Risk factors for drug resistant tuberculosis in Leicestershire--poor adherence to treatment remains an important cause of resistance.

In the light of rising numbers of tuberculosis (TB) cases in the United Kingdom, the problem of anti-tubercular drug resistance remains a significant concern. Drug resistant TB cases are more difficult and costly to treat, and require appropriate treatment and control mechanisms. This matched case control study aimed to investigate risk factors for resistance in Leicestershire, using data for laboratory isolates of Mycobacterium tuberculosis identified from 1993 to 1998. Each case, defined as culture positive laboratory isolates resistant to at least one first-line drug, was matched to four fully sensitive controls on age, sex and ethnic group. Twenty-three cases and 81 controls were included in the analysis. Drug resistance in Leicestershire was found to be associated with poor adherence to treatment (OR 4.8, 95% CI 1.6-14.4, P=0.005) and with previous TB (OR 3.7, 95% CI 1.2-11.8, P=0.022). These findings emphasize the need to provide support to patients taking treatment in order to maximize adherence.