Clinical impact and cost analysis of the use of either the Xpert MTB Rif test or sputum smear microscopy in the diagnosis of pulmonary tuberculosis in Rio de Janeiro, Brazil

Introduction The molecular test Xpert MTB/RIF (Xpert) has been recommended for use in the diagnosis of pulmonary tuberculosis (PTB); however, data on the cost of incorporating it under routine conditions in high-burden countries are scarce. The clinical impact and costs incurred in adopting the Xpert test in routine PTB diagnosis was evaluated in a prospective study conducted from November 2012 to November of 2013, in the City of Rio de Janeiro, Brazil. Methods The diagnostic and therapeutic cascade for TB treatment was evaluated using Xpert in the first stage (S1), and sputum smear microscopy (SSM) in the second stage (S2). The mean costs associated with each diagnostic test were calculated including equipment, human resources, supplies, and infrastructure. Results We included 232 subjects with probable TB (S1 = 87; S2 = 145). The sensitivities of Xpert and SSM were 91.7% (22/24) and 79.1% (34/43), respectively. The median time between triage and TB treatment initiation in S1 (n = 24) was 14.5 days (IQR 8-28.0) and in S2 (n = 43) it was 8 days [interquartile range (IQR) 6-12.0]. The estimated mean costs per examination in S1 and S2 were US$24.61 and US$6.98, respectively. Conclusions Compared with SSM, Xpert test showed a greater sensitivity, but it also had a time delay with respect to treatment initiation and a higher mean cost per examination.