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'Diff/if': a differential policy that works.

`Diff/if': A differential policy that works

Cutting the number of diffs in half has saved the authors' many branch labs time and money without sacrificing quality.

Health care financing is just as constrained in Canada, where we work, as in the United States. Here, too, attention has increasingly focused on achieving the best use of laboratory services as a way to control costs.

When our hematology department underwent a no-nonsense fiscal review several years ago, the routine white blood cell differential quickly surfaced as one of the section's least cost-effective tests. Accordingly, we assessed the situation and decided to introduce a policy we called "morphology--diff/if." The results have been gratifying.

Our technologists now perform diffs only when indicated by strict clinical criteria. Implementing the new policy immediately cut the number of differentials by 50 per cent and greatly improved both the efficiency and the balance sheet of the laboratory. * Rationale. Studies have repeatedly revealed three characteristics of differentials that came into play in our deliberations: They are labor intensive and nonspecific and have minimal clinical value in routine screening and diagnosis.(1-3) One 1986 report suggested that the WBC differential adds little clinically relevant information in the acute-care setting of the emergency room.(4) Such findings caused the British Columbia Association of Laboratory Physicians to formulate policies to reduce the use of diffs in the interest of curbing unnecessary testing and controlling health care costs.

Well aware of this trend, the administrators of Island Medical Laboratories began to ponder the problem in earnest during the summer of 1987. Our group of 24 laboratories, which employs about 250 people, provides predominantly outpatient services for the approximately 500,000 residents of Vancouver Island, British Columbia. We have two major full-service labs and 22 branches on the island, which is roughly the size of Great Britain. The branches include satellite labs and collecting stations. Some 25 technologists process about 110,000 hematology profiles each year.

Taking our cue from the government's interest in restricting diffs, we scoured the literature to see whether such a policy was warranted for our particular population of ambulatory patients. We learned that when the hematology profile (hemoglobin, WBC, RBC indices, and platelet count) falls within normal limits, chances are slim that either a white cell diff or red cell morphology will reveal any clinically significant abnormality.(5,6) We therefore decided to stop doing differentials when a patient's white cell count and hematology profile were normal. This and many other thoughtful decisions made their way into the successful protocol we slowly developed (see Figure I).

A widely accepted but underinvestigated dictum holds that the very young and the very old may have a clinically significant leftshifted diff without demonstrating absolute leukocytosis.(7) Realizing that this observation deserved further study, but seemed to have merit, we decided to continue to do diffs ordered by physicians for all patients younger than 12 and those older than 65, regardless of the total white cell count.

Since then, we have performed a two-month review of 733 elderly ambulatory patients tested by our labs. Results indicate that when a patient's screening hematology profile is normal, the likelihood that further testing will identify a clinically significant abnormality is virtually nil.(8) Before changing our protocol in this respect, we'll await feedback from our physicians and others after our study has been published.

Certain patients get a diff regardless of the initial white cell count: those treated at the cancer clinic, because of the chemotherapy they receive; those under the care of a rheumatologist, because they may be taking gold or immunosuppressive drugs; and those referred to or currently consulting a hematologist or oncologist.

Technologists run a routine diff whenever a doctor orders an absolute eosinophil count--mild eosinophilia can be present in the absence of overall leukocytosis. Physicians often order a differential when screening for allergies, parasites, or a drug reaction.

Differentials are performed automatically with tests ordered for mononucleosis, particularly those with negative results. Our reasoning was that an order for a mono test reflects a high index of suspicion of mono-like illness. Even when the total white cell count is normal, finding variant or atypical lymphocytes can provide collaborative evidence of another viral illness, such as cytomegalovirus infection or hepatitis. * Delegating decisions. Following the lead of other investigators,(9) we decided to have technologists initially perform a scan of the WBC distribution and red cell morphology when a specimen exceeds the limits set for the other hematology parameters. The technologist then makes a judgment call concerning the need for a follow-up differential.

If a physician calls to order a diff, technologists honor the request even if criteria indicate that it is not warranted. When a doctor merely notes a request on the lab slip, the technologist may forgo the diff if other results are normal.

This approach affords a considerable saving of labor at the bench. An average scan consumes just 5 CAP workload recording units, as compared with the 11 workload units necessary to complete a 100-cell differential.

Our diff/if policy includes criteria for doing follow-up differentials if a patient's parameters demonstrate a significant shift. Canadian labs are required by law to keep a copy of all lab test results on file for one year. Technologists routinely check the files when test orders arrive--a manual task we hope to computerize soon. * Spreading the word. As we developed final formulations for our protocol in the fall of 1987, we shifted our focus to education. The success of the diff/if policy, we knew, would depend on the cooperation of technologists and physicians. First, we'd have to teach the technologists at our satellite locations how to scan blood films with a 10-power objective. Then--the hard part, we feared--we would have to wean physicians from their reliance on diffs.

The technologists were old hands at doing diffs, of course, but many were unfamiliar with the scanning technique. The chief technologist for all the labs produced a 20-minute video to rectify this procedural shortcoming. She then took her show on the road, visiting each branch that processed labwork. (The collecting stations were bypassed.) After screening the video, she worked with technologists individually, reviewing slides until they felt comfortable with their prowess.

