Selecting instruments for the Stat lab.

The type of instrumentation and the way it's used are pivotal to a

laboratory's success in providing Stat service.

In recent years, laboratories have been expected to perform a greater number and variety of Stat tests. Hospital laboratories must meet the rapid tumaround-time requirements of outpatient treatment programs, same-day surgery, and such sophisticated techniques as transplant surgery. Reference laboratories, facing stiff competition, court physicians with such enhanced services as satellite Stat facilities.

All of this comes at a time when drastic changes in the reimbursement structure are exerting significant cost pressures on laboratories. Labs must not only provide a wide range of Stat analyses but also perform the tests cost-effectively. Furthermore, Stat testing must be integrated into the work flow in a way that minimizes disruption of normal operations.

Many laboratories performing routine testing do not have the proper instrumentation to meet Stat demands. These labs are designed to process large volumes of tests economically. In other words, tests are often performed in batches, with the runs scheduled to accommodate the needs of the hospital. The least expensive methods are often favored, without regard to turnaround time.

In contrast, Stat testing requires specialized attention and, often, dedicated instruments as well. The type of instrument and how it is used are pivotal determinants of how well (or poorly) a lab provides Stat service. This article will focus on the principles of selecting Stat instruments.

* Assessing needs. The first step in choosing the right instrument is to establish the framework for its operation. This involves developing a laboratory design for Stat testing, then deciding which tests to do Stat.

Several different organizational strategies can be used to develop the design. One is to integrate Stat testing into laboratory areas handling the routine workload. An advantage of this approach is that a single analyzer can handle both Stat and routine lab work; no money has to be spent on additional instruments and personnel.

On the other hand, Stat testing interrupts the normal work flow, and the single analyzer may not be well suited to Stat work. In add'ition, specimens may have to be aliquoted among different lab sections, making it harder to track down results.

Another approach is to perform Stat testing in a dedicated location. This may take the form of a Stat lab within the clinical laboratories area, a satellite lab in the hospital near a patient area requiring a high volume of emergency services, or bedside testing.

With a proper balance between instruments and personnel, the freestanding Stat laboratory can provide rapid turnaround. Management can select instruments specially designed for Stat testing instead of trying to make do with analyzers already on hand. A dedicated Stat facility is expensive to operate, however, given relatively low utilization and such fixed instrument costs as repair, maintenance, and quality control. The dedicated staff is also expensive.

Satellite Stat laboratories are often situated near operating rooms, intensive care units, or emergency rooms. Since the lab space is often difficult to obtain and limited in size, compact benchtop analyzers are an asset in these settings. The distance from the central laboratory may make supervision, staffing, and quality control a problem.

Bedside testing, the last design option, appears attractive on a theoretical level, particularly for glucose or hematocrit testing. The instruments used (hand-held devices) are much different from the sophisticated analyzers used in the other settings. The main disadvantage is that suboptimal methods, untrained operators, or a lack of quality control often lead to questionable results.

A good way to start preparing a list of Stat tests is to consult previously published lists and compare their tests to those ordered Stat in one's own institution. Each laboratory must tailor the Stat list to its own service requirements, such as the existence of an emergency room, trauma or burn center, intensive care unit, cardiac care unit, or transplant program.

Protocols should also be developed that delineate testing patterns for specific situations. These may include suspected myocardial infarction, trauma, drug overdose, or intraoperative procedures, such as a liver transplant. The laboratory should work out acceptable turnaround times with clinicians.

The next step is Stat mapping, which categorizes Stat tests by lab location and time (for example, half-hour intervals). Mapping provides an estimate of total Stat volume, individual test volumes, Stat test mix, and laboratory staffing requirements. It also lays a foundation for evaluating instruments in terms of other criteria.

* Instrument selection. Key criteria to be considered when evaluating Stat instrumentation are shown in Figure 1. The acquisition of these instruments must be viewed with the same importance as acquisition of other laboratory analyzers. Obsolete hand-medown analyzers discarded by the main lab will not get the job done in a dedicated Stat facility. The toll in maintenance, Labor, and downtime would thwart the laboratory's efforts to provide adequate service.

If a test is considered essential at any time of the day, then a Stat instrument should stand by around the clock, ready to function. Yet few instruments can operate in this mode, due to such requirements as lamp warmup time, calibration, reagent preparation, or priming. These steps can delay testing and add considerable expense if they must be taken every time an instrument starts testing from standby.

Inability to meet a 24-hour standby demand need not eliminate an instrument from consideration, however-if another analyzer is ready to perform Stat tests when the first one is unavailable. This may be accomplished with existing routine analyzers or dedicated Stat instruments.

It is often best to acquire duplicates of current laboratory instruments for dedicated Stat use. They standardize methods in the lab and insure that sequential test results can be compared whether they are performed on the routine or the Stat analyzer. Reference ranges may vary when dissimilar analyzers are used, making it difficult to interpret sequential patterns.

Of course, it may not always make sense to acquire a duplicate instrument; a less expensive alternative may suffice. In such situations, the Stat and routine analyzers can often be cross-calibrated to standardize test results.

The test menu is another important consideration in the selection of Stat instrumentation. Some laboratories may for the most part run only seven or eight different tests on the Stat analyzer, while others perform a wide variety of tests. Depending on the test volume, test types, and hours of operation, it may be desirable to consolidate all Stat work from one or several lab sections onto a single instrument.

The on-line test menu should also be evaluated in terms of the laboratory's specific needs. Although many instruments are capable of performing a broad spectrum of tests, reagents cannot always be stored on board for extended periods due to a lack of refrigeration. This may require the operator to first prepare or place reagents on the analyzer when a Stat request is received, causing a delay in testing.

