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Protocols for bedside testing.

Protocols for bedside testing

A wide range of tools, developed by laboratorians over the past 30 years, can help you create bedside testing quality management strategies that work for your hospital. These tools, however, must be adapted for a low-volume environment where analyses are performed sporadically by many different staff members on all shifts throughout the institution.

Since problems can arise at any stage of testing, the first step toward a quality management program is to consider which errors are most likely to occur (see Figure I). One factor may be more significant than others in your institution because of the setting or the particular test.

Policies are required to provide practical guidance about tasks associated with testing. The guidance would include precautions for the proper collection, handling, and disposal of test materials and supplies potentially contaminated with patients' blood or other specimens. Policies may also be needed to specify who is allowed to perform bedside tests and which departments will be responsible for instrument repair, periodic maintenance, and various aspects of the quality management program. It may be necessary to include criteria for such matters as staff competency to perform tests and selection of new analytic systems.

A set of written procedures establishing the standard for each analysis is an important means of achieving comparable results among operators, instruments, and patient care areas. A copy should be kept wherever the particular analysis is performed.

The procedures should clearly and succinctly explain the context and use of each test; provide instructions for patient preparation and specimen collection; describe calibration and any other checks necessary to maintain result reliability; outline the test's procedural steps; show any calculations; and include the reference or normal range as well as "action limits" that should trigger immediate notification of the primary physician. "Caution limits," requiring confirmation before therapy is changed, should also be defined.

Bedside test procedures must be written simply so that any staff member easily understands how to properly collect a specimen from an appropriately prepared patient, produce an accurate result, and provide the individual interpreting the result with adequate information to confidently make a clinical decision. A well written procedure can also be used for staff training.

We will examine several common factors that may lead to the reporting of an erroneous test result, and we will suggest remedial quality management strategies:

The patient and the specimen. Food intake close to the time of testing can obscure the steady-state level of the analyte being assayed. If hospital staff members performing bedside glucose tests don't appreciate this connection, clinicians could order a harmful change in insulin therapy.

Certain analyte determinations depend on collection of specimens at a specific time of day or at a particular interval following treatment. In therapeutic drug monitoring, for example, specimens often have to be collected at a fixed time before or after a dose. Staff members must recognize that these factors affect result interpretation and that they must document this information so physicians can be sure the drug levels are interpretable.

Written procedures should prominently display guidelines on recording the time of the most recent food intake or drug dose. The procedures should also cover possible problems with patient preparation and timing draws.

Specimen collection techniques also affect result reliability. A delay in processing a blood specimen can yield an erroneous prothrombin time. Milking a heel or fingerstick to obtain an "adequate" specimen, or prolonged use of a tourniquet, can lead to questionable results for glucose, potassium, hemoglobin, and hematocrit determinations, among others.

Transportation and storage, frequent sources of problems in a hospital's central laboratory, occasionally cause problems in bedside testing. For example, if a staff member delays testing to deal with another patient care matter, the effect of environmental temperature or humidity on the specimen may alter the eventual result.

Collection of a specimen in some cases, such as for measurement of fetal scalp vein pH determinations, is exceedingly difficult and prolonged. This can, in turn, increase the likelihood of clotting and interference with transfer of the specimen to the testing system, which would produce an erroneous result.

Bubbles in some collection or transfer devices affect the volume of specimen metered into the analytic system. Exposing blood gas specimens to room air changes the partial pressures of the gases and distorts test results.

It is difficult to detect such inaccuracies --which tend to be random rather than systematic errors --with day-to-day quality control procedures. Consequently, if a particular determination is prone to such problems, operator training programs must emphasize their impact and how to avoid trouble.

Certain specimen-related issues are complex and require clearly posted guidelines to insure proper collection and storage. Staff members performing some bedside testing need to be sure the specimen is satisfactory. Specimen rejection criteria must be clearly defined, leaving little room for staff judgment calls. This is particularly critical to insure the reliability of cytological and microbiological test data.

To reinforce the importance of following specimen-related guidelines, the staff must be made aware of the potential inaccuracy of results produced with an unsatisfactory specimen. Specimen-related issues should be incorporated into the operator training program and the written procedures.

The operator. With most bedside test systems, operators must correctly perform some activities or functions that are critical to result reliability. This may mean transferring a small measured amount of specimen to the system or preparing the system prior to processing specimens.

