Therefore, following our ROC analysis the optimal cut-off value of the hyplex® TBC PCR assay was set to an OD of 0.400 in our study. Using this corrected value, the technical specificity determined by the manufacturer would indeed rise to 100%, while diagnostic sensitivity and specificity still range within reasonable limits. LEE011 The hyplex® TBC offers an overall sensitivity of 83.1% and a specificity of 99.25%, when compared to culture results as standard reference. The overall sensitivity of 83.1% was similar to that found for other NAAT assays which tested respiratory and non-respiratory specimens (range: 61.8% to 93.5%; median:
83.5%) [7–10, 12–16, 18, 19]. In contrast to some other studies which found significantly reduced sensitivities for non-respiratory specimens with various NAATs [7, 10, 14], the hyplex® TBC assay even showed a higher sensitivity for non-respiratory samples (91.6% for non-respiratory versus 84.2% for respiratory RAD001 cell line samples). Resolving against smear-negative
specimens, the sensitivity of the hyplex® TBC test was rather in the lower range (45.1%) when compared to other NAAT assays (range: 46% to 75,3%, median: 56%) [8, 9, 11–13, 15, 18–20]. Resolving against smear-positive specimens only, the sensitivity of the hyplex® TBC test (93,4%) was in accordance with other NAAT assays (range: 91,7% to 100%; median: 96,2%) [8, 11, 13–15, 18, 19]. The overall specificity estimate of 99.25% for hyplex® TBC was remarkably high compared to other NAAT assays (range: 97.4% to 100%; median: 99.2%) [7–9, 11, 14–16, 18, 20] and even ranged clearly above the pooled
specificity of 97% found by meta-analysis . The positive and negative predictive values (90.4% and 98.5%) were calculated from specificity and sensitivity estimates found in this study after extrapolation to a total number of 3000 specimens per year and a prevalence of true TB positive specimens of 8%. When compared to other evaluation studies which were based on similar rates of true TB positive samples (range: 10% to 13.2%) [8, 11, 21], the PPV of 90.4% of the hyplex® TBC was in the lower third (range: 88.5% to 100%) whereas the NPV of 98.5% turned out excellent (range: 96.7% to 98.6%). In many studies, the prevalence of positive specimens in the respective setting of routine diagnostics was not GDC-0449 solubility dmso included in the calculation of the PPV and Ribose-5-phosphate isomerase NPV. This resulted mostly in an overestimation of the significance of the values. Additionally, the values are influenced by factors like the selection of specimens. For these reasons, the comparison of PPV and NPV with former studies and other assays is rather difficult. Only two non-TB samples were finally classified as false-positive. In one of them grew M. intracellulare. It is unlikely that the positive PCR resulted from a dual infection of the patient with M. intracellulare and MTB. Furthermore, the absence of MTB DNA in this specimen was assessed by CTM PCR.