Nearpatient testing

The incentive for near-patient testing should be the clinical need to return the results of investigations to the clinician as speedily as possible. This is a laudable, acceptable, and achievable aim.

There are many ways of addressing this problem (England.eta[ 1995; Machin etal 1996). Increasingly, laboratories are working extended-day or shift systems, as well as providing the traditional on-call services, to meet a 24-h demand. Similarly, rapid sample transport systems can eliminate the delays associated with portering. Any laboratory supporting an intensive care unit should be able to display or print the results of an investigation anywhere in the hospital within microseconds of completion of the analysis. These avenues should be explored and exploited to the full before alternatives are proposed.

Where these systems do not provide a sufficiently rapid return of results, it is appropriate to bring the equipment nearer to the patient. This equipment must give results of equal quality to those provided by the main laboratory. This excludes the superficially attractive, quick, and simple systems that may be appropriate to field medicine. The basic principles that should be followed have been outlined by England etal (1995). They include the strong recommendation that only instrumentation which employs primary sampling of whole blood should be employed for near-patient blood counting. Anything which involves dilution of whole blood in a preanalytical phase should be avoided. The reasons for this have nothing to do with the wish to maintain a professional closed shop and everything to do with the delivery of a service which will stand up to scrutiny.

The philosophy behind establishing near-patient testing must be based on a partnership between the clinical service and the laboratory. A service-level agreement which defines the range of services, operational details, and responsibilities of staff from both sides must be the basis on which this is established. The management of this service will need to involve staff from the laboratory and the clinicians concerned, but the professional head of the laboratory service must take the final responsibility for the quality of the service that is delivered. Training, equipment, safety, handling and logging of results, and quality control (both internal and external) must all be considered when such a service is established.

The point about defining the technological basis for something as simple as blood cell counting should be clear. It should not be undertaken lightly or ill-advisedly. It is not just a question of picking the right machine and plugging it in. After choosing the right machine to meet the specified clinical demand, the next step is to operate it properly. In general, the simpler or more basic (and cheaper) the counter, the more difficult this is. Conversely, the more sophisticated (and expensive) the machine, the more its operation will have been deskilled. All counters will require active quality control and must be operated in an environment in which detailed standard operating procedures have been laid down and where there is active quality control, interlaboratory quality assessment, and accreditation of the laboratory or operator.

Anyone can present a sample to an automated counter and obtain some results. Any competent lawyer can ask who is responsible for the procedure, where are the standard operating procedures, how are they maintained, how is their distribution controlled, who maintains the instrument, where are the instrument maintenance logs, where are the quality control results, what was the 'discriminant interval' for the last quality assessment, where are the quality assessment reports, where is the record of the laboratory procedure, and where is the report filed. A really good lawyer might start to ask who changed the sheath fluid container 6 months ago and what was the stated expiry date on the container. If you are not willing to bear the responsibility for being able to answer these questions and to spend the same time on this that the laboratory does, then do-it-yourself near-patient testing may not be for you.

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