Discussionspecificity were 62% (95% predictive interval 35% to 83%) <strong>and</strong> 83% (95% predictive interval 35% to 98%),respectively. These findings suggest inadequate diagnostic accuracy to act as a single diagnostic test for MIat presentation.A few studies reported the accuracy <strong>of</strong> alternative biomarkers in combination with troponin atpresentation, with the combination being positive if either marker were positive. H-FABP, copeptin,IMA <strong>and</strong> myoglobin improved sensitivity for MI at presentation but at the expense <strong>of</strong> loss <strong>of</strong> specificity.However, the estimates <strong>of</strong> diagnostic accuracy for presentation troponin alone varied substantially inthese studies <strong>and</strong> used an unclear threshold for positivity in some cases. Our <strong>meta</strong>-<strong>analysis</strong> suggests thathigh-sensitivity troponin assays can achieve similar sensitivity to the biomarker <strong>and</strong> troponin combinationwith a similar loss <strong>of</strong> specificity. Future evaluations <strong>of</strong> alternative biomarkers at presentation should includemeasurement <strong>of</strong> a high-sensitivity troponin assay to determine whether or not the biomarker still producesan incremental improvement in sensitivity.Prognostic accuracy <strong>of</strong> biomarkers for predicting major adverse cardiac eventsThe prognostic value <strong>of</strong> troponin is well established 8 <strong>and</strong> elevated troponin levels is associated withincreased potential to benefit from treatment. 9,155 As a result, troponin is established as an essentialbiomarker in the assessment <strong>of</strong> suspected ACS. We identified a large number studies evaluating the ability<strong>of</strong> other biomarkers to predict MACEs in patients with suspected ACS. However, many <strong>of</strong> these simplyevaluated whether there was an association between biomarker levels <strong>and</strong> risk <strong>of</strong> MACEs. In clinicalassessment, the ECG <strong>and</strong> troponin are already established in routine practice on the basis <strong>of</strong> value inpredicting adverse outcome, so any new biomarker would need to demonstrate additional prognosticvalue beyond routine assessment. We found some evidence that BNP, NT-pro-BNP, MPO <strong>and</strong> H-FABPcould predict MACEs even after adjustment for troponin <strong>and</strong> other variables in multivariate <strong>analysis</strong>.However, results were sometimes inconsistent <strong>and</strong> it was not always clear whether or not all potentiallyimportant covariates had been included in <strong>analysis</strong>. We also found evidence that CRP, PAPP-A <strong>and</strong> H-FABPcould predict MACEs in troponin-negative patients. These findings were based on a small number <strong>of</strong>heterogeneous studies with differing methods <strong>of</strong> <strong>analysis</strong> <strong>and</strong> there was some inconsistency in thefindings. Meta-<strong>analysis</strong> was not possible so the estimates <strong>of</strong> RR were based on single studies <strong>and</strong> should beinterpreted with caution.Diagnostic accuracy <strong>of</strong> computed tomographic coronary angiography <strong>and</strong>exercise electrocardiography for coronary artery diseaseThe diagnostic accuracy <strong>of</strong> CTCA <strong>and</strong> exercise ECG for identifying CAD in patients with stable symptomshas been extensively studied <strong>and</strong> summarised in previous <strong>meta</strong>-analyses. We aimed to determine whetheror not similar estimates existed in patients presenting to hospital with suspected ACS.We identified eight studies comparing CTCA to conventional coronary angiography in patients presentingwith suspected ACS, reporting sensitivities ranging from 83% to 100% <strong>and</strong> specificities ranging from 54%to 100%. The summary estimates for sensitivity <strong>and</strong> specificity were 93% (95% predictive interval 61%to 99%) <strong>and</strong> 87% (95% predictive interval 16% to 100%), respectively. The studies were relatively small,evaluated various different techniques <strong>and</strong> used different methods <strong>of</strong> <strong>analysis</strong>, so there are a number <strong>of</strong>potential explanations for the variation in results. Only one study 126 used 64-slice CT <strong>and</strong> this reported thehighest sensitivity <strong>and</strong> specificity (both 100%). The other studies used 16- or 4-slice CT <strong>and</strong> reported lowersensitivity <strong>and</strong> specificity.Our findings are similar to other published <strong>review</strong>s. Mowatt et al. 25 sought all diagnostic studies <strong>of</strong> CTCA<strong>and</strong> included 18 studies with 1286 patients in the <strong>meta</strong>-<strong>analysis</strong>. Most <strong>of</strong> the included studies were <strong>of</strong>patients with stable symptoms rather than suspected ACS. Sensitivity ranged from 94% to 100%, with apooled sensitivity <strong>of</strong> 99% (95% CrI 97% to 99%). Specificity ranged from 50% to 100%, with a pooledspecificity <strong>of</strong> 89% (95% CrI 83% to 94%). Athappan et al. 167 included 16 studies <strong>of</strong> CTCA in acute chestpain. The pooled sensitivity <strong>and</strong> specificity for ACS were 0.96 (95% CI 0.93 to 0.98) <strong>and</strong> 0.92 (95% CI108NIHR Journals Library
