Risk factors for recurrent tuberculosis in England and Wales, 1998-2005

Background Information on recurrent tuberculosis can provide an indication of the effectiveness of tuberculosis services and identify patients who are most vulnerable. The objective of this study was to estimate the incidence of, and investigate risk factors for, recurrent episodes of tuberculosis in England and Wales. Methods Episodes of recurrent tuberculosis were identified among prospectively collected records of tuberculosis cases reported to the Health Protection Agency between 1998 and 2005. An episode of recurrent tuberculosis was defined as a re-notified case in the same patient after at least 12 months from the date of the initial notification. To estimate incidence, follow-up time was calculated for all cases until renotification or censure. Multivariable Cox proportionate hazard models were used to determine hazard ratios (HR) for recurrence of tuberculosis and investigate the risk associated with clinical, demographic and microbiological factors. Results Five hundred and eighty-eight recurrent tuberculosis events were identified among 53 214 cases reported between 1998 and 2005, a rate of 4.1 (95% CI 3.8 to 4.5) episodes per 1000 person years of follow-up. Factors independently associated with a greater risk of recurrent tuberculosis were HIV co-infection (HR 1.64, 95% CI 1.13 to 2.38) and belonging to a South Asian ethnic group (HR 1.54, 95% CI 1.23 to 1.93). Conclusion Tuberculosis recurrence is uncommon in England and Wales despite the absence of a universal directly observed treatment policy. The identification of HIV co-infection as a risk factor for recurrent tuberculosis is consistent with findings elsewhere. The higher risk among South Asians, however, requires further investigation.