The cost-effectiveness of evidence-based guidelines and practice for screening and prevention of tuberculosis

Introduction: The potential cost-effectiveness of screening depends on the risk of tuberculosis (TB) in the population being screened and the rate at which the screening outcome (prevention) is achieved. Aims: To compare the cost-effectiveness of contact screening for TB for: (1 ) contact screening as it actually occurred in Victoria in 1991 (Model 1); (2) the process which should have occurred had the 1991 contact screening g uidelines been followed (Model 2); (3) a hypothetical evidence-based model (Model 3). Methods: Three models were constructed according to the aims. The cost-effe ctiveness of contact screening is presented as costs to government per unit outcome (in the form of cases prevented, cases found and contacts traced) for each model. Assumptions about disease behaviour were consistent between models. A sensitivity analysis was performed to examine the effect of the assumptions made in Model 3 about rates of referral and treatment of infect ed contacts, and about the efficacy of isoniazid (INH) in preventing TB. Results: The total cost of Model 1 was greater than that of the other Model s. Model 1 is the least cost-effective, costing $309065 per case prevented, and Model 3 is the most cost-effective, costing $32210 per case prevented. The cost of Model 2 was $58742 per case prevented. The incremental cost-ef fectiveness of Model 3 compared to Model 2 is $107 per additional contact s creened, and $3881 per additional case prevented. Case finding is not as co st-effective as best-practice case prevention, ranging from $231799 per cas e found in Model 1 to $205596 per case found in Model 2. The sensitivity an alysis shows that the cost-effectiveness of Model 3 decreases with lower re ferral rates, lower rates of preventive therapy, and lower efficacy of INH. However, even allowing for reduced programme parameters, Model 3 is most c ost-effective. Discussion: Costing policy options is an important component of programme d elivery, but needs to be considered in the context of the product being pur chased, e.g. the prevention of disease, or case finding. Case finding as a product of contact screening is expensive in all three models. Prevention o f TB, on the other hand, can be cost-effective, as shown in Model 3. It was least cost-effective in Model 1, largely because prevention was not consid ered a priority, and few infected contacts actually received preventive the rapy. Clear programme aims, adherence to guidelines and high rates of preve ntive therapy are essential in order to achieve cost-effectiveness. Copyrig ht (C) 2000 John Wiley & Sons, Ltd.