In absolute terms, analytic time for CLT is actually faster than POC testing. Most modern analyzers can produce results within 10 min or less from the time the sample is loaded and will then produce results at 30-s intervals thereafter. The majority of POC testing systems have comparable or slightly longer analytic times of10-15 min. In addition, although a POC testing system may have an analytic time of15 min, because it analyzes only one sample at a time, the effective analytic throughput of 4 samples/h will be much slower than the 50 (or more) samples/h of typical laboratory systems. The reason that POC testing can be overall a faster strategy is that the delays in sample transport and processing prior to analysis are removed. Prospective studies of POC testing have clearly shown a reduction in time to availability of results from a median of 71 (CLT) to 20 min (POC testing) (15) or from 71 min (CLT) to 24 (POC testing) (16). Another factor of importance is the impact of the availability of results. Results from the central laboratory may be available but not viewed. The evaluation of CLT uses the concept of turnaround time, i.e., the time from sample arrival to production of results. This is a limited measure of performance because it does not account for delays in sample arrival and action taken on the results. This has led to the concept of the therapeutic turnaround time, i.e., the time from sample draw to action on the results (17), sometimes referred to as vein-to-brain time. The therapeutic turnaround time is a more accurate assessment of the time to decision, but a better measure is the "brain-to-brain" time, i.e., the time from the decision to order a test to the action taken on the result (Fig. 3).
Brain-to-brain time represents part of the process of clinical care. It is this clinical process that determines the speed with which patient diagnosis is made and the appropriate clinical actions are taken, and, therefore (it is hoped), clinical outcomes are improved and cost efficiency is obtained. The actual analytic turnaround time may be a small component in this process. If the decision-making pathway is not optimized to act on rapidly produced test results, the speed of production of results will not be the rate-limiting step.
The importance of the clinical process and process reengineering cannot be overestimated. This process is well illustrated in the evolution of chest pain units that offer an alternative strategy to conventional approaches for the management of chest pain. Prospective observational (18-20) and randomized studies (21,22) have shown that such an approach is clinically equivalent to conventional strategies, diagnostically efficient, and cost-effective. This improvement has been achieved by process reengineering rather than POC testing. Data support the concept that more rapid provision of laboratory results will have a direct impact on outcome measures, such as length of stay. In a prospective observational study of a rapid diagnostic cardiac enzyme policy compared with a conventional strategy, there was a significant reduction in mean length of stay in the cardiac care unit, from 3 to 2 d (23). Provision ofa more frequent assay service showed a similar reduction (24). Conversely, a survey ofhospitals found that a more rapid and frequent assay service was associated with reduced length of stay for patients with a diagnosis of AMI, not, as might be expected, the low-risk "rule-out" patient (25).
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