The need for a point of care testing: an evidence-based appraisal.
The need for point of care testing (POCT) must be seen within the context of the need for biochemical diagnosis of patients suspected of acute coronary syndromes (ACS). The electrocardiogram is the initial test to select patients for thrombolysis and risk stratification. The majority of patients presenting with chest pain do not have AMI and diagnostic sensitivity of the ECG is only 55-75%. This means that biochemical diagnosis to confirm or exclude a diagnosis of acute myocardial infarction (AMI) is required for 90% of patients who present with suspected ACS. This can be achieved using myoglobin, creatine kinase and its MB isoenzyme and the cardiac troponins, cardiac troponin T and cardiac troponin I within 4-12 hours of admission, depending on the markers selected. Measurement of the cardiac troponins is superior to conventional tests as it allows risk stratification in patients with unstable angina in addition to a definitive diagnosis of AMI. Rapid diagnoses can have direct influence on length of stay and admission and discharge policies. The rationale for POCT is the improvement in analytical turnaround time (TAT). A number of systems for POCT have been developed ranging from conventional analysers used next to the patient to whole blood systems using immunochromatography. Laboratory and clinical evaluations of these systems have shown that they are accurate, equivalent to laboratory based diagnosis and can be related to outcome. In a prospective randomised controlled trial of POCT compared to laboratory testing we have shown improved TAT (20 minutes vs. 72 minutes) and significant reduction in hospital stay in patients randomised to POCT. Rapid diagnosis is effective and cost effective for patient management but only within the context of data driven decision-making protocols. The use of POCT will depend on the need for and the ability to achieve a rapid TAT for clinical decision making. POCT for cardiac markers has a definite place in management when very short TAT is required such as the ED. If the laboratory TAT exceeds 25% of the decision time, then POCT will be required. If therapeutic decisions are to be made, only POCT will be able to fulfil the TAT requirement.
Collinson
P O
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Department of Chemical Pathology, St George's Hospital, London, UK. poctrop@poctrop.demon.co.uk
D015415:Biomarkers; D003402:Creatine Kinase / Q000097:blood; D019317:Evidence-Based Medicine; D005260:Female; D017721:Hospital Costs; D006801:Humans; D007527:Isoenzymes; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D009203:Myocardial Infarction / Q000097:blood / Q000175:diagnosis*; D009211:Myoglobin / Q000097:blood; D019095:Point-of-Care Systems / Q000191:economics / Q000592:standards*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000097:blood; D020107:Troponin T / Q000097:blood
D015415:Biomarkers; D007527:Isoenzymes; D009211:Myoglobin; D019210:Troponin I; D020107:Troponin T; D003402:Creatine Kinase