Diagnostic accuracy of the Cepheid 3-gene host response fingerstick blood test in a prospective, multi-site study: interim results.
Sutherland JS., van der Spuy G., Gindeh A., Thuong NT., Namuganga AR., Owolabi O., Mayanja-Kizza H., Nsereko M., Thwaites G., Winter J., Dockrell HM., Scriba TJ., Geluk A., Corstjens P., Stanley K., Richardson T., Shaw JA., Smith B., Malherbe ST., Walzl G., TrENDx-TB consortium None.
BackgroundThe development of a fast and accurate, non-sputum-based point-of-care triage test for tuberculosis (TB) would have a major impact on combating the TB burden worldwide. A new fingerstick blood test has been developed by Cepheid (the Xpert-MTB-Host Response (HR)-Prototype), which generates a 'TB score' based on mRNA expression of 3 genes. Here we describe the first prospective findings of the MTB-HR prototype.MethodsFingerstick blood from adults presenting with symptoms compatible with TB in South Africa, The Gambia, Uganda and Vietnam was analysed using the Cepheid GeneXpert MTB-HR prototype. Accuracy of the Xpert MTB-HR cartridge was determined in relation to GeneXpert Ultra results and a composite microbiological score (GeneXpert Ultra and liquid culture) with patients classified as having TB or other respiratory diseases (ORD).ResultsWhen data from all sites (n=75 TB, 120 ORD) were analysed, the TB score discriminated between TB and ORD with an AUC of 0·94 (CI, 0·91-0·97), sensitivity of 87% (CI, 77-93%) and specificity of 94% (88-97%). When sensitivity was set at 90% for a triage test, specificity was 86% (CI, 75-97%). These results were not influenced by HIV status or geographical location. When evaluated against a composite microbiological score (n=80 TB, 111 ORD), the TB score was able to discriminate between TB and ORD with an AUC of 0·88 (CI, 0·83-0·94), 80% sensitivity (CI, 76-85%) and 94% specificity (CI, 91-96%).ConclusionsOur interim data indicate the Cepheid MTB-HR cartridge reaches the minimal target product profile for a point of care triage test for TB using fingerstick blood, regardless of geographic area or HIV infection status.