Effect of Hemolysis on the Cardiac Troponin I and Creatinine Assay on the Siemens Dimension Vista Analyzer
Background: Cardiac troponin (cTn) and creatinine concentrations are critical to support the emergency department in the diagnosis of acute myocardial infarction and management of stroke. Pre-analytical conditions that affect the accuracy of results jeopardize patient care. Investigators have reported that as high as 8.8% of the specimens collected in the emergency department are hemolyzed and that hemolysis can cause a negative interference in cTn concentration, but no current studies on the impact of hemolysis on cTn I or creatinine concentration on the Siemens Dimension Vista® using lysed erythrocytes (hemolysate) have been published. Here, we evaluate the effect of hemolysis on the Siemens Dimension Vista cTnI and creatinine assays. Hemolysis effect on the Beckman Synchron DxC® creatinine assay was also studied.
Methods: Discarded serum specimens were used to create low, borderline and high pools for cTnI and creatinine. Target average concentration for the low, medium and high pools were < 0.04 ng/mL, 0.04-0.20 ng/mL, and >0.2 ng/mL for cTnI, and 0.3-0.8 mg/dL, 1.2-1.5 mg/dL, and 4.5-5.5 mg/dL for creatinine. The cTnI medium pool and the creatinine low pool were intentionally created to overlap the clinical decision limits for ruling out myocardial infarction or examine renal function in stroke patients. A hemolysate was obtained by treating an ethylenediaminetetraacetic acid plasma specimen to one freeze-thaw cycle. Increasing volumes of the hemolysate (1, 5, 10, 20, and 50 uL) were added to each of five aliquots of each pool. The final Hb concentration was estimated based on the hemolysis index (range 5 - 600 mg/dL; Hb index 4 = 100-200 mg/dL). cTnI and creatinine concentrations were measured in triplicate. Siemens Dimension Vista cTnI assay is a homogeneous luminescent oxygen channeling immunoassay. The analytical measurable range (AMR) is 0.015-40 ng/ml. The Siemens Dimension Vista and the Beckman Synchron DxC creatinine assays use the modified kinetic Jaffe reaction to measure a red chromophore at 510-520 nm. ThAMR for the Siemens Dimension Vista and the Beckman Synchron DxC are 0.2-20 mg/dL and 0.1-25 mg/dL respectively. The average concentration for each aliquot was subtracted from the baseline (no added hemolysate). Recovery was calculated as a percentage of the baseline concentration. Recovery of 100±5% and 100±10% was considered acceptable for cTnI and creatinine respectively.
Results: Moderate hemolysis produces a negative interference in the cTnI and creatinine assays in a concentration-dependent manner. For the Siemens Dimension Vista, % recovery for cTnI for the medium pool was 100 mg/dL, and150 mg/dL. Recovery for creatinine for the low and medium pools was < 90% at Hb concentrations > 200 mg/dL. The Beckman creatinine % recovery was acceptable for all the pools in the presence of up to 600 mg/dL of Hb.
Conclusions: We have demonstrated that hemolysis may compromise the diagnosis of acute myocardial infarction and the management of stroke. Moderate hemolysis decreased cTnI and creatinine concentrations at the medical decision limits. Clinicians should be cautioned on the interpretation of cTnI and creatinine concentrations in specimens presenting moderate hemolysis.
Published In/Presented At
Ali, S. Roquero, L. Feldkamp, C. S., Zajechowski, J. Dolland. J. Vasudev, V. I., Luzzi. (2011). Effect of Hemolysis on the Cardiac Troponin I and Creatinine Assay on the Siemens Dimension Vista Analyzer. Presentation Presented at: American Association for Clinical Chemistry (AACC), Atlanta, Georgia.
Medical Pathology | Pathology
Department of Medicine, Department of Medicine Faculty, Department of Pathology and Laboratory Medicine, Pathology Laboratory Medicine Faculty