Impact of GeneXpert MTB/RIF® on Patients and Tuberculosis Programs in a Low-Burden Setting: A Hypothetical Trial
Davis JL1, Kawamura LM, Chaisson LH, Grinsdale J, Benhammou J, Ho C, Babst A, Banouvong H, Metcalfe JZ, Pandori M, Hopewell PC, Cattamanchi A.
Am J Respir Crit Care Med. 2014 May 28.
Rationale: Guidelines recommend routine nucleic-acid amplification testing (NAAT) in patients with presumed tuberculosis (TB), but these tests have not been widely adopted. GeneXpert MTB/RIF (Xpert), a novel, semi-automated TB NAAT with enhanced operational characteristics, has renewed interest in this technology, but data from low-burden countries are limited. Objective: We sought to estimate Xpert's potential clinical and public health impact on empiric treatment, contact investigation, and housing in patients undergoing TB evaluation. Methods: We performed a prospective, cross-sectional study with two-month follow-up comparing Xpert with standard strategies for evaluating outpatients for active pulmonary TB at the San Francisco Department of Public Health TB Clinic between May 2010 and June 2011. We determined the diagnostic accuracy of standard empiric TB treatment, contact investigation, and housing algorithms in reference to Mycobacterium tuberculosis culture and compared them with a single Xpert test. We estimated the potential incremental value of Xpert in diagnosing individuals correctly, and reductions in unnecessary treatment, contact investigation, and housing. Measurements & Main Results: 156 patients underwent Xpert testing. Fifty-nine (38%) received empiric TB treatment. Thirteen (8%) had culture-positive TB. Xpert-guided management would have decreased over-treatment by 94%, eliminating a median of 44 over-treatment days (interquartile range 43-47) per patient and 2169 total over-treatment days (95%CI 1938-2400) for the program annually, without reducing early detection of TB patients. We observed similar benefits for contact investigation and housing. Conclusions: Xpert-guided decisions could greatly reduce the frequency and impact of unnecessary initial treatment, contact investigation, and housing, providing substantial patient and programmatic benefits.