Assessment <strong>of</strong> diagnostic <strong>and</strong> prognostic accuracyResults <strong>of</strong> the <strong>review</strong>sThis section presents the results <strong>of</strong> the following systematic <strong>review</strong>s separately:1. the diagnostic accuracy <strong>of</strong> biomarkers measured at presentation, including troponin, compared withthe universal definition <strong>of</strong> MI, <strong>and</strong> the prognostic accuracy <strong>of</strong> biomarkers, excluding troponin, forpredicting MACEs, in unselected patients presenting with chest pain <strong>and</strong> suspected ACS (see Studiesincluded in the biochemical markers <strong>review</strong>, below)2. the diagnostic accuracy <strong>and</strong> prognostic performance <strong>of</strong> exercise ECG <strong>and</strong> CTCA compared withICA for identifying CAD or predicting MACEs in unselected patients presenting with chest pain <strong>and</strong>suspected ACS (see Studies included in the computed tomographic coronary angiography <strong>and</strong> exerciseelectrocardiography <strong>review</strong>, below).Studies included in the biochemical markers <strong>review</strong>Overall, the literature searches identified 2865 citations. A flow chart describing the process <strong>of</strong> identifyingrelevant literature can be found in Figure 2. Of the titles <strong>and</strong> abstracts screened, 182 relevant fullpapers were retrieved <strong>and</strong> assessed in detail. Studies excluded from the <strong>review</strong>, with reasons, are listedin Appendix 3. A total <strong>of</strong> 88 papers evaluating the diagnostic accuracy or prognostic performance <strong>of</strong>biochemical markers met the inclusion criteria. Of these, we were unable to extract appropriate data fromseven studies 36–42 <strong>and</strong> identified three 43–45 in which there seemed to be duplication <strong>of</strong> data with otherincluded studies. A total <strong>of</strong> 40 studies reported data on diagnostic accuracy <strong>and</strong> 44 studies reported dataon prognostic performance, with six <strong>of</strong> these studies reporting both prognostic <strong>and</strong> diagnostic data. 46–51Overview <strong>of</strong> biomarker studies included in the diagnostic <strong>review</strong>Table 2 lists all the studies included in the diagnostic accuracy <strong>review</strong> <strong>and</strong> 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 <strong>of</strong> diagnostic studies <strong>of</strong> presentation troponinWe identified 21 diagnostic studies 19,20,48–50,52–57,59,62–64,66,70,72,74,77,81 <strong>of</strong> presentation TnI <strong>and</strong> 11studies 19,46,58,60,62,67,71,73,76,78,82 <strong>of</strong> TnT for inclusion in the <strong>review</strong>. Two studies 19,62 evaluated TnI <strong>and</strong> T. Thecharacteristics <strong>of</strong> the study populations are outlined in Tables 3 <strong>and</strong> 4, whereas details <strong>of</strong> the index <strong>and</strong>reference st<strong>and</strong>ard test definitions are provided in Tables 5 <strong>and</strong> 6. Some studies evaluated more than oneassay, so assays are reported separately in Tables 3 <strong>and</strong> 4. Reporting <strong>of</strong> inclusion <strong>and</strong> exclusion criteria werevariable <strong>and</strong> several studies excluded patients with a diagnostic ECG. Prevalence <strong>of</strong> MI varied from 5% to73% <strong>and</strong> 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 <strong>of</strong> variation (CV) <strong>and</strong> limit<strong>of</strong> detection (LoD). In accordance with our inclusion criteria, all studies used the universal definition <strong>of</strong> MIas the reference st<strong>and</strong>ard, <strong>and</strong> most reported using some form <strong>of</strong> adjudication, taking into account theresults <strong>of</strong> troponin testing. In most cases the troponin used for the reference st<strong>and</strong>ard was a st<strong>and</strong>ard(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 <strong>of</strong> a reference st<strong>and</strong>ard based on high-sensitivity TnT (HsTnT)alongside a reference