A Cluster Randomised Trial to Assess the Impact of an Enhanced Case Finding Strategy on Tuberculosis Notification in The Gambia

TB is a chronic, transmissible disease, albeit with effective and curative combination therapeutic regimens available. However insufficient case detection, delayed diagnosis of TB , which prolong the duration of potential transmission, and co prevalent HIV/AIDS are the major factors responsible for increasing TB incidence. The DOTs strategy, which relies on a process of passive TB case finding, has helped to control TB in many parts of the world. Currently, the World Health Organisation's Stop TB DOTS policy is being questioned as countries that have reached and maintained targets of 70% case detection and 85% cure rates are unable to demonstrate a decline in number of cases notified.

Studies in Southern Africa suggest that if the investigators want to prevent TB in HIV-infected and uninfected people a major focus should be on decreasing transmission from people who are HIV-negative that may transmit TB for a long time on account of delayed diagnosis 5, 6. Data from studies in Ethiopia, Peru, Brazil, and Zimbabwe show different strategies of intensified or active case finding (ICF or ACF) yield significantly more TB cases than the standard of care-passive case finding.7-10 In the Zimbabwe study, point prevalence of TB declined significantly over 2 time points and was attributed to the ICF intervention. Since effective treatment for TB renders patients non-infectious within 2-4 weeks, it is likely that earlier diagnosis and initiation of treatment will ultimately reduce the incidence of TB by interrupting TB transmission. However the quantitative effect of enhanced case finding (ECF) on TB case notification rates, TB transmission, prevalence and incidence remains largely unproven.

Although there is now data from Zimbabwe regarding the impact of untargeted active case finding strategies, it is unclear how each case finding strategy compares to the standard passive case finding and the investigators are currently unable to address the cost effectiveness or otherwise of active case finding strategies in high TB burden settings with low HIV prevalence which is the scenario in most West African countries including The Gambia. Consequently, there is insufficient data to support a policy change and an urgent need for evidence to drive the necessary review of policy.

The hypothesis is a cluster randomized trial of an enhanced case finding (ECF) strategy will increase TB case notifications in The Gambia and reduce TB burden in the study area in a cost effective manner. The impact of ECF on community and household transmission of TB will also be assessed. The investigators hope this trial will contribute to this evidence base. The timing alongside a nationwide TB prevalence survey is particularly of benefit as that would provide a baseline for disease burden against which the investigators may be able to compare case notification or case detection in selected clusters.