"There are differences between (Food and Drug Administration)-cleared high-sensitivity troponin assays when stratifying patients with suspected ACS which is especially important when a patient is transferred from one hospital to another," Dr. Julia Karady of Massachusetts General Hospital, Harvard Medical School, in Boston, told Reuters Health by email.
"In these instances, if different assays were used for troponin measurement, one may need to carefully reevaluate clinical history," she said.
The three hs-cTn assays approved in the United States are the Elecsys 2010 platform from Roche Diagnostics; ARCHITECT i2000SR from Abbott Diagnostics; and HsVista from Siemens Diagnostics.
Dr. Karady and colleagues quantified differences between the assays for common analytic benchmarks - < limit of detection (<LOD), LOD to 99th percentile and >99th percentile - and the potential impact of those differences on management of patients with suspected ACS.
They analyzed 1,027 blood samples taken at emergency department (ED) presentation or at two and four hours after ED presentation from 624 patients (mean age, 53 years; 39% women) with suspected ACS from the ROMICAT I and II trials.
Classification as <LOD differed significantly between the Roche, Abbott, and Siemens assays, at 56.3%, 10.4%, and 41.2%, respectively (P<0.001).
The assays also differed significantly in classification of LOD to 99th percentile (36.5%, 83.5%, and 52.6%, respectively; P<0.001).
The proportion classified >99th percentile did not differ significantly (7.2%, 6.0%, and 6.2%; P=0.114).
"We did not expect to see a discordance to this extent, which was more striking in the per-blood-sample analysis where only one time point troponin measurement was used (overall agreement: 37.4%), but improved when serial troponin measurements were taken into account in the per-patient analysis (overall agreement: 74.8%)," Dr. Karady told Reuters Health.
Comparison of the three assays in patients with suspected ACS found "up to 2-fold differences in results that could influence the proportion of patients referred for further observation or investigation," the researchers report in the Journal of the American College of Cardiology.
Furthermore, Dr. Karady told Reuters Health, the results show "differences between the sexes that affect the level of agreement between assays and thus subsequent management decisions, as assays differed significantly more among females."
The results, she said, also suggest "around a 20% positivity rate" of non-invasive diagnostic tests (either obstructive CAD detected with coronary CT angiography or myocardial ischemia detected with SPECT) for those with an undetectable troponin concentration. This finding indicates that there is a "significant amount of underlying disease potentially unrecognized via hs-cTn testing."
Dr. Karady cautioned that this analysis included patients who presented to the ED with "intermediate likelihood for ACS; thus it is a highly selected patient population representing around 20% of the all-comer ED acute chest pain population - not including those at very low and very high risk for ACS. Therefore, these findings may apply only for those at intermediate likelihood for ACS."
The authors of an editorial in JACC say there are several take-home messages of this "well-done clinical investigation."
"First, 'let the buyer (i.e., the clinician) beware' when patients are transferred from one hospital to another, where different hs-cTn assays may be used at the two institutions. In such cases, careful clinical review and possibly additional diagnostic testing might be indicated," write Dr. Joseph Albert of the University of Arizona College of Medicine, in Tucson, and colleagues.
"Second, important differences between the sexes affect hs-cTn management decisions. Women have lower normal measurements, so a small increase in values that might be considered a normal variation in a male patient might have significance in a female patient. This is particularly relevant for the 'observe (gray zone)' hs-cTn values," they write.
The editorial writers agree with the study team that "clinicians should be aware of the discordances among commercially available hs-cTn assays when stratifying patients with suspected acute MI. Such disparities may result in different management recommendations."
The study had no commercial funding and the authors have no relevant disclosures.
SOURCE: https://bit.ly/3seERUT and https://bit.ly/3sflUBm Journal of the American College of Cardiology, online March 22, 2021.
By Megan Brooks
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