Cardiac troponin I measurement with the ACCESS® immunoassay system: analytical and clinical performance characteristics

Abstract

We evaluated the ACCESS® cardiac troponin I (cTnI) immunoassay as a marker for myocardial infarction (MI). Total imprecision was 6.0% to 13.5%, the minimum detectable concentration was 0.007 μg/L, and the limit of quantitation was 0.046 μg/L. Comparison of cTnI measurement between the ACCESS and Stratus systems (n = 114) showed a proportional difference: ACCESS cTnI = 0.0996 Stratus cTnI + 0.049 μg/L (r = 0.811). Fifty-nine of 61 ambulatory patients without cardiac symptoms had no detectable cTnI (95% range, 0.00 to 0.025 μg/L). The optimum cutoff for discriminating MI (n = 289, 45 with MI) was 0.15 μg/L by receiver operator characteristic curve analysis; at this cutoff, the ACCESS cTnI assay showed a sensitivity of 88.9% (95% CI, 79.7–98.1%) and specificity of 91.8% (95% CI, 88.4–95.2%). The ACCESS cTnI assay results showed 89.4% and 93.0% concordance with the MB isoenzyme of creatine kinase (CK-MB) mass and Stratus cTnI results, respectively, for classification of patients with suspected MI. The ACCESS cTnI assay appears to show sensitivity and specificity comparable with those of both CK-MB mass and Stratus cTnI assays for the diagnosis of MI in patients presenting within 12 h of onset of symptoms.

Cardiac Troponin-I Concentration in Dogs with Cardiac Disease

“…Cardiac troponin is tightly bound to the sarcomeric actin filament, and without cardiac damage, circulating cTnI concentrations in healthy subjects are low. 25,26 Our finding that healthy dogs have cTnI near or below the lower detection limit of the assay agrees with previous reports in human 57,58 and veterinary medicine. 13,14,19,20 Specifically, our median cTnI of 0.03 ng/mL in 176 healthy dogs is comparable to that of a previous study that reported a median cTnI of 0.02 ng/mL in 41 clinically healthy dogs.…”

“…The concentration of circulating cTnI is a balance between its release from the myocardium; leakage into the general circulation; degradation by serum proteases; and clearance by the kidney, liver, and reticuloendothelial system. In humans with chronic renal failure (serum creatinine Ͼ8.0 mg/dL), troponin concentrations can be high due to decreased renal clearance, 57 but this effect apparently is more significant for cTnT measurement than for cTnI. 62 We did not specifically perform renal function tests in our study population, but given the high prevalence of chronic renal disease in older dogs, it is possible that impaired clearance of cTnI influenced our findings.…”

Myocardial ischaemia in normal patients undergoing elective Caesarean section: a peripartum assessment

“…The reference ranges and cut‐offs that we adopted were based upon the experiences of our biochemistry department and on a published evaluation by Christenson et al . [13] and were as follows: (i) lower limit of detection = 0.03 ng.ml −1 , (ii) cut‐off for myocardial infarction = > 0.15 ng.ml −1 , (iii) grey area indicating possible ischaemia = 0.07–0.15 ng.ml −1 .…”

The risk of cardiac injury during laparoscopic fundoplication: cardiac troponin I and ECG study Note

“…The ACCESS ® Troponin I Immunoassay is a double‐monoclonal immunoenzymometric assay for quantitative determination of cardiac troponin I using magnetic separation and chemoluminescence detection and is based on the technique described by Larue et al ( 8). The results with this analytical system are available within 15 min and, according to the manufacturer’s specifications, the analytical range is 0.03–50.0 ng · ml −1 and the cut‐off value is 0.1 ng · ml −1 to be considered as the biochemical evidence of myocardial injury ( 9). If the patient expressed some precordial pain or ECG disturbance in comparison with basal ECG associated with specific cardiac enzyme impairment, a cardiologist and transthoracic echocardiography were required.…”