High sensitivity cTnI results are used to assist in the diagnosis of acute myocardial infarction and to aid in the risk stratification of patients with acute coronary syndromes with respect to their relative risk of mortality [1-6].
Precision at low concentrations
The imprecision profile at low concentrations was determined by using plasma samples. The within-run and total standard deviations were calculated by CLSI EP5-A2 guidelines. The following results were obtained:
Sensitivity and measurable normal value
The limit of blank (LoB) and the limit of detection (LoD) of the PATHFASTTM hs-cTnI assay were determined, where LoB was 1.23 ng/L and LoD was 2.33 ng/L. The limit of quantitation (LoQ) at 20% coefficient of variation (CV) was determined to be 4 ng/L. The limit of quantitation (LoQ) at 10% coefficient of variation (CV) was determined to be 15 ng/L. These results were obtained from plasma samples.
The measurable number of healthy subjects between LoD and 99th percentile was 487 from 734 healthy subjects, in whom cardiovascular diseases were excluded by the following criteria: age <18; HbA1c ≥6.5%; NTpro-BNP ≥125 ng/L <75; NTpro-BNP ≥450 ng/L ≥75 years; eGFR <60 mL/min/1.73m².
PATHFASTTM hs-cTnI was classified as a high sensitive assay according to IFCC guidelines. With PATHFASTTM hs-cTnI assay classified as a high sensitivity assay, the gender specific 99th percentile and the measurable number of healthy subjects between LoD and 99th percentile were identified .
The reference interval for the PATHFASTTM hs-cTnI assay was determined by testing 490 healthy individuals. The 99th percentile of the reference interval is 29 ng/L. The CV value at the 99th percentile concentration is 6.1% .
Diagnostic performance criteria
cTnI concentrations were measured by using the PATHFASTTM hs-cTnI assay in EDTA plasma samples obtained at 0 hour, 1 hour and 3 hours after admission to the chest pain unit (CPU) from 993 patients with suspicion of acute coronary syndrome. The final diagnosis identified 219 AMI patients (23.5%). The ROC analysis revealed AUC values for the discrimination between AMI and non-AMI patients including the clinical sensitivity and specificity, as well as the positive (PPV) and negative (NPV) predictive values based on the 99th percentile upper reference limit (URL) of 27.0 ng/L .
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- Cristenson et al. High-Sensitivity Cardiac Troponin I Assay for Point-of-Care or Laboratory Measurement: Pathfast® TnI-II System. TnI-II : in preparation.
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