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Primary care
Users beware! Biological variation in complete blood counts over short time intervals
  1. Andrea DeLuca1,
  2. Joshua Betz2,
  3. Robert Bollinger3,
  4. Stuart Ray3,
  5. Yukari Manabe3
  1. 1 Department of Health Policy and Management, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
  2. 2 Department of Biostatistics, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
  3. 3 Johns Hopkins School of Medicine, Baltimore, Maryland, USA
  1. Correspondence to Andrea DeLuca, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21231, USA; adeluca{at}

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A complete blood count (CBC) is the most commonly ordered laboratory test for patient diagnosis and treatment.1 Clinical decisions are often made on the basis of a single result which is rarely repeated. The availability of more rapid tests for CBCs that are accessible and approved for Clinical Laboratory Improvement Amendments (CLIA)-waived use at the point of need increases the likelihood that serial testing may occur over short periods of time.2 Understanding natural CBC variation in healthy individuals may help clinicians interpret serial test results which may have a range of values.


We sought to evaluate CBCs from blood drawn over a short time period and assessed in separate, accredited labs to understand biological and laboratory-based variability.

Methods and findings

Ten healthy adult volunteers with a self-report of being healthy were recruited by a study nurse and signed informed consent between April and May 2017. At baseline, 1 hour and 2 hours, six 3 mL tubes were drawn each time and sent as routine tests in duplicate to three College of American Pathologist certified clinical core laboratories for CBC: Lab 1 used a Beckman Coulter LH750 (Beckman Coulter, Atlanta, GA), Lab 2 used a Sysmex XE2100 (Sysmex America, Lincolnshire, IL) and Lab 3 used a Sysmex XN9000 (Sysmex America). The total time range covered by this study was 120 min, consistent …

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  • Contributors AD and YM drafted the manuscript. JB analysed the data. AD, YM, JB, SR and RB all provided critical input on the final version of the manuscript.

  • Funding Funding for the study described in this publication was provided by miDiagnostics. miDiagnostics is a private company created to develop a point-of-need diagnostic platform.

  • Competing interests Johns Hopkins University holds a Board of Directors position in miDiagnostics, owns equity in the company and is also eligible to receive royalty payments for commercial sales by miDiagnostics. AD, JB, RB, SR and YM are eligible to receive distributions of royalty payments to JHU and/or payments related to JHU equity ownership interests in miDiagnostics. This arrangement has been reviewed and approved by the Johns Hopkins University in accordance with its conflict of interest policies.

  • Ethics approval Johns Hopkins Medicine Institutional Review Board (approval number: IRB00122523).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement There are no additional data beyond what is included in our original analysis.

  • Patient consent for publication Not required.