In patients with renal disease (GFR <60) presenting with possible acute coronary syndrome, high-sensitivity troponin (hs-TN) can still be used to identify those who are low-risk. But the overall percentage deemed low risk was much lower, as was specificity, in patients with renal impairment.
Why does this matter?
We know that patients with CKD often have persistent elevations in troponin. Is this due to chronic, smoldering heart disease or due to decreased clearance? We don't know. What we do know is that hs-Tn assays can detect even lower levels. This leads to more people with renal disease who have a positive troponin that is unrelated to having a MI. So is hs-Tn useful at all for risk stratification of patients who present with possible ACS who have renal impairment?
Negative is still negative, just not as often
This was a prospective multi-center study that examined 4726 patients presenting with suspicion for acute coronary syndrome (ACS); 904 patients had renal disease (defined as GFR <60). Using the hs-Tn-I (Abbott assay) cutoff of <5ng/L, only 17% of patients with renal disease were considered low risk on this basis vs 56% of patients with no renal disease. Sensitivity (98.9%) and negative predictive value (98.4%) were virtually the same for the primary outcome of MI or cardiac death at 30 days. When using hs-Tn >99th percentile to identify high risk patients, specificity (70.9%) and positive predictive value (50.0%) were much lower for patients with renal disease. Having a hs-Tn >99th percentile (16 ng/L for women and 34 for men) was a bad prognostic indicator for those with renal disease; 24% had MI or cardiac death at 1 year vs. 10% for patients with the same troponin elevation but no renal disease (hazard ratio 2.19). Patients with renal disease more often had other comorbid conditions, so the above hazard ratio was adjusted for age, sex, diabetes, ischemic heart disease, and hypertension. CKD was an independent risk factor for adverse cardiac events at 1 year follow up.
High-Sensitivity Cardiac Troponin and the Risk Stratification of Patients With Renal Impairment Presenting With Suspected Acute Coronary Syndrome. Circulation. 2018 Jan 30;137(5):425-435. doi: 10.1161/CIRCULATIONAHA.117.030320. Epub 2017 Oct 4.
Peer reviewed by Thomas Davis, MD.