How to Interpret Positive Troponin Tests in CKD

Q) Recently, when I have sent my patients with chronic kidney disease (CKD) to the emergency department (ED) for complaints of chest pain or shortness of breath, their troponin levels are high. I know CKD increases risk for cardiovascular disease, but I find it hard to believe that every CKD patient is having an MI. What gives?

Cardiovascular disease remains the most common cause of death in patients with CKD, accounting for 45% to 50% of all deaths. Therefore, accurate diagnosis of acute myocardial infarction (AMI) in this patient population is vital to assure prompt identification and treatment.^1,2

Cardiac troponins are the gold standard for detecting myocardial injury in patients presenting to the ED with suggestive symptoms.¹ But the chronic baseline elevation in serum troponin levels among patients with CKD often results in a false-positive reading, making the detection of AMI difficult.¹

With the recent introduction of high-sensitivity troponin assays, as many as 97% of patients on hemodialysis exhibit elevated troponin levels; this is also true for patients with CKD, on a sliding scale (lower kidney function = higher baseline troponins).² The use of high-sensitivity testing has increased substantially in the past 15 years, and it is expected to become the benchmark for troponin evaluation. While older troponin tests had a false-positive rate of 30% to 85% in patients with stage 5 CKD, the newer troponin tests display elevated troponins in almost 100% of these patients.^1,2

Numerous studies have been conducted to determine the best way to interpret positive troponin tests in patients with CKD to ensure an accurate diagnosis of AMI.² One study determined that a 20% increase in troponin levels was a more accurate determinant of AMI in patients with CKD than one isolated positive level.³ Another study demonstrated that serial troponin measurements conducted over time yielded higher diagnostic accuracy than one measurement above the 99th percentile.⁴