Abstract
BackgroundProficiency testing (PT) is an important quality assurance measure toward ensuring accurate and reliable diagnostic test results from clinical and public health laboratories. Despite the rapid expansion of the Xpert® MTB/RIF assay for the detection of tuberculosis in resource-limited settings (RLS), low-cost PT materials for Xpert MTB/RIF external quality assessment (EQA) are not widely available.ObjectiveWe sought to determine whether a dried tube specimen (DTS)-based PT programme would be a feasible option to support Xpert MTB/RIF EQA in RLS.MethodsBetween 2013 and 2015, the United States Centers for Disease Control and Prevention developed and conducted a voluntary EQA programme using DTS-based PT material. Eight rounds of PT, each comprising five DTS samples, were provided to enrolled testing sites. After each round, participant results were compared to expected results, scored as satisfactory or unsatisfactory, and sites were provided with performance reports.ResultsProgramme enrolment increased from 102 testing sites in seven countries to 441 testing sites in 14 countries over the course of three years. In each PT round, approximately 90% of participating sites demonstrated satisfactory performance. In seven of the 14 enrolled countries, the proportion of sites with a satisfactory score increased between the first round of participation and the most recent round of participation.ConclusionThis programme demonstrated that it is possible to implement an Xpert MTB/RIF PT programme for RLS using DTS, that substantial demand for Xpert MTB/RIF PT material exists in RLS, and that country performance can improve in a DTS-based PT programme.
Highlights
The World Health Organization recommends the Xpert® MTB/RIF (Mycobacterium tuberculosis/ rifampicin) assay (Cepheid, Sunnyvale, California, United States) as one of the initial diagnostic tests for all individuals evaluated for tuberculosis.[1,2]
Mycobacteria were grown in BACTEC® MGIT 7 mL tubes (Becton, Dickinson and Company, Sparks, Maryland, United States) and inactivated using a 2:1 ratio of Xpert MTB/RIF sample reagent (Cepheid, Sunnyvale, California, United States) to MGIT culture incubated for 2 hours with intermittent vortexing
To test dried tube specimen (DTS), the DTS were rehydrated with 2.5 mL of sample reagent, shaken vigorously 20 times and incubated at room temperature for 15 minutes with additional shaking repeated after 10 min
Summary
The World Health Organization recommends the Xpert® MTB/RIF (Mycobacterium tuberculosis/ rifampicin) assay (Cepheid, Sunnyvale, California, United States) as one of the initial diagnostic tests for all individuals evaluated for tuberculosis.[1,2] The Xpert MTB/RIF assay is an integrated sputum processing and real-time polymerase chain reaction system that rapidly and simultaneously detects M. tuberculosis and the presence of mutations conferring resistance to rifampicin.[3]. Proficiency testing provides objective evidence of accurate testing and may identify areas in the diagnostic process, including pre-analytic, analytic, and post-analytic phases, where quality improvement is needed.[5,6] The rapid scale-up of Xpert MTB/RIF testing in RLS has not coincided with the same investment in quality assurance activities for the assay. Few PT providers for the Xpert MTB/RIF assay offer materials to sites in RLS, leaving a substantial gap in external quality assessment implementation that could otherwise help to confirm site competency in assay administration and accuracy of test results for limited-resource countries.[7,8,9]. Proficiency testing (PT) is an important quality assurance measure toward ensuring accurate and reliable diagnostic test results from clinical and public health laboratories. Despite the rapid expansion of the Xpert® MTB/RIF assay for the detection of tuberculosis in resource-limited settings (RLS), low-cost PT materials for Xpert MTB/RIF external quality assessment (EQA) are not widely available
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