Q & A Column, 9/14

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1. Renbourn ET. Variation, diurnal and over longer periods of time, in blood haemoglobin, haematocrit, plasma protein, erythrocyte sedimentation rate, and blood chloride. J Hyg (Lond). 1947;45(4):455–467.
2. Sennels HP, Jørgensen HL, Hansen AS, et al. Diurnal variation of hematology parameters in healthy young males: the Bispebjerg study of diurnal variations. Scand J Clin Lab Invest. 2011;71:532–541.
3. Schumacher YO, Wenning M, Robinson N, et al. Diurnal and exercise-related variability of haemoglobin and reticulocytes in athletes. Int J Sports Med. 2010;31(4):225–230.
4. Jacob G, Raj SR, Ketch T, et al. Postural pseudoanemia: posture-dependent change in hematocrit. Mayo Clin Proc. 2005;80(5):611–614.

Tracy I. George, MD, Associate Professor of Pathology,
Chief, Hematopathology Division, Director, Hematopathology Fellowship
University of New Mexico Health, Sciences Center, Albuquerque
Member, CAP Council on Scientific Affairs and Quality Practices Committee

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Q. We would like to standardize reference ranges throughout our system of regional facilities, using our main laboratory to establish the ranges. How does the CAP view using the transference process as described in CLSI document C28-A3C, Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Guideline? Is this an approved method for establishing reference ranges? Is it an acceptable process once the laboratory director approves it?

A. CAP Laboratory Accreditation Program checklist requirement COM.50000, Reference Intervals Established/Verified, says “The laboratory establishes or verifies its reference intervals (normal values).” The CAP does not give preference for one method over another but would fully support the practice of transference, as we will describe here.

The goal of having standard reference intervals throughout a regional health care system is laudable. To achieve this goal, there are two critical prerequisites: The facilities must have comparable patient populations, and the assays they use must generate comparable values.

In the situation described, the plan is to establish reference intervals at the main laboratory and then have the other facilities adopt those intervals as their own. According to CLSI EP28-A3C (formerly C28-A3C), this is exactly the situation in which one would use “transference.” Each facility would compare its method to the main laboratory’s method by performing correlation studies using fresh patient samples. Of note, the samples used in these studies can come from any patients; they do not need to come from reference individuals. If the values between the two methods match, the regional facility can adopt the main laboratory’s proposed reference intervals. If the values do not match, then the regional facility, before adopting the proposed reference intervals, would have to incorporate slope and intercept changes in its method to make the values match. (This entire exercise, of course, is straightforward if the regional facilities are all using the same method as the main laboratory; one would fully expect the correlation studies to yield matching results.)

As noted in EP28-A3C, it is always a good idea, as a final step, to verify the proposed new reference intervals by collecting samples from 20 reference individuals at each facility and ensuring that no more than two of those values, for each analyte, are outside the proposed limits. If your institution is able to confirm the reference interval arrived at by transference in this fashion, it would represent exemplary performance.

1. College of American Pathologists Laboratory Accreditation Program All Common Checklist, April 21, 2014.
2. EP28-A3C—Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory; Approved Guideline—Third Edition. Wayne, Pa.: Clinical and Laboratory Standards Institute; 2010.

Gary Horowitz, MD, Medical Director, Clinical Chemistry,
Beth Israel Deaconess Medical Center
Associate Professor of Pathology, Harvard Medical School, Boston
Chair, CAP Chemistry Resource Committee

David Alter, MD, DABCC, Clinical/Chemical Pathologist
Michigan Pathology Specialists
Spectrum Health Regional Laboratory, Grand Rapids, Mich.
Vice Chair, CAP Chemistry Resource Committee

Dr. Kiechle is medical director of clini­cal pathology, Memorial Healthcare, Hollywood, Fla. Use the reader service card to submit your inquiries, or address them to Sherrie Rice, CAP TODAY, 325 Wau­ke­gan Road, Northfield, IL 60093; srice@cap.org.