Optimizing the availability of 'stat' laboratory tests using Shewhart 'C' control charts.
We describe a general strategy for optimizing the availability of 'stat' out-of-hours laboratory tests to the particular clinical needs of health care institutions. We initially introduced a consensus menu of 'stat' tests and prospectively monitored for 5 years all additional requests for 'stat' clinical biochemistry tests in a metropolitan tertiary referral university teaching hospital. Laboratory staff triaged 'stat' requests, and clinical biochemistry consultants reviewed requests not already performed routinely. The frequency of these requests was monitored on a Shewhart 'c' control chart. A quality system certified to ISO 9001 was used to assure laboratory compliance with procedures. Various interventions were tested using the Shewhart 'c' control chart to monitor their effectiveness. Matching the timing of analytical assays with the time of sample collection had no significant effect on the number of 'stat' requests. Implementation of a hospital-wide laboratory information system also had no significant effect on the number of 'stat' requests. The most effective strategy consisted of optimization of the test menu to match request patterns, combined with the introduction of a laboratory quality system. Within our institution, this strategy resulted in a sevenfold reduction in 'stat' requests, from one per 2,200 specimens to fewer than one per 32,000 specimens.