A hospital may want to document an operator's proficiency before allowing him or her to perform bedside tests. Some hospitals are developing programs to check the current competency of all certified personnel by periodically asking them to test samples whose analyte concentration has been predetermined in the laboratory. If an operator's results show excessive variation, feedback and retesting should take place until performance reaches an acceptable level.

The procedural steps used in different bedside test systems are often similar but not identical, so staff members cannot apply the exact same technique everywhere. Since nurses may work in more than one area of the hospital, or in more than one hospital, they need to know that apparently trivial changes in the way they perform tests can affect result reliability.

For example, they must always follow manufacturer instructions on the type of material to use for removing excess blood from a reagent strip. The wrong material, such as a paper towel instead of a cotton ball, may alter the reflective characteristics of some reagent strips or result in incomplete blood removal, leading to erroneous results. Inability to accurately time one or more critical steps is another operator deficiency that can skew bedside results, such as glucose data.

A competency testing program will pick up some of these errors. The operator training program can emphasize the importance of strict adherence to the standard testing procedure.

Interrupting the analytic process also increases result variability and the possibility of producing erroneous data. Nurses often must stop working on a bedside test to attend to their primary patient care duties, even if the test takes only 60 to 180 seconds.

In one system, the results are almost sure to be erroneous when there's a delay in closing the specimen tray after applying the specimen to the reagent strip. It is possible to minimize the consequences of interruptions with systems that limit the number of critical steps. However, even these systems may be subject to increased variability or inaccuracy because of a break in the analytic process.

Reagents and instruments. Multiple lots of a reagent are frequently found on a single patient care unit. Adjustments must be made in the test system to compensate for lot-to-lot variability in reagent activity and insure comparable results.

Systems built into some instruments automatically monitor the current reagent lot. On instruments lacking such systems, erroneous results may occur when an operator enters the wrong lot parameters. It is best in distributed testing to use instruments that do not depend on entering a code or otherwise identifying the reagent lot being used. If that's not possible, the written procedure should stress the importance of entering correct lot information.

Although most test systems employ single-use reagent packets, reagents for a sizable number of systems are packaged in bulk rather than wrapped individually. These reagents may be prematurely inactivated by improper storage temperature or excessive exposure to moisture or high humidity. Reconstitution errors, when more technically demanding systems are used in bedside testing, can also mar results.

Such factors should be considered in selection of bedside test systems. In addition, a day-to-day quality control program can alert an operator to premature reagent deterioration or reconstitution errors.

While bedside test systems are usually calibrated at the factory, the operator may have to make periodic checks, for an instrument that otherwise is functioning normally may still produce unreliable results. Similarly, in battery-operated instruments, the loss of the charge may impede normal use.

If the manufacturer recommends periodic calibration, a laboratory staff member with adequate instrument maintenance background should be responsible for deciding when a system is ready to go into service. The lab can also take responsibility for cross-checking the comparability of results produced with new reagent lots.

Frequently, a bedside test system will seem to be insensitive to specimen volume changes when, in fact, it does have critical volume limits. Some systems can alert the operator to errors in specimen volume, but many others cannot. Use of an inappropriate specimen--capillary versus venous, or whole blood versus serum, for example--leads to erroneous results with some systems.

Unfortunately, these issues will probably come to light only when discrepancies are noted between bedside and laboratory data. This is an important reason to periodically compare results produced in the laboratory and at the bedside with specimens collected at the same time.

Periodic maintenance and repair. Staff members who run bedside tests could be trained to perform simple maintenance, but it is likely that they will have neither the time nor the inclination to do it well. It is imperative, therefore, that the laboratory or the hospital's instrument service section develop protocols for periodic maintenance of each bedside instrument. Figure II shows problems that can afflict two types of bedside test systems.

A centralized master instrument log forms a record of each instrument's maintenance and repairs and indicates when routine maintenance is due again. Since bedside test systems tend to be low in cost, a hospital might opt to buy additional units as temporary replacements for instruments requiring periodic maintenance or repairs. Management responsibility for instrument maintenance and repair should be assigned to a group that has the interest, understanding, and competence to get the job done.

Quality control, data reduction, and interpretation. Most clinical laboratories validate on a day-to-day basis that their systems are functioning properly and that results produced on them can be used with confidence. Such validation can be much more complex for bedside testing because a large number of people are involved and they do not fully appreciate the importance of this activity.

Most current test systems produce quality control data that are useful to technologists monitoring the systems' functionality but are not easily understood by bedside testing personnel. Simplified guidelines with preset limits can help bedside personnel determine whether quality control results indicate a test system is running properly. Otherwise, such decisions would have to be centralized and made after the fact. Quality control problems then encountered would, until investigated, cast doubt on results already used in patient care decisions.