DOI: 10.3310/hta17010 Health Technology Assessment 2013 Vol. 17 No. 10.89 to 0.94), respectively. There was surprisingly little overlap between this <strong>review</strong> <strong>and</strong> ours. The studies<strong>of</strong> Sato et al., 129 Tsai et al. 130 <strong>and</strong> Olivetti et al. 128 were included in both <strong>review</strong>s. The other five studies weidentified 123–127 were not included in the Athappan <strong>review</strong>. We excluded four studies 131,135,168,169 becauseonly those with positive CTCA underwent ICA as the reference st<strong>and</strong>ard test, two studies 170,171 because thereference st<strong>and</strong>ard was not based on ICA, <strong>and</strong> two studies 172,173 because the study population were notpatients with suspected ACS. We excluded studies that used reference st<strong>and</strong>ards other than CAD on ICA<strong>and</strong> studies that confirmed only CAD on ICA in those with a positive CTCA result because these studieswill be prone to work-up bias <strong>and</strong> will overestimate diagnostic parameters. This probably explains why ourestimates <strong>of</strong> sensitivity <strong>and</strong> specificity (albeit for CAD rather than ACS) were lower than those reported byAthappan et al. 167The most recent <strong>meta</strong>-<strong>analysis</strong> 23 <strong>of</strong> the diagnostic accuracy <strong>of</strong> exercise ECG reported that the maindiagnostic criterion (ST depression) performed only moderately well, with a PLR <strong>of</strong> 2.79 for a 1-mm cut-<strong>of</strong>f<strong>and</strong> 3.85 for a 2-mm cut-<strong>of</strong>f. The negative likelihood ratios were 0.44 <strong>and</strong> 0.72, respectively. All <strong>of</strong> theincluded studies were <strong>of</strong> patients with chronic chest pain. We identified no studies that compared exerciseECG to ICA for the diagnosis <strong>of</strong> CAD in patients presenting with acute symptoms due to suspected ACS.We are therefore unable to determine whether the diagnostic accuracy <strong>of</strong> exercise ECG estimated inpatients with stable symptoms can be extrapolated to those presenting with suspected ACS.Prognostic accuracy <strong>of</strong> computed tomographic coronary angiography <strong>and</strong>exercise electrocardiography for predicting major adverse cardiac eventsWe identified seven studies that evaluated the prognostic accuracy <strong>of</strong> CTCA for major cardiac events inpatients with suspected ACS. MACE rates were generally very low in patients with a negative CTCA butthis may reflect selection <strong>of</strong> low-risk patients rather than accurate risk stratification by CTCA. Most <strong>of</strong> theevents reported in patients with positive CTCA findings were process events (i.e. PCI or CABG), which, inan unblinded study, may simply reflect physicians acting on CTCA findings. However, one study 136 reportedan association between positive CTCA <strong>and</strong> MACEs (including revascularisation) despite patients <strong>and</strong>carers being blind to CTCA results. Furthermore, this study used multivariate <strong>analysis</strong> to show that CTCAfindings predicted MACEs even after adjustment for a clinical risk score incorporating ECG <strong>and</strong> troponin.This study therefore shows that CTCA can provide potentially useful additional prognostic information,beyond routine clinical assessment with ECG <strong>and</strong> troponin. Despite this, the overall findings <strong>of</strong> our <strong>review</strong>suggested only weak evidence that CTCA findings predicted MACEs in patients with suspected ACS. The95% CrIs <strong>of</strong> estimates <strong>of</strong> the RR <strong>of</strong> MACEs associated with positive CTCA were wide <strong>and</strong> included thepossibility <strong>of</strong> no association.A previous systematic <strong>review</strong> <strong>and</strong> <strong>meta</strong>-<strong>analysis</strong> by Hulten et al. 174 sought all prognostic studies <strong>of</strong> CTCArather than just studies <strong>of</strong> patients with suspected ACS. Most studies included patients with stablesymptoms rather than suspected ACS. Only the study by Rubinshtein et al. 135 was included in this <strong>review</strong><strong>and</strong> ours. Hulten et al. 174 included 18 studies evaluating 9592 patients with a median follow-up <strong>of</strong>20 months. The pooled annualised event rate for obstructive (any vessel with 50% luminal stenosis)compared with normal CTCA was 8.8% compared with 0.17% per year for MACEs (p < 0.05) <strong>and</strong> 3.2%compared with 0.15% for death or MI (p < 0.05). These findings suggest that abnormalities on CTCApredict an increased risk <strong>of</strong> a MACE in patients with suspected CAD <strong>and</strong> that the risk <strong>of</strong> MACEs is very lowif CTCA is normal. Our <strong>review</strong> confirms that the low risk <strong>of</strong> a MACE associated with CTCA is also seen inpatients with suspected ACS but the low overall rate <strong>of</strong> adverse outcome means that we cannot be surewhether this reflects low-risk patient selection or effective risk stratification by CTCA.We identified 13 studies reporting risk <strong>of</strong> MACEs after ETT for patients presenting to hospital withsuspected ACS. Overall, MACE rates were generally low among patients with negative ETT results.There was some evidence that positive tests identified higher-risk patients <strong>and</strong> were associated with aneightfold increase in the risk <strong>of</strong> a MACE. However, as with CTCA, in unblinded studies higher rates <strong>of</strong>revascularisation among patients with positive ETT may reflect physician awareness <strong>and</strong> expectation <strong>of</strong> a© 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. 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