Performance of a novel algorithm using automated digital microscopy for diagnosing tuberculosis

dc.contributor.authorIsmail, Nazir Ahmed
dc.contributor.authorOmar, Shaheed Vally
dc.contributor.authorLewis, James J.
dc.contributor.authorDowdy, David W.
dc.contributor.authorDreyer, Andries W.
dc.contributor.authorVan der Meulen, Hermina
dc.contributor.authorNconjana, George
dc.contributor.authorClark, David A.
dc.contributor.authorChurchyard, Gavin J.
dc.date.accessioned2015-08-21T10:28:10Z
dc.date.available2015-08-21T10:28:10Z
dc.date.issued2015-06
dc.description.abstractRATIONALE : TBDx automated microscopy is a novel technology that processes digital microscopic images to identify acid-fast bacilli (AFB). Use of TBDx as part of a diagnostic algorithm could improve the diagnosis of tuberculosis (TB), but its performance characteristics have not yet been formally tested. OBJECTIVES : To evaluate the performance of the TBDx automated microscopy system in algorithms for diagnosis of TB. METHODS : Prospective samples from patients with presumed TB were processed in parallel with conventional smear microscopy, TBDx microscopy, and liquid culture. All TBDx-positive specimens were also tested with the Xpert MTB/RIF (GXP) assay. We evaluated the sensitivity and specificity of two algorithms-(1) TBDx-GXP (TBDx with positive specimens tested by Xpert MTB/RIF) and (2) TBDx alone-against the gold standard liquid media culture. MEASUREMENTS AND MAIN RESULTS : Of 1,210 samples, 1,009 were eligible for evaluation, of which 109 were culture positive for Mycobacterium tuberculosis. The TBDx system identified 70 specimens (68 culture positive) as having 10 or more putative AFB (high positive) and 207 (19 culture positive) as having 1-9 putative AFB (low positive). An algorithm in which "low-positive" results on TBDx were confirmed by GXP had 78% sensitivity (85 of 109) and 99.8% specificity (889 of 900), requiring 21% (207 of 1,009) specimens to be processed by GXP. As a stand-alone test, a "high-positive" result on TBDx had 62% sensitivity and 99.7% specificity. CONCLUSIONS : TBDx used in diagnostic algorithms with GXP provided reasonable sensitivity and high specificity for active TB while dramatically reducing the number GXP tests performed. As a stand-alone microscopy system, its performance was equivalent to that of a highly experienced TB microscopist.en_ZA
dc.description.embargo2016-06-30en_ZA
dc.description.librarianhb2015en_ZA
dc.description.urihttp://www.atsjournals.org/journal/ajrccmen_ZA
dc.identifier.citationIsmail, NA, Omar, SV, Lewis, JJ, Dowdy, DW, Dreyer, AW, Van der Meulen, H, Nconjana, G, Clark, DA & Churchyard, GJ 2015, 'Performance of a novel algorithm using automated digital microscopy for diagnosing tuberculosis', American Journal of Respiratory and Critical Care Medicine, vol. 191, no. 12, pp. 1443-1449.en_ZA
dc.identifier.issn1073-449X (print)
dc.identifier.issn1535-4970 (online)
dc.identifier.other10.1164/rccm.201502-0390OC
dc.identifier.urihttp://hdl.handle.net/2263/49432
dc.language.isoenen_ZA
dc.publisherAmerican Thoracic Societyen_ZA
dc.rights© 2015 American Thoracic Society.en_ZA
dc.subjectTBDxen_ZA
dc.subjectXperten_ZA
dc.subjectMicroscopyen_ZA
dc.subjectTriageen_ZA
dc.subjectTuberculosis (TB)en_ZA
dc.subjectAcid-fast bacilli (AFB)en_ZA
dc.titlePerformance of a novel algorithm using automated digital microscopy for diagnosing tuberculosisen_ZA
dc.typePostprint Articleen_ZA

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