Khayelitsha has also shown that default occurs early in treatment and persists throughout the treatment period.
A recent systematic review noted that current interventions for supporting patients on DR-TB treatment are poorly described and are based on weak evidence, a finding consistent with the high levels of default seen in South Africa. Lower default rates were associated with engagement of community health workers as Directly Observed Treatment (DOT) supporters, provision of DOT throughout treatment, provision of patient education, and small cohort sizes (<100). The review rightly advocates for sound research into these relatively low cost and promising strategies to address the challenge of poor retention of patients on treatment for the required period3. With exception of small cohort sizes, these strategies could easily be integrated into current health practice in South Africa, given the already existing infrastructure of community health workers. Ongoing monitoring and support of health facilities is also crucial. Occurrence of default throughout treatment highlights the need for early initiation and support for patients throughout treatment. Strategies to identify and support patients as early as possible after they interrupt treatment – prior to meeting the definition of default at two months off treatment – may further improve retention in care.
While more effective treatment retention strategies are vital in reducing default from DR-TB treatment, it is undeniable that shorter and less toxic treatment regimes that exclude the painful injectable agent are critical in addressing this problem and the DR-TB problem as a whole. Therefore efforts to reduce default should also be directed at improving treatment regimens.
Moyo and Cox are with Médecins Sans Frontières in Khayelitsha, Cape Town.