Systematic review, meta-analysis and economic modelling of ...

Assessment of diagnostic and prognostic accuracyResults of the reviewsThis section presents the results of the following systematic reviews separately:1. the diagnostic accuracy of biomarkers measured at presentation, including troponin, compared withthe universal definition of MI, and the prognostic accuracy of biomarkers, excluding troponin, forpredicting MACEs, in unselected patients presenting with chest pain and suspected ACS (see Studiesincluded in the biochemical markers review, below)2. the diagnostic accuracy and prognostic performance of exercise ECG and CTCA compared withICA for identifying CAD or predicting MACEs in unselected patients presenting with chest pain andsuspected ACS (see Studies included in the computed tomographic coronary angiography and exerciseelectrocardiography review, below).Studies included in the biochemical markers reviewOverall, the literature searches identified 2865 citations. A flow chart describing the process of identifyingrelevant literature can be found in Figure 2. Of the titles and abstracts screened, 182 relevant fullpapers were retrieved and assessed in detail. Studies excluded from the review, with reasons, are listedin Appendix 3. A total of 88 papers evaluating the diagnostic accuracy or prognostic performance ofbiochemical markers met the inclusion criteria. Of these, we were unable to extract appropriate data fromseven studies 36–42 and identified three 43–45 in which there seemed to be duplication of data with otherincluded studies. A total of 40 studies reported data on diagnostic accuracy and 44 studies reported dataon prognostic performance, with six of these studies reporting both prognostic and diagnostic data. 46–51Overview of biomarker studies included in the diagnostic reviewTable 2 lists all the studies included in the diagnostic accuracy review and the biomarkers that wereevaluated with extractable data. We were not able to extract data for all the biomarkers reported in eachstudy. Table 2 lists only the biomarkers with extractable data.Description of diagnostic studies of presentation troponinWe identified 21 diagnostic studies 19,20,48–50,52–57,59,62–64,66,70,72,74,77,81 of presentation TnI and 11studies 19,46,58,60,62,67,71,73,76,78,82 of TnT for inclusion in the review. Two studies 19,62 evaluated TnI and T. Thecharacteristics of the study populations are outlined in Tables 3 and 4, whereas details of the index andreference standard test definitions are provided in Tables 5 and 6. Some studies evaluated more than oneassay, so assays are reported separately in Tables 3 and 4. Reporting of inclusion and exclusion criteria werevariable and several studies excluded patients with a diagnostic ECG. Prevalence of MI varied from 5% to73% and was relatively high, suggesting that patient cohorts may have been subject to implicit selectionprocesses. Time delay from symptoms to presentation varied from 1.2 hours (mean) to 6 hours (median).Several studies reported data using different diagnostic thresholds for the index test. Where this was donewe extracted data for threshold based on the 99th percentile, 10% coefficient of variation (CV) and limitof detection (LoD). In accordance with our inclusion criteria, all studies used the universal definition of MIas the reference standard, and most reported using some form of adjudication, taking into account theresults of troponin testing. In most cases the troponin used for the reference standard was a standard(i.e. not high sensitivity) assay using the 10% CV or 99th percentile as a diagnostic threshold. However,the study by Christ et al. 60 reported the use of a reference standard based on high-sensitivity TnT (HsTnT)alongside a reference standard based on the standard assay. For this study we extracted data based on thestandard assay reference standard.Quality assessments of diagnostic studies of presentation troponinFigures 3 and 4 show the quality assessments for studies of TnI and TnT, respectively, whereas Figures 5and 6 show the methodological quality summaries. The studies were generally high quality, perhapsreflecting exclusion of lower-quality studies by our selection criteria. Presentation troponin measurementis obviously not independent of a troponin-based reference standard, so our assessment of verification16NIHR Journals Library