st<strong>and</strong>ard based on the st<strong>and</strong>ard assay. For this study we extracted data based on thest<strong>and</strong>ard assay reference st<strong>and</strong>ard.Quality assessments <strong>of</strong> diagnostic studies <strong>of</strong> presentation troponinFigures 3 <strong>and</strong> 4 show the quality assessments for studies <strong>of</strong> TnI <strong>and</strong> TnT, respectively, whereas Figures 5<strong>and</strong> 6 show the methodological quality summaries. The studies were generally high quality, perhapsreflecting exclusion <strong>of</strong> lower-quality studies by our selection criteria. Presentation troponin measurementis obviously not independent <strong>of</strong> a troponin-based reference st<strong>and</strong>ard, so our assessment <strong>of</strong> verification16NIHR Journals Library
DOI: 10.3310/hta17010 Health Technology Assessment 2013 Vol. 17 No. 1Unique citations retrieved by search <strong>of</strong>electronic databases(n = 2865)Citations from reference lists <strong>of</strong>included studies <strong>and</strong> topic experts,including those published aftersearches were complete a(n = 8)Abstracts excluded after screening <strong>of</strong>titles <strong>and</strong> abstracts(n = 2683)Abstracts potentially relevant for dataextraction, full paper acquired(n = 182)Papers satisfying inclusion criteria(n = 88)Excluded studies not relevant for dataextraction for diagnosis or prognosis(n = 94)Different or unclear referencest<strong>and</strong>ard <strong>and</strong> no prognostic data(n = 61)Prognosis studies including Tn <strong>and</strong>/orCK-MB only(n = 18)Wrong outcome (n = 5)Unclear timing <strong>of</strong> tests (n = 4)Unavailable (n = 4)Less than 80% received referencest<strong>and</strong>ard (n = 1)Polish only (n = 1)Papers excluded from diagnostic<strong>analysis</strong> because data could not beanalysed (n = 7)Duplicate publications (n = 3)Diagnosis studies(n = 40)Studies used in analyses, bybiomarker:Troponin (early), n = 30H-FABP, n = 17MYO, n = 13IMA, n = 4Others, n = 10Data from some studies have beenused for more than one biomarkerPrognosis studies <strong>of</strong>biomarkers other thanCK-MB <strong>and</strong> troponin(n = 44 b )FIGURE 2 Preferred Reporting Items for <strong>Systematic</strong> Reviews <strong>and</strong> Meta-Analyses (PRISMA) flow chart biochemicalmarkers <strong>review</strong>. a, we would like to thank Pr<strong>of</strong>essor Paul Collinson <strong>and</strong> Rick Body for these studies; b, n = 6 studiesreport usable diagnostic <strong>and</strong> prognostic data for the same cohort.bias focused on whether or not the index <strong>and</strong> reference st<strong>and</strong>ard troponin were measured on differentsamples. There was some uncertainty about whether index <strong>and</strong> reference st<strong>and</strong>ard tests were assessedblind. This is not likely to have influenced reporting <strong>of</strong> the index test as in most cases this was amechanised process producing a quantitative result. However, bias could have resulted if referencest<strong>and</strong>ard adjudicators were aware <strong>of</strong> the presentation troponin result (detection bias). The only otherpossible issue was the timing <strong>of</strong> the reference st<strong>and</strong>ard, which was not always explicit.© Queen’s Printer <strong>and</strong> Controller <strong>of</strong> HMSO 2013. This work was produced by Goodacre et al. under the terms <strong>of</strong> a commissioning contract issued by the Secretary <strong>of</strong> Statefor Health. This issue may be freely reproduced for the purposes <strong>of</strong> private research <strong>and</strong> study <strong>and</strong> extracts (or indeed, the full report) may be included in pr<strong>of</strong>essional journalsprovided that suitable acknowledgement is made <strong>and</strong> the reproduction is not associated with any form <strong>of</strong> advertising. Applications for commercial reproduction should beaddressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials <strong>and</strong> Studies Coordinating Centre, Alpha House, University <strong>of</strong> Southampton SciencePark, Southampton SO16 7NS, UK.17