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A protocol for verifying critical values; a few minutes more before picking up the telephone and calling in a panic value can insure that emergency therapy is really required.

Signaling an emergency, critical values often speed through to their destination like fire engines. But our hospital laboratory puts up a momentary amber light on all critically abnormal test findings.

We take time to double-check that an emergency does indeed exist before phoning an alert to the attending physician. The precaution--a verification protocol introduced along with a list of critical values in the chemistry department three in the chemistry department three years ago--usually consumes eight minutes or less. All of our laboratory departments have now adopted this approach.

Figure I shows the low and high critical values we use in chemistry. The list is posted at each instrument, telephone, and computer terminal in the lab. It covers tests with unquestionable critical limits; padding it with additional assays and vaguer limits would weaken the impact of critical value notifications. The list also excludes tests that confirm obvious clinical observations, such as neonatal bilirubins.

Verification came into play because we wanted clinicians to trust not only the limits we set but also the values we reported out as potentially life-threatening. There was more than credibility at stake: Transmitting a false critical value can be dangerous.

For example, we had once seen a neonatologist institute intravenous calcium therapy on a premature baby upon receipt of a very low Ca value. When the value turned out to be false, the physician had to turn around and treat the patient for possibly elevated calcium. The problem stemmed from the microsample, which sufficed for several tests on our multitest chemistry analyzer but ran out by the time the instrument began a calcium determination.

We did not face a life-or-death situation in that case, although an I.V. on a premature newborn always carries some risk. A specimen check could have pinpointed the problem and averted erroneous therapy. We then would have contacted the physician and requested permission to draw another specimen.

Such steps are elements of our verification procedures (Figure II). To appreciate how essential the protocol is, consider one month's reporting totals in chemistry (Figure III) at our 678-bed hospital: Out of 21,065 tests performed, 145 yielded critical values that proved valid after review, but another 91 tests yielded false critical values. In fact, roughly every other critical value was false (normal or not critical) for serum sodium, potassium, and glucose.

With the verification protocol, quality assurance doesn't get short shrift in our haste to alert clinicians. It isn't always necessary to go through all of the 10 steps of the protocol--some 80 per cent of the critical values are confirmed or explained without redrawing the patient. Once our technologists review the results, they report their findings to the supervisor or pathologist and then to the clinician.

Here's how the verification procedures work:

1. Check specimen. Checking for such abnormalities as clotting, hemolysis, and lipemia can frequently tell us if the values are valid. Clotting may produce falsely low values, while hemolysis and lipemia can lead to erroneous results for many tests, particularly electrolytes.

Perhaps the specimen was drawn with the wrong anticoagulant. Perhaps it was drawn at the wrong time: Specimens for blood glucose should not be taken more than two hours after a meal, and an arterial blood gas must be performed within 15 minutes of drawing. Sometimes simply examining the specimen for viability will immediately answer our questions.

2. Check controls. In addition to examining the specimen, we also check control values. Many times, results may be taken at face value if they lie within our assured range for an instrument or method. The range, constantly updated by computer based on quality control data, is posted at the instrument. If a result is extremely elevated, the specimen may have to be diluted to bring it back into the assured range.

3. Rerun controls and specimen. When there appears to be a problem with the control values, they are rerun along with the questionable specimen. It's also worthwhile checking that the controls were diluted properly. And when we can, we recheck the controls and specimens with a backup instrument or method. For example, we might run them on continuous flow and discrete analyzers. This can also unearth an instrument problem as the cause of erroneous results.

4. Check results on other specimens. Sometimes an intermittent problem may develop during a run of tests. This problem may not affect every specimen or be apparent during quality control. Part of the review of critical values, therefore, is a search for patterns in within-run test results.

Several specimens within the same run may intermittently show grossly abnormal values, even though controls are within limits. Many times this is caused by a clog--usually a protein buildup--or a mechanical problem. When we suspect such a problem, we run a series of six to 10 controls to determine if the instrument is malfunctioning. The instrument is adjusted if a problem exists, and specimens with questionable results are rerun.

5. Check previous values. Critical values may be consistent with a patient's earlier abnormal or critical values. Complete test histories can be recalled on laboratory computer terminals.

6. Call the nursing floor. We clal the floor for two reasons. First, we ask if a patient is undergoing any special treatment that could affect test results. If glucose, insulin, or electrolytes have been administered, for example, this information may well explain why a test result is in the critical range.

Second, getting an admitting diagnosis or current clinical picture from the floor can provide clues to the validity of critical values. We frequently consult our clinical pathologist to determine whether a particular condition or diagnosis could account for an abnormal test result.

7. Redraw the patient. If any doubt lingers about a result, we redraw the patient after obtaining the physician's permission. Thus, a technologist might occasionally suspect that the initial specimen was improperly drawn above an I.V. and that a glucose or electrolyte solution is contributing to an elevated value. Redrawing might also be necessary to make sure that an arterial specimen is indeed arterial, or that a capillary specimen from an infant is correctly drawn on ice, mixed, and immediately transported to the laboratory for blood gas analysis.

8. Test the redrawn specimen. We run follow-up specimens along with controls and compare the findings to the initial results. If they are the same, we can be reasonably sure that the questionable value was correct and report it as an accurate value. If the results are different, we report the redrawn specimen as the correct result--assuming the controls are within range and the other requirements discussed earlier are met.

9. Call attention to the problem. All double-checked critical values are reported to the department supervisor. The questionable ones are then routed to the clinical pathologist for his interpretation. The supervisor and the pathologist go over the verification process, the patient's clinical picture, quality control, and instrument operation. This systematic approach helps prevent transmission of any erroneous results to physicians.

10. Call results. This is perhaps the most important step in the critical value procedure. To benefit the patient, the values must reach the physician promptly. We lodge responsibility for notification with the technologist who discovers and verifies the abnormality. If that person cannot make the phone call, a senior technologist is assigned to do it.

Our bench technologists are more than equal to the task. All are certified and have several years' experience in clinical chemistry. A havey workload and varied patient population have made them experts in troubleshooting and verifying critical values.

We document all of the telephone calls, noting the time, the caller, and the individual contacted on both the worksheet and a list kept by the department's phone. We also make a similar notation when inputting patient data. This documentation is invaluable when the reporting system occasionally breaks down outside the laboratory.

Communication within the laboratory and the chemistry department has greatly improved as well. The daily summary of verified critical values allows each shift to keep better track of abnormal results and alerts them to watch certain patients as additional testing is done. When a new shift takes over, technologists review the daily list.

Alth ough it took a little while for the laboratory staff to adapt to the critical value procedures, our effects have produced maximum benefits. We rarely receive an irate phone call from a clinician. Quite the contrary, most of the physicians appreciate the verification program and the laboratory's concern for improving patient care. They're especially pleased with the new reliability of our blood gas results.

The chemistry department has taken the concept one step further to enhance our in-service continuing education program. As technologists do the verification, they flag any clinically interesting values and forward these results to the clinical pathologist for investigation. These cases are often used in Ce to demonstrate how different abnormal critical values are related to specific disease states.

All in all, everyone has gained a new respect for critical values, and the laboratory's credibility has soared. There's no reason why a similar approach couldn't work as well in any other lab.
COPYRIGHT 1985 Nelson Publishing
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Copyright 1985 Gale, Cengage Learning. All rights reserved.

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Author:Clevenger, Robert R.
Publication:Medical Laboratory Observer
Date:May 1, 1985
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