On the other hand, it is possible to centralize the use of quality control data to monitor analytic systems for trends that suggest impending failure. This more sophisticated surveillance can be performed periodically by a laboratory staff member looking for trends or shifts in graphed QC data. If the instrument is capable of storing and downloading competency testing information and patient care results, it should be relatively easy to develop a complete instrument log that includes all the relevant quality management data in a single report.

The report. Half of all laboratory errors are clerical rather than the result of instrument, reagent, or testing failures. A physician assumes that the reported result was transcribed correctly, that it comes from a specimen collected from the specified patient, and that the time and date of specimen collection are correctly shown. One consideration in selecting a system for use at bedside is the nature of the reporting mechanism --a printed report is preferable to display of the result on the face of the instrument.

The system for capturing results should be simple and fit into the pattern of similar systems used elsewhere in the hospital. Since the staff members in patient care areas are already accustomed to filling out charge slips for items distributed by central supply or the pharmacy, they should have no problem entering the test result, operator code, and the time and date on the charge/report slip. This would enable the laboratory to log the results into its information system.

Such an approach also allows the lab to monitor the result capture rate, since the number of reagent packets distributed is easily determined. Moreover, the system can be used to monitor competency testing and daily quality control testing if the patient care units send a charge/report slip with these results to the lab for logging and analysis.

Documenting the timeliness, accuracy, and readability of the report of test results is a fundamental laboratory practice. Since bedside test results are often used to make treatment decisions, it is important to enter this information into the patient's record in an orderly, predictable, and reliable manner. We believe that all laboratory data pertinent to the patient's care should appear in the same section of the record.

Because of variable precision or accuracy, it may be necessary to assign differnt test names to results produced for the same constituent by different methods. A quality management program should minimize the differences between such results, regardless of where testing is performed.

Some institutions carry bedside test results in a separate section of the medical record or on special bedside testing forms kept with the vital sign sheets at bedside. If this approach is selected, it is important to incorporate all information used in making patient care decisions into the medical record at the time of discharge so that any subsequent questions about a patient's care can easily be resolved. Incomplete record keeping can seriously impair an institution's ability to defend itself against a malpractice suit.

Action values and criteria for lab retesting. If a bedside test result is markedly abnormal, holding up the report could delay diagnostic or therapeutic intervention and compromise the care of a seriously ill patient. In contrast to their grasp of other aspects of testing, bedside personnel are usually equipped to recognize when a clinically significant change in values has occurred. They are thus likely to promptly notify the responsible physician.

Nonetheless, it is important to define for each bedside test the result limits that dictate immediate notification. These limits can be expressed as a relative change in value for some tests or as fixed preset values for others. Whenever results are communicated verbally, it is wise to note the time and date of the contact on the written report, the person spoken to, and the information transmitted.

Results that change abruptly are another concern. Do they represent a change in the patient or changes in the analytic system? Personnel performing bedside tests need to understand that either can happen and that repeat testing or confirmation by the central laboratory will occasionally be necessary.

Some hospitals also confirm a fraction of routine bedside results with analyses in their clinical laboratory. It is best to do such routine checks in conjunction with clinically necessary testing. If a specimen is drawn for clinical laboratory analysis, it can also be tested at bedside, and the results of both procedures logged to document day-to-day comparability and to provide a basis for investigating any developing differences.

Infectious hazards. The current heightened danger of infections acquired from contact with patients' blood and blood products makes it especially important that those performing bedside tests know how to protect themselves. They should wear latex or plastic gloves when collecting specimens and performing analyses. Disposal of potentially contaminated waste should also be part of any bedside quality management program.

Although sensitized to their personal risk, the bedside staff may not recognize the risk that discarded serum or reagent packs or other parts of the testing system can pose to fellow hospital workers. Setting up a testing station with all the necessary instructions, reagents, instruments, and disposal containers can minimize the possibility that potential infectious materials might inadvertently reach individuals who are not aware of the danger.

The concluding article in this series will appear in next month's issue of MLO.

Photo: Figure I Things that can go wrong with bedside testing

Photo: Figure II Bedside test system problems that can distort results
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Copyright 1988 Gale, Cengage Learning. All rights reserved.

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Title Annotation:part 2
Author:Belsey, Richard; Baer, Daniel M.
Publication:Medical Laboratory Observer
Date:Mar 1, 1988
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