Author + information
- Peter A. Kavsak, PhD⁎ ( and )
- Andrew Worster, MD
- ↵⁎Juravinski Hospital and Cancer Centre (Core Lab Section), 711 Concession Street, Hamilton, Ontario L8V 1C3, Canada
We read with great interest the paper by Body et al. (1) that presented intriguing data on a possible early rule-out protocol for acute myocardial infarction in patients presenting with undetectable cardiac troponin T (cTnT) measured with the high-sensitivity assay ([hs-cTnT], undetectable <3 ng/l). Using this approach, nearly one-quarter of the population could be ruled out for acute myocardial infarction at presentation with, the investigators contend, possibly no need for serial troponin testing in this group (1). However, at these lower concentrations, there are other important factors, in addition to imprecision, that need to be considered. First, there is no standardization in reporting hs-cTnT results, with different laboratories using different cutoffs and lower limits for reporting (e.g., limit of the blank [LoB] = 3 ng/l, which Body et al. used versus limit of detection = 5 ng/l) (2). It would be interesting to see how this rule-out algorithm would change if the higher limit of detection of 5 ng/l were used as opposed to the LoB of 3 ng/l.
Second, the presence of hemolysis will also negatively affect the cTnT concentrations, with larger concentrations of hemoglobin resulting in proportionally lower cTnT concentrations (3). This is not a trivial problem, as a recent audit in our hospital over 1 month identified over 10% (217 of 2,085) of cTnT results were on hemolyzed samples. Thus, for hemolyzed specimens whose reported hs-cTnT concentrations are <3 ng/l, a repeat specimen may be required to confirm that the cTnT concentration is truly below the LoB and not due to this negative interferent.
Third, this approach of using the LoB to rule out acute myocardial infarction may not be transferable to other assays that are perhaps more analytically sensitive. For example, in a cohort of chest pain patients presenting early to an emergency department, more than 25% of these patients had hs-cTnT concentrations below the LoB; however, in contrast, all of these patients had detectable cardiac troponin I concentrations as measured with an investigational-use high-sensitivity cardiac troponin I assay (4). It is clear from the work of Body et al. (1) that changes in how we use and report high-sensitivity cardiac troponin assays are required to achieve the most optimum care for patients presenting with chest pain. However, the true benefit for early rule-out may be less than reported after including other important outcomes requiring hospital admission (i.e., all of the major adverse cardiac events) and after considering important analytical issues.
Please note: Dr. Kavsak has received grants/honorarium from Abbott, Beckman Coulter, Ortho Clinical Diagnostics, Randox, and Roche.
- American College of Cardiology Foundation
- Body R.,
- Carley S.,
- McDowell G.,
- et al.
- Kavsak P.A.,
- Hill S.A.,
- Bhanich Supapol W.,
- Devereaux P.J.,
- Worster A.