Towards evidence-based emergency medicine: best BETs from the Manchester Royal Infirmary. Pregnancy-associated plasma protein A: a novel cardiac marker with promise

Pregnancy Associated Plasma Protein-A as a Cardiovascular Risk Marker in Patients with Stable Coronary Heart Disease During 10 Years Follow-Up-A CLARICOR Trial Sub-Study

Elevated pregnancy-associated plasma protein A (PAPP-A) is associated with mortality in acute coronary syndromes. Few studies have assessed PAPP-A in stable coronary artery disease (CAD) and results are conflicting. We assessed the 10-year prognostic relevance of PAPP-A levels in stable CAD. The CLARICOR trial was a randomized controlled clinical trial including outpatients with stable CAD, randomized to clarithromycin versus placebo. The placebo group constituted our discovery cohort (n = 1.996) and the clarithromycin group the replication cohort (n = 1.975). The composite primary outcome was first occurrence of cardiovascular event or death. In the discovery cohort, incidence rates (IR) for the composite outcome were higher in those with elevated PAPP-A (IR 12.72, 95% Confidence Interval (CI) 11.0-14.7 events/100 years) compared to lower PAPP-A (IR 8.78, 8.25-9.34), with comparable results in the replication cohort. Elevated PAPP-A was associated with increased risk of the composite outcome in both cohorts (discovery Hazard Ratio (HR) 1.45, 95% CI 1.24-1.70; replication HR 1.29, 95% CI 1.10-1.52). In models adjusted for established risk factors, these trends were attenuated. Elevated PAPP-A was associated with higher all-cause mortality in both cohorts. We conclude that elevated PAPP-A levels are associated with increased long-term mortality in stable CAD, but do not improve long-term prediction of death or cardiovascular events when added to established predictors.

The utility of pregnancy-associated plasma protein A for determination of prognosis in a cohort of patients with coronary artery disease

Background: Pregnancy-associated plasma protein-A (PAPP-A) is discussed as a biomarker representing unstable plaques in coronary artery disease (CAD). Methods: In this study 927 patients with CAD (534 with stable angina and 393 with acute coronary syndrome [ACS]) and 217 patients without CAD and measured PAPP-A levels were included. Follow-up for a median of 5 years was documented. Results: Rising quartiles of PAPP-A concentration had a higher cardiovascular mortality in the overall cohort of patients with CAD (p = 0.002) and the cohort with ACS (p = 0.01). Patients with suspected ACS below the LOD for troponin I but elevated PAPP-A levels had an increased cardiovascular mortality. A cut-off of 11.4 IU/l identified patients with a higher mortality during follow-up. Conclusion: Rising PAPP-A levels are prognostic in patients with CAD. PAPP-A levels were especially predictive in ACS patients with troponin below 10% CV of the 99th percentile for cardiovascular mortality.

Novel biomarkers in diagnosing cardiac ischemia in the emergency department: a systematic review

BACKGROUND

Novel biomarkers of myocardial ischemia and inflammatory processes have the potential to improve diagnostic accuracy of acute coronary syndrome (ACS) within a shorter time interval after symptom onset.

OBJECTIVE

The objective was to review the recent literature and evaluate the evidence for use of novel biomarkers in diagnosing ACS in patients presenting with chest pain or symptoms suggestive of cardiac ischemia to the emergency department or chest pain unit.

METHODS

A literature search was performed in MEDLINE, EMBASE, Cochrane DSR, ACP Journal Club, DARE, CCTR, CMR, HTA, and NHSEED for studies from 2004 to 2010. We used the inclusion criteria: (1) human subjects, (2) peer-reviewed articles, (3) enrolled patients with ACS, acute myocardial infarction or undifferentiated signs and symptoms suggestive of ACS, and (4) English language or translated manuscripts. Two reviewers conducted a hierarchical selection and assessment using a scale developed by the International Liaison Committee on Resuscitation.

RESULTS

Out of a total 3194 citations, 58 articles evaluating 37 novel biomarkers were included for final review. Forty-one studies did not support the use of their respective biomarkers. Seventeen studies supported the use of 5 biomarkers, particularly when combined with cardiac-specific troponin: heart fatty acid-binding protein, ischemia-modified albumin, B-type natriuretic peptide, copeptin, and matrix metalloproteinase-9.

CONCLUSION

In patients presenting to the emergency department with chest pain or symptoms suggestive of cardiac ischemia, there is inadequate evidence to suggest the routine testing of novel biomarkers in isolation. However, several novel biomarkers have the potential to improve the sensitivity of diagnosing ACS when combined with cardiac-specific troponin.