Jaffe, Allan S.

High-sensitivity cardiac troponin assays enable cardiac troponin measurement with a high degree of analytical sensitivity and a low level of analytical imprecision at the low measuring range. One of the most important advantages of these new assays is that they allow novel, more rapid approaches for ruling in or ruling out acute myocardial infarctions. The increase in the early diagnostic sensitivity of high-sensitivity cardiac troponin assays comes at the cost of a reduced acute myocardial infarction specificity of the biomarker, because more patients with other causes of acute or chronic myocardial injury without overt myocardial ischaemia are detected than with previous cardiac troponin assays. Increased troponin concentrations that do not fit with the clinical presentation are seen in the daily routine, mainly as a result of a variety of pathologies, and if tested in the same sample, even discrepancies between high-sensitivity cardiac troponin I and troponin T test results may sometimes be found as well. In addition, analytically false-positive test results occasionally may occur since no assay is perfect. In this review, we summarise the biochemical, pathophysiological and analytical background of the work-up for such a clinical setting.

BACKGROUND: This study sought to determine whether preoperatively measured high-sensitivity cardiac troponin T (hs-cTnT) and N -terminal pro-brain natriuretic peptide (NT-proBNP) improve cardiac risk prediction in patients undergoing major noncardiac surgery compared with the standard risk indices. METHODS: In this ancillary study to the Vitamins in Nitrous Oxide trial, patients were included who had preoperative hs-cTnT and NT-proBNP measured (n = 572). Study outcome was the incidence of postoperative myocardial infarction (MI) within the first 3 postoperative days. hs-cTnT was considered elevated if >14 ng/L and NT-proBNP if >300 ng/L. Additional cutoff values were investigated on the basis of receiver operating characteristic statistics. Biomarker risk prediction was compared with Lee’s Revised Cardiac Risk Index (RCRI) with the use of standard methods and net reclassification index. RESULTS: The addition of hs-cTnT (>14 ng/L) and NT-proBNP (>300 ng/L) to RCRI significantly improved the prediction of postoperative MI (event rate 30/572 [5.2%], Area under the receiver operating characteristic curve increased from 0.590 to 0.716 with a 0.66 net reclassification index [95% confidence interval 0.32–0.99], P < .001). The use of 108 ng/L as a cutoff for NT-proBNP improved sensitivity compared with 300 ng/L (0.87 vs 0.53). Sensitivity, specificity, positive, and negative predictive value for hs-cTnT were 0.70, 0.60, 0.09, and 0.97 and for NT-proBNP were 0.53, 0.68, 0.08, and 0.96. CONCLUSIONS: The addition of cardiac biomarkers hs-cTnT and NT-proBNP to RCRI improves the prediction of adverse cardiac events in the immediate postoperative period after major noncardiac surgery. The high negative predictive value of preoperative hs-cTnT and NT-proBNP suggest usefulness as a “rule-out” test to confirm low risk of postoperative MI.