Untangling Gordian knots: improving tuberculosis control through the development of 'programme theories'.

We argue that if the lessons from tuberculosis control programmes are to be drawn effectively then a more nuanced understanding is needed that takes account of the complex health system environment within which they sit. We suggest that a conceptual framework that draws upon the World Health Organization's DOTS strategy can be harnessed to assist the systematic analysis of programmes in a way that links this vertical, disease specific strategy to horizontal health system factors so that comparisons can be made. This multi-disciplinary, multi-method approach to the evaluation builds upon the work of others including Pawson and Tilley and their 'programmes theories'. This work has informed the application of an evaluation toolkit which has been successfully applied in a number of settings and assisted in the sustainable implementation of a DOTS strategy in Russia.