Conexiant
Login
  • The Analytical Scientist
  • The Cannabis Scientist
  • The Medicine Maker
  • The Ophthalmologist
  • The Pathologist
  • The Traditional Scientist
The Pathologist
  • Explore Pathology

    Explore

    • Latest
    • Insights
    • Case Studies
    • Opinion & Personal Narratives
    • Research & Innovations
    • Product Profiles

    Featured Topics

    • Molecular Pathology
    • Infectious Disease
    • Digital Pathology

    Issues

    • Latest Issue
    • Archive
  • Subspecialties
    • Oncology
    • Histology
    • Cytology
    • Hematology
    • Endocrinology
    • Neurology
    • Microbiology & Immunology
    • Forensics
    • Pathologists' Assistants
  • Training & Education

    Career Development

    • Professional Development
    • Career Pathways
    • Workforce Trends

    Educational Resources

    • Guidelines & Recommendations
    • App Notes

    Events

    • Webinars
    • Live Events
  • Events
    • Live Events
    • Webinars
  • Profiles & Community

    People & Profiles

    • Power List
    • Voices in the Community
    • Authors & Contributors
  • Multimedia
    • Video
    • Podcasts
Subscribe
Subscribe

False

The Pathologist / Issues / 2016 / Mar / Variations on a Drop
Hematology Hematology Cytology Point of care testing Training and education

Variations on a Drop

James’ landmark paper: MM Bond, RR Richards-Kortum, “Drop-to-drop variation in the cellular components of fingerprick blood”, Am J Clin Pathol, 144, 885–894 (2015). PMID: 26572995.

By James Nichols, Ian Cree, Miguel Reyes-Múgica 03/29/2016 1 min read

Share

This manuscript describes the variability of complete blood count (CBC) results in a fingerstick capillary sample. It was an initial pilot study, but the results have ramifications for the reliability of point-of-care testing devices that use capillary blood samples. Although the paper only looked at CBC and hemoglobin, anything that provides a quantitative value – glucose meters, coagulation devices, serology, disease markers and more – can be tested by fingerstick, so all of these tests may be subject to the variability the authors observed. It’s been known for some time that glucose meters often give different results with capillary samples than with venous samples. But even between capillary samples, there’s variation. Some of this is due to operator technique; people who squeeze the finger to get enough blood for the device end up contaminating the sample with interstitial fluid and other non-blood substances. It’s even more of a problem when you are sampling for coagulation tests or other devices. But I think this paper is interesting because it looks at standard blood samples by fingerstick – no difficult draws or unusual sampling methods – and determines that there is variability even within a single drop of blood. As a pilot analysis, it’s quite in-depth. The authors looked at multiple samples from 11 different donors. In practice, though, I wouldn’t recommend the use of multiple fingerstick collection from the same patient – it increases the time and expense of testing. It’s useful for method validations – examining the variability we see with a particular sample type and looking at reproducibility with different patients and operators. Part of the advantage of point-of-care testing is its speed, and the ability to take action on the spot. If you have to run three tests from three different fingersticks on same patient, wait for the results, and then average them, you delay the intervention.

A possible limitation of the paper is that the authors needed to dilute the samples, because they weren’t able to collect sufficient amounts of blood for cell counts on a larger automated hematology analyzer. That dilution step could add variability to the test results. To mitigate its effects, the authors also used a HemoCue device to analyze hemoglobin. This analyzer only requires 5 μL of sample, so there’s no need for dilution, and it showed similar variability to the larger hematology analyzer in different portions of the fingerstick blood samples. I don’t think there’s any way of overcoming the issue of variability while maintaining small sample sizes – but I also don’t think we should stop taking small samples. It doesn’t preclude the use of capillary sample tests; it’s just something we should be aware of as we perform the tests, like any other limitation or source of variation. We’ll consider it as we educate our operators, too; we have nearly 6,000 operators doing glucose testing, and we’ll want them to be aware of their sampling technique and try to minimize variation.

It will be interesting to see if similar variability is seen in portions of a blood drop for other common point-of-care tests, like glucose, hemoglobin A1c, coagulation or chemistries (like sodium, potassium, creatinine and even cardiac markers). As technologies become more sensitive – using smaller and smaller sample sizes to detect increasingly minor changes – I expect that variability will be a continuing problem. It’s a good opportunity for engineers and designers to collaborate with the end-users of the instruments to figure out ways to minimize its effect. In the future, we might even find that certain technologies are more prone to these effects than others, on the basis of sample volume or sampling technique. That may help us to steer more towards those technologies that are less dependent on variability within the drop.

Variations on a Drop by James Nichols

A Paper to Circulate by Ian Cree

Hyperspectral Disease Diagnosis by Peter Griffiths

Diagnosis: Digital by Liron Pantanowitz

Collagen and the Colon by Miguel Reyes-Múgica

Newsletters

Receive the latest pathology news, personalities, education, and career development – weekly to your inbox.

Newsletter Signup Image

About the Author(s)

James Nichols

James Nichols is Director of Clinical Chemistry and Professor in the Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, USA

More Articles by James Nichols

Ian Cree

Ian Cree is Head of the World Health Organization Classification of Tumors Group, International Agency for Research on Cancer, Lyon, France.

More Articles by Ian Cree

Miguel Reyes-Múgica

Miguel Reyes-Múgica is Marjory K. Harmer Endowed Chair in Pediatric Pathology, Chief of Pathology and Head of Laboratories, Children’s Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, USA

More Articles by Miguel Reyes-Múgica

Explore More in Pathology

Dive deeper into the world of pathology. Explore the latest articles, case studies, expert insights, and groundbreaking research.

False

Advertisement

Recommended

False

Related Content

Case of the Month
Hematology
Case of the Month

January 11, 2022

1 min read

Enriching Our Understanding of Multiple Myeloma
Hematology
Enriching Our Understanding of Multiple Myeloma

February 9, 2022

3 min read

Career Snapshots with Robert Dunn
Hematology
Career Snapshots with Robert Dunn

May 25, 2022

1 min read

Michael Schubert interviews Robert Dunn on working as a biomedical scientist in cytogenetics

A Moment in the Sun
Hematology
A Moment in the Sun

June 23, 2022

4 min read

The decades-long fight for T cells to earn their place in the limelight

False

The Pathologist
Subscribe

About

  • About Us
  • Work at Conexiant Europe
  • Terms and Conditions
  • Privacy Policy
  • Advertise With Us
  • Contact Us

Copyright © 2025 Texere Publishing Limited (trading as Conexiant), with registered number 08113419 whose registered office is at Booths No. 1, Booths Park, Chelford Road, Knutsford, England, WA16 8GS.