Troponin Testing Presents Problems in Kidney-Impaired People

High-sensitivity cardiac troponin (hs-cTn) assays have improved the diagnosis of myocardial infarction in patients with healthy kidney function and are now widely used in clinical practice.

However, in patients with kidney impairment, long-term elevations in troponin levels are common, and interpretation can be more challenging. As such, the effect of implementing hs-cTn testing on the diagnosis and outcomes of patients with kidney impairment is uncertain.

Medical Scientists at the University of Edinburgh (Edinburgh, Scotland) and their colleagues evaluated the use of a hs-cTnI assay in consecutive patients with suspected acute coronary syndrome across 10 hospitals in a stepped-wedge, cluster-randomized clinical trial of 46,927 consecutive patients. Throughout the trial, cTnI was measured using contemporary and high-sensitivity assays the ARCHITECT_STAT, Abbott Laboratories, Abbott Park, IL, USA). Estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration equation. Kidney impairment was defined as an eGFR of less than 60 mL/min/1.73 m².

The team reported that overall, hs-cTnI concentrations were elevated in 10,111 patients (22%), of whom 42% had kidney impairment. These newer assays flagged six fold more patients as kidney function declined from an eGFR of at least 90 to less than 30 mL/min/1.73 m² (10% versus 66%). However, the proportion with acute type 1 myocardial infarction (MI) dropped precipitously across that same range of renal function, from 74% to 35%.

In addition, the increase in identification did not correlate with better outcomes. Subsequent type 1 or 4b (more than 24 hours after percutaneous coronary intervention) MI or cardiovascular death were equally common at one year for patients treated before and after clinical use of the high-sensitivity test both with kidney impairment (25% versus 24%; adjusted hazard ratio [HR] = 1.00) and without it (13% versus 11%; adjusted HR = 0.89).

Patients reclassified as having elevated troponin with the more sensitive versus conventional assay also did not have better outcomes. Nicholas L. Mills, MD, a consultant cardiologist and senior author of the study said, “The reasons for this are complex. Two-thirds of patients with kidney impairment and elevated hs-cTnI concentrations had a diagnosis other than type 1 myocardial infarction. In the absence of evidence from randomized trials, there is little guidance to inform clinical decisions for this heterogeneous group.” The study was published on June 7, 2021, in the journal JAMA Internal Medicine.

Related Links:
University of Edinburgh
Abbott Laboratories