Effects and determinants of tuberculosis drug stockouts in South Africa

The frequent occurrence of medicine stockouts represents a significant obstacle to tuberculosis control in South Africa. Stockouts can lead to treatment alterations or interruptions, which can impact treatment outcomes. This study investigates the determinants and effects of TB drug stockouts and whether poorer districts are disproportionately affected.

TB stockout data, health system indicators and TB treatment outcomes at the district level were extracted from the District Health Barometer for the years 2011, 2012 and 2013. Poverty terciles were constructed using the Census 2011 data to investigate whether stockouts and poor treatment outcomes were more prevalent in more impoverished districts. Fixed-effects regressions were used to estimate the effects of TB stockouts on TB treatment outcomes.

TB stockouts occurred in all provinces but varied across provinces and years. Regression analysis showed a significant association between district per capita income and stockouts: a 10% rise in income was associated with an 8.50% decline in stockout proportions. In terms of consequences, after controlling for unobserved time invariant heterogeneity between districts, a 10% rise in TB drug stockouts was found to lower the cure rate by 2.10% (p < 0.01) and the success rate by 1.42% (p < 0.01). These effects were found to be larger in poorer districts.

The unequal spread of TB drug stockouts adds to the socioeconomic inequality in TB outcomes. Not only are stockouts more prevalent in poorer parts of South Africa, they also have a more severe impact on TB treatment outcomes in poorer districts. This suggests that efforts to cut back TB drug stockouts would not only improve TB treatment outcomes on average, they are also likely to improve equity because a disproportionate share of this burden is currently borne by the poorer districts.