Comparison of emergency department patient classification by point-of-care and central laboratory methods for cardiac troponin I
Jay L Bock1, Adam J Singer, Henry C Thode
1Department of Pathology, Stony Brook University, Stony Brook, NY 11794-7300, USA.
Insights
Rapid point-of-care whole blood cardiac troponin I testing generally aligns with central laboratory plasma assays for acute coronary syndrome. However, it may miss minor elevations and produce some false positives.
Area of Science:
- Clinical diagnostics
- Cardiovascular medicine
- Biomarker analysis
Background:
- Acute coronary syndrome (ACS) diagnosis relies on cardiac troponin I (cTnI) levels.
- Point-of-care testing (POCT) offers rapid results but requires validation against central laboratory assays.
Purpose of the Study:
- To compare the diagnostic performance of a rapid, whole blood POCT assay for cTnI against a central laboratory plasma assay.
- To evaluate the reliability of POCT for patient classification in emergency department settings.
Main Methods:
- Prospective comparison of Abbott i-STAT whole blood cTnI (Tn-P) with Siemens TnI-Ultra plasma assay (Tn-U) in emergency department patients with suspected ACS.
- Retesting of elevated Tn-P results and a random selection of negative Tn-P results using Tn-U.
Main Results:
- Of 5,909 initial Tn-P tests, 573 (9.7%) were elevated. Of these, 4.5% retested negative by Tn-U.
- The Tn-U assay generally yielded higher results (approx. 50%) and had a lower 99th percentile cutoff than Tn-P.
- 5.8% of initially negative Tn-P results retested as elevated by Tn-U, with low levels (<0.1 ng/mL).
Conclusions:
- Rapid whole blood cTnI POCT provides generally reliable patient classification compared to central laboratory plasma assays.
- The POCT assay may miss subtle elevations in cTnI and can produce false positives, necessitating careful interpretation.
Abstract:
For patients admitted to the emergency department (ED) with suspected acute coronary syndrome, we compared results of a rapid, point-of-care whole blood assay for cardiac troponin I (Abbott i-STAT, Abbott Point-of-Care, East Windsor, NJ) (Tn-P) with an automated central laboratory plasma assay (Siemens TnI-Ultra, Siemens Medical Solutions Diagnostics, Tarrytown, NY) (Tn-U). Clinical data were obtained during a 6-month period during which ED patients were screened by Tn-P, with retesting of elevated results by Tn-U. Of 5,909 Tn-P results, 573 (9.7%) were elevated; these and a random selection of 137 negative specimens were retested by Tn-U. Of the specimens with elevated results, 4.5% retested negative by Tn-U, even though Tn-U typically gave about 50% higher results and had a lower manufacturer-specified 99th percentile cutoff. Of the negatives, 5.8% retested as elevated by Tn-U, but with levels no higher than 0.1 ng/mL (0.1 microg/L). Rapid whole blood testing for cardiac troponin I gave generally reliable patient classifications compared with plasma testing in the central laboratory, but besides missing small elevations, produced some apparent false-positives.
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