Impact of policy and practice on the effectiveness of contact screening for tuberculosis

Screening for tuberculosis is conducted because TB is a disease of public health importance that can be prevented if screening is followed by isoniazid prophylaxis for infected individuals. Screening alone is not effective unless that screening is rational and systematic and is followed by prevention where appropriate. Our aim was to consider whether the TB contact screening guidelines are evidence-based and appropriate, how well these guidelines are implemented, and how policy and practice impact on prevention.

A cohort of 1,142 recent contacts screened in 1991 in Victoria, Australia, was studied. We evaluated the appropriateness of the screening guidelines and how well they were implemented and how the combination of these two factors impacted on the efficacy of the screening program.

The screening guidelines required updating and were not evidence-based. Chest radiograph (CXR) was overused and was the sole screening tool for nearly 40% (449/1,142) of contacts. Eighty percent of repeat CXRs were done following a normal initial study. Skin testing was underused. In nearly 60% (658/1,142) of all contacts, the presence or absence of infection could not be determined because a skin test was not done and the CXR, if done, was clear. Only 22% (38/175) of identified, eligible contacts received isoniazid preventive therapy.

Lack of evidence-based guidelines, as well as poor adherence to guidelines, resulted in an inefficient program. This problem may not be unique to the study setting, but cannot be identified without systematic program evaluation, for which we have provided a model.