Positive predictive value of a point-of-care testing strategy on first-draw specimens for the emergency department-based detection of acute coronary syndromes.
BACKGROUND
The rapid and accurate diagnosis of the etiology of chest pain is of central importance in the triage of patients presenting to emergency departments. The "first-draw" sensitivity of serum cardiac markers is known to be low on initial presentation; however, less is understood regarding the predictive value of a positive test in this situation.


OBJECTIVE
To determine the ability of a critical pathway combining medical history and physical examination, electrocardiographic findings, point-of-care testing, and central laboratory data to accurately predict the presence of acute coronary ischemia.


METHODS
We investigated the positive predictive value of a testing algorithm for first-draw specimens in clinical practice, combining a qualitative, point-of-care, triple-screen testing panel for cardiac markers, including myoglobin, creatine kinase-MB, and cardiac troponin I, with confirmation of the rapid assay in the central hospital laboratory by quantitative assays for creatine kinase-MB and cardiac troponin T.


RESULTS
While a positive result on any of the individual cardiac markers of the point-of-care test had a positive predictive value for the acute coronary syndrome of only 36% (creatine kinase-MB, 41%; myoglobin, 36%; and troponin I, 65%), the positive predictive value for the diagnosis of acute coronary syndrome increased to 76% if all 3 point-of-care markers were simultaneously positive. The positive predictive value for acute coronary syndrome for a positive confirmatory result in the hospital laboratory for either creatine kinase-MB or cardiac troponin T was 61%. Among those patients with a positive marker on both the point-of-care test and the laboratory test, a careful retrospective review of the clinical history (with exclusion of patients with nonischemic cardiac pathologies and renal insufficiency) increased the positive predictive value of this algorithm to 98%.


CONCLUSIONS
Our data suggest that qualitative, point-of-care, triple-screen cardiac marker testing of patients with chest pain at initial presentation may exhibit relatively low positive predictive values. Positive predictive value can be significantly improved by rapid confirmation in the hospital laboratory and careful review of clinical findings.
Kratz
Alexander
A
Division of Laboratory Medicine, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
Januzzi
James L
JL
Lewandrowski
Kent B
KB
Lee-Lewandrowski
Elizabeth
E
D002637:Chest Pain / Q000175:diagnosis*; D003402:Creatine Kinase / Q000097:blood*; D052279:Creatine Kinase, MB Form; D004630:Emergencies; D006801:Humans; D007527:Isoenzymes / Q000097:blood*; D017202:Myocardial Ischemia / Q000175:diagnosis*; D009211:Myoglobin / Q000097:blood*; D019095:Point-of-Care Systems; D020107:Troponin T / Q000097:blood*
D007527:Isoenzymes; D009211:Myoglobin; D020107:Troponin T; D003402:Creatine Kinase; D052279:Creatine Kinase, MB Form