During this process, the chief technologist did a lot of talking--and listening--to ease technologists' anxiety over the upcoming major change in procedure. She stressed, for example, that the differentials they would no longer perform would be routine specimens, not the more interesting abnormals. She explained that the policy would encourage laboratorians to use their analytical and technical skills: After scanning, the technologist would decide whether to proceed with a diff.

While the site visits were going on, we sent a letter to the approximately 500 referring physicians in our service area. The letter outlined the protocol and asked for feedback. The Island Medical physicians' group followed up by organizing rounds at hospitals and through the local medical society. Our strategy--to reach physicians on their home ground--paid off. Once the doctors knew what to expect, they were much more likely to cooperate.

Acceptance in the lab was crucial to the policy's smooth implementation and optimum compliance. We laid the groundwork early by making a sincere request for suggestions from the technologists and then following through on their many excellent ideas. In retrospect, we can say that all 25 technologists involved in hematology at the main and branch labs helped set the policy.

The process was less unwieldy and time consuming than we had predicted. The computer network that links our labs was a tremendous help. We sent out the first draft via computer, incorporated technologists' suggestions, and then distributed a revised version. Each time we added a protocol, we repeated the process until everyone was satisfied--an exchange that took place three or four times over the course of two months. The resulting team spirit eased technologists' qualms and gave them that extra bit of courage to suggest to a doctor that no differential was necessary. * Plan in effect. After six months of planning, formulating, revising, and educating, the policy went into force in February 1988. Our client physicians, to their credit, rallied to the cause. The dreaded deluge of complaints and cranky calls never materialized.

The benefits were immediate. Diffs dropped by 50 per cent in all labs. Although blood film scans increased by 33 per cent across the board, the lab still gained ground, since scanning is far less labor intensive and far more economical than differentials.

The staff quickly adjusted to the system they had helped devise. The physicians understood why they needed to do their part in the interest of cost containment under Canada's global health care budgeting plan. Although our labs still receive calls from concerned clinicians asking why a diff won't be done, the policy's built-in safety mechanism allays their fears. Once doctors realize they can order a diff simply by calling the technologist or supervisor, they usually calm down. Indeed, the number of unnecessary differentials requested is small.

Our educational efforts continue via the lab group's newsletter for physicians. Since it's mailed to all medical offices in our service area, it reaches both current and prospective clients. The newsletter is a good public relations tool that gives us opportunities to keep our clients informed about changes in the protocol.

More and more, hematology technology is done on automated differential instruments that provide three- or five-part diffs as part of the routine profile.(10) Yes, we do have such instruments in some of our labs; but they are expensive, and smaller laboratories can get along fine without them. Furthermore, even the most sophisticated instrument cannot provide an accurate assessment of red cell morphology on its own.

The morphology--diff/if policy bridges such gaps. Because we'll all have to make hard choices as health care dollars become more and more limited, we must consider any viable alternative to lab overutilization. By following the diff/if policy, our labs are cutting health care costs without sacrificing the quality of care.

(1)Connelly, D.P.; McClain, M.P.; Crowson, T.W.; et al. The use of the differential leukocyte count for inpatient case finding. Hum. Pathol. 13:294--300, 1982. (2)Rich, E.C.; Crowson, T.W.; and Connelly, D.P. Effectiveness of differential leukocyte count in case finding in the ambulatory care setting. JAMA 249:633--636, 1983. (3)Shapiro, M.F., and Greenfield, S. CBC and leukocyte differential count: When are they needed? Ann. Intern. Med. 106:65--74, 1987. (4)Wenz, B.; Gennis, P.; Canova, C.; et al. The clinical utility of the leukocyte differential in emergency medicine. Am. J. Clin. Pathol. 86:298--303, 1986. (5)Burry, A.F.; Robinson, L.G.; and Perel, I.D. Cutting corners in hematology. Med. J. Aust. 1: 982--984, 1972. (6)McNeely, B., and Boyko, W. An evaluation of the automated multichannel blood count for hematologic case finding on elective hospital admission. Clin. Biochem. 17:215, 1984. (7)Mathy, K.A., and Koepke, J.A. The clinical usefulness of segmented vs. stab neutrophil criteria for differential leukocyte counts. Am. J. Clin. Pathol. 61:947--958, 1974. (8)Brigden, M.L., and Page, N.E. The lack of clinical utility of white blood cell differential counts in elderly individuals with normal hematology profiles. Arch. Pathol. Lab. Med. (in press) (9)Arkin, C.F.; Medeiros, L.J.; Pevzner, L.Z.; et al. The white blood cell differential: Evaluation of rapid impression scanning versus the routine manual count. Am. J. Clin. Pathol. 87:628--632, 1987. (10)Pierre, R.V. The routine differential leukocyte count vs. automated differential counts. Blood Cells 11:11--23, 1985.

Malcolm L. Brigden, M.D.; Ethel V. Preece, RT; and Norma E. Page, RT The authors are, respectively, head of hematology, chief technologist, and research and development technologist at Island Medical Laboratories, Victoria, B.C., Canada.
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Author:Brigden, Malcolm L.; Preece, Ethel V.; Page, Norma E.
Publication:Medical Laboratory Observer
Date:Mar 1, 1990
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