Other analyzers are limited with respect to the number of reagents that can be stored on board. If many different tests are ordered, the operator will have to change reagents continually. Then there are reagents that have a shoo life span after reconstitution or that are packaged in larger amounts than the lab uses. The resulting reagent waste makes infrequently ordered tests very costly to run.

Stat turnaround time, exclusive of specimen transport and reporting, is composed predominantly of specimen processing and the specimen's instrument dwell time (the time span from sampling to test completion on the analyzer). Certain instruments reduce processing time by analyzing whole blood, thereby bypassing centrifugation. Others sample directly ftom the collection tube, eliminating the need to pour off into a cup. Such instruments offer a distinct advantage in Stat settings.

When assessing the speed with which an instrument is capable of handling Stats, it is important to determine the dwell time of a specimen on the instrument. Some dedicated Stat analyzers have dwell times of just one to two minutes versus the 10 to 15 minutes or longer that random access analyzers may require.

Each laboratory should define an acceptable dwell time for its needs. Labs with lengthy Stat turnaround times due to such external factors as specimen transport are less affected by dwell time than those where total turnaround is largely a measure of processing and dwell time.

Finally, a Stat instrument should be easy to use since it will probably be operated by technologists of varying skill levels on multiple shifts. Walkaway capability is a plus because technologists may be required to run other instruments or analyses simultaneously. Calibration and maintenance specifications should be minimal to insure that the analyzer remains operational at all times.

*Types of Stat instruments. Stat tests can be performed on virtually any type of laboratory analyzer and in the same manner as routine procedures. However, the ability to complete testing within an acceptable Stat turnaround time varies greatly from one instrument to the next.

Thus it is important to understand the general operating principles of Stat instrumentation and the applicability of each to the lab's design. Testing can generally be performed on three different types of analyzers-dedicated Stat analyzers, random access analyzers, and specimen-based profilers.

Dedicated analyzers are designed specifically for Stat use. They usually can perform up to eight or nine of the most commonly ordered tests on each specimen. Their test menu is fixed, but they can process a large number of tests per hour. Results may be available in as little as one minute, and the instruments are ready for use around the clock. This type of analyzer is well suited for a dedicated Stat facility or as a complement to routine-testing instruments in the main laboratory.

Specimen-based profilers process a set number of specimens per hour, in contrast to a random access analyzer, which processes a set number of tests per hour. A profiler's throughput varies with the number of tests ordered on each specimen.

These instruments generally have the capability to perform 2,000 to 4,000 tests per hour if all available tests are selected for each specimen. Throughput falls dramatically when only one or two tests are ordered instead of 20 or 24.

Obviously, specimen-based profilers are not appropriate in a dedicated Stat laboratory-if for no other reason, they would not fit in the limited space! In some circumstances, though, a clinical laboratory may consider using performing Stat work on this type of analyzer when it is run during the day.

Understanding the operating characteristics of specimen-based profilers is essential in determining whether Stat testing makes sense. For example, these analyzers cannot run efficiently on a 24hour standby basis and may not be available when Stat testing is needed.

In addition, placing Stat tests on some specimen-based profilers reduces overall throughput by interrupting routine runs. Reagent priming requirements can also make it relatively expensive to run a single Stat from standby. And results may not be ready for 20 minutes or more, depending on the system configuration.

As we have mentioned, virtually all random access analyzers claim Stat capability. The degree to which testing is actually performed Stat varies greatly. In general, testing can be completed faster on a random access ' analyzer than on a specimen-based profiler, but slower than on a dedicated Stat analyzer.

Several operating characteristics (in addition to those outlined earlier) should be considered when evaluating an analyzer's utility for Stat testing. These include placement of the Stat specimen, delay time to aspiration, and the test menu.

In order to process a Stat specimen, most analyzers need a mechanism to access the specimen on a priority basis. There are different ways to accomplish this.

Some instruments require that a Stat specimen be inserted into a dedicated location on the specimen tray or reaction area. If the area can only accommodate one Stat specimen but several have to be run, the operator must manually insert each specimen into the designated position instead of loading all of them together-a time-consuming process.

In contrast, other analyzers will allow placement of a Stat specimen anywhere on the routine specimen carousel. By defining that location, the analyzer can interrupt routine work to aspirate the Stat specimen, then resume routine testing where it left off. In this configuration, multiple Stat specimens can be loaded simultaneously.

The delay time to aspiration after designating a specimen as Stat is another consideration. For instance, some analyzers use laser scanners to read specimen-tube bar codes, usually at a point several positions before actual sampling. Therefore, the order of specimens after scanning cannot be changed. If a Stat specimen is inserted, the instrument may have to complete four or five specimens before aspirating the Stat. As a result there may be a delay of several minutes, depending on the specimen cycle, the number of tests ordered on each of the preceding specimens, and instrument throughput.

One advantage of most random access analyzers is their test menu, which is usually more varied than that of dedicated Stat analyzers or specimen-based profilers. This may be particularly important to Stat laboratories expected to provide a wide range of tests, including therapeutic drug monitoring and enzyme determinations.

Many analyzers can perform Stat testing. Some are dedicated instruments; others are also used for routine work. How well any of these can meet a laboratory's Stat requirements will depend upon lab design, test menu, and volume. These factors should be considered when selecting instruments.

Figure I

Criteria for selecting

Stat instrumentation

Method Duplication of current lab instruments (to standardize methods)

24-hour standby

Test menu

Ease of use

On-l ine reagent capacity

Reagent priming

Specimen dwell time on instrument

Specimen type-whole blood versus serum

Calibration

Maintenance and ease of repairs