Economic Evaluation

To perform the calculations, the costs related to the monthly expenses of each health unit directly associated with the activities necessary for the laboratory diagnosis of DR-TB were used, considering five cost components: equipment, human resources, supplies, infrastructure, and others (maintenance and loss of damage or misuse). The direct cost of DST-MGIT and Xpert was calculated to assess its impact on the UHS routine, through detailed cost chain modeling. This resulted in the measurement of the values of the following items: equipment (acquisition of equipment, considering the amortization of capital expenditure), human resources (salaries of human resources [source: UHS/Ministry of Planning, Development and Management - MPDG] dedicated to the production process related to the diagnostic approach to resistant TB or time spent in the activity and, in the case of non-exclusive dedication, to estimate the professional’s remuneration), inputs (quantity of material to carry out consumption tests per year). Of the indirect costs, infrastructure (need to adapt the physical area, air-conditioned environment, electrical and third-party equipment, water, electricity, energy, and security) corresponded to the percentage spent on each item carried out by the set of activities involving TB in each health unit. The cost calculations of the new Xpert technology, since equipment and cartridges were not purchased at market price, considered the values “with subsidy” and “without subsidy” from the Foundation for Innovative New Diagnostics (FIND) 10 . The technique known as “mean cost” was the sum of the monthly expenses of all items used in the exam, divided by the number of exams performed in a month 13 .

For the cost-effectiveness analysis, a comparison of the two diagnostic strategies DST-MGIT versus Xpert for DR-TB was performed, considering the effectiveness of negative culture or clinical improvement in the sixth month of follow-up.

To assess the impact of variations in both effectiveness and cost components, in the sensitivity analysis, we consider the confidence interval (IC 95%) presented in the change of the initial conduct and the variation of -50% to + 25% in the final value of the cost in each technology on the incremental cost-effectiveness ratio (ICER). ICER was defined as the result of the division between the difference in cost of new technologies and the difference in their effect [ICER = (C₁ - C₂)/(E₁ - E₂)]. where C1 = alternative cost A, C2 = alternative cost B, E1 = effectiveness A, and E2 = effectiveness B 14 .

The proportion of discount used was 5%, according to the recommendations of the Methodological Guidelines for Studies of Economic Evaluation of Technologies for the Ministry of Health 14 .

The incremental cost of Xpert was calculated in two different scenarios: the first considering the value of equipment and cartridges at market prices (without subsidy), and the second with values subsidized by FIND/Diagnostic.

The inflation corrections in the country of origin and importing country were calculated according to the exchange rate variation of the commercial dollar in the period from 2012 to 2020, considering the inflation history for both countries (USA and Brazil) of the software reference for converting historical currencies and exchange rates, FXtop 15 .