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Within-Individual Mean Corpuscular Volume Variation.

To the Editor.--We read with interest "Biological Variations of Hematologic Parameters Determined by UniCel DxH 800 Hematology Analyzer." (1) Most of the estimates of biologic variation of the common analytes reported by Zhang et al (1) were close to previously reported literature values. We are puzzled, however, about the broad intraindividual variation for mean corpuscular volume (MCV; 1.12%). Although compilations of biologic variation published before 2000 indicated intraindividual MCV coefficients of variation (CVs) could exceed 1%, 2 recent studies determined the CV was much lower, either 0.18%2 or 0.34%. (3) As a result, the Zhang et al reference change values for MCV are much higher than our intuitive reference change values (perhaps, 2 fL) when we examine sequential patient MCVs measured by analyzers that are much older than the analyzer used by Zhang et al.

The larger intraindividual MCV CVs reported before 2000 were likely associated with the use of more-imprecise instrumentation. Today, our analytic variations in MCV measurements are miniscule. (4) Reasons for a tripling or quadrupling of the estimated intraindividual CV might include the incorporation of some outlying data, analyzer noise, or even some unusual individual-specific variation. We are wondering if Zhang et al would reexamine their MCV data and correlate any available quality control results with those data. Could this variation have been due to some sporadic instrument or individual source?

GEORGE CEMBROWSKI, MD, PhD

Department of Laboratory Medicine and Pathology

University of Alberta Hospital

Edmonton, AB T5N 3M7

Canada

KAILA TOPPING, MD

Department of Laboratory Medicine and Pathology

University of Alberta Hospital

Health Sciences Centre

Edmonton, AB T6G 2B7

Canada

GWEN CLARKE, MD

Department of Transfusion Medicine

Dynacare Kasper Medical Laboratories

Edmonton, AB T5J 5E2

Canada

References

(1.) Zhang P, Tang H, Chen K, Chen Y, Xu D. Biological variations of hematologic parameters determined by UniCel DxH 800 hematology analyzer. Arch Pathol Lab Med. 2013; 137(8): 1106-1110.

(2.) Sennels HP, Jorgensen HL, Hansen AS, Goetze JP, Fahrenkrug J. Diurnal variation of hematology parameters in healthy young males: the Bispebjerg study of diurnal variations. Scand J Clin Lab Invest. 2011; 71(7):532-541.

(3.) Lacher DA, Barletta J, Hughes JP. Biological variation of hematology tests based on the 1999-2002 National Health and Nutrition Examination Survey. Natl Health Stat Report. 2012; 12(54):110.

(4.) Cembrowski GS, Smith B, Tung D. Rationale for using insensitive quality control rules for today's hematology analyzers. Int J Lab Hematol. 2012; 32(6, pt 2):606-615.

doi: 10.5858/arpa.2013-0685-LE

In Reply.--We thank Drs Cembrowski, Topping, and Clarke for their interest in our article. (1) Regarding the concern about broad mean corpuscular volume (MCV) intraindividual biologic variation (CVi), we have reexamined our MCV data. No obvious outliers were identified. Therefore, our MCV results represent all data points investigated. in addition, all available quality control results were within acceptable ranges.

We do not know exactly why our CVi results for MCV are greater than those from two recent studies mentioned. (2,3) The likely explanations may include the differences in study design, study duration, data points taken, numbers of individuals included in the study, and a different ethnic population, which may introduce some unusual individual specific variations. We also could not exclude the possibility of some sporadic or random instrument imprecision during sample analysis. interestingly, in Sennels et al, (2) the analytic within-run variation for MCV is greater than biologic within-subject variation (0.6% versus 0.18%).

We agree that the analytic variations for MCV from current hematology analyzers are small, and the evidence from our study also demonstrated that analytic variation for MCV was 0.1%, which is comparable with those variations from most modern hematology analyzers (ranging from 0.78% to [less than or equal to]1%). (4)

DONGSHENG XU, MD, PhD

CBLPath Inc

Rye Brook, NY

HUQIANG TANG, MS, MPH

Clinical Laboratory Center

The Second Affiliated Hospital

Zhejiang university School of Medicine

Zhejiang, China

References

(1.) Zhang P, Tang H, Chen K, Chen Y, Xu D. Biological variations of hematologic parameters determined by UniCel DxH 800 hematology analyzer. Arch Pathol Lab Med. 2013; 137(8): 1106-1110.

(2.) Sennels HP, Jorgensen HL, Hansen AS, Goetze JP, Fahrenkrug J. Diurnal variation of hematology parameters in healthy young males: the Bispebjerg study of diurnal variations. Scand J Clin Lab Invest. 2011; 71(7):532-541.

(3.) Lacher DA, Barletta J, Hughes JP. Biological variation of hematology tests based on the 1999-2002 National Health and Nutrition Examination Survey. Natl Health Stat Report. 2012; (54):1-10.

(4.) Hematology analyzers: product guide. CAP Today. 2013; 27(12):12-22.

doi: 10.5858/arpa.2014-0011-LE
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Title Annotation:Letters to the Editor
Author:Cembrowski, George; Topping, Kaila; Clarke, Gwen
Publication:Archives of Pathology & Laboratory Medicine
Article Type:Letter to the editor
Date:Oct 1, 2014
Words:764
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