Understanding Hematology Histograms: Why Laboratory Interpretation Matters



Hematology analyzers used in veterinary clinics generate a large amount of data during a blood test. Among these outputs are hematology histograms, graphical representations that show the distribution and size of blood cell populations. While these graphs can be useful, they are often misinterpreted in clinical settings when their limitations are not fully understood.

What Hematology Histograms Actually Show

A hematology histogram is a graphical display generated by an automated analyzer that illustrates:

  • Cell size distribution

  • Relative cell population counts

  • Analyzer performance indicators

These graphs are produced as the machine processes the blood sample, meaning they reflect both biological information and instrument function. In other words, a histogram may change because of:

  • A real shift in blood cell populations

  • Sample quality issues

  • Machine calibration or analyzer limitations

Understanding the difference between these possibilities requires specific training.

Why Medical Laboratory Technologists Interpret Them More Accurately

Professionals trained in laboratory medicine, such as medical laboratory technologists, are specifically educated to interpret analyzer outputs, including histograms and scatter plots. Their training focuses on distinguishing:

  • True biological abnormalities in blood cells

  • Instrument artifacts caused by machine limitations or sample issues

Because histograms contain information about both the blood sample and the analyzer’s performance, misinterpretation can occur if the operator assumes every variation reflects a disease process.

Laboratory technologists are trained to identify when:

  • The analyzer is producing an artifact

  • The sample may be compromised

  • The graph reflects a true shift in cell size or population

Why Numeric Reference Values Are More Reliable in Many Clinical Settings



Disclaimer- SAMPLE REPORT: Client, clinic, and patient details are fictional. Blood work results are genuine, valid data."

In many veterinary clinics, a more practical and reliable way to interpret bloodwork is through numeric result indicators with established reference ranges.

These include:

  • White blood cell counts

  • Red blood cell counts

  • Hemoglobin and hematocrit values

  • Platelet counts

  • Biochemical values

These numerical values with reference ranges provide clearer clinical interpretation and are easier to integrate into treatment decisions.

Companies that specialize in veterinary diagnostic equipment, such as IDEXX Laboratories and Abaxis VetScan, Antech (known for chemistry analyzers), design systems that emphasize reference-based numeric interpretation for this reason.

Why This Matters for Patient Care

Blood diagnostics should provide clear, actionable information. Overreliance on analyzer graphics like histograms without the proper laboratory training can lead to:

  • Misinterpretation of machine artifacts

  • Incorrect assumptions about disease

  • Delays in appropriate diagnostics or treatment

Numeric values interpreted alongside clinical signs, patient history, and additional diagnostics remain the most reliable approach in everyday veterinary practice.

Summery

Hematology histograms can be useful tools, but they are not standalone diagnostic indicators. Proper interpretation requires an understanding of both analyzer mechanics and blood cell biology—skills typically emphasized in laboratory medicine training.

For most veterinary clinics, numerical lab values with reference ranges, supported by modern diagnostic systems and proper clinical evaluation, provide the most accurate and practical foundation for patient care.

Resources

Cowell, R. L., Tyler, R. D., Meinkoth, J. H., & DeNicola, D. B. (2020). Diagnostic cytology and hematology of the dog and cat (5th ed.). Elsevier.

Harvey, J. W. (2012). Veterinary hematology: A diagnostic guide and color atlas. Elsevier Saunders.

Latimer, K. S., Mahaffey, E. A., & Prasse, K. W. (2011). Duncan and Prasse’s veterinary laboratory medicine: Clinical pathology (5th ed.). Wiley-Blackwell.

Stockham, S. L., & Scott, M. A. (2013). Fundamentals of veterinary clinical pathology (2nd ed.). Wiley-Blackwell.

Thrall, M. A., Weiser, G., Allison, R. W., & Campbell, T. W. (2012). Veterinary hematology and clinical chemistry (2nd ed.). Wiley-Blackwell.

Antech Diagnostics. (2023). Veterinary diagnostic laboratory services and clinical pathology resources. https://www.antechdiagnostics.com

IDEXX Laboratories. (2024). Veterinary diagnostic testing and reference laboratory services. https://www.idexx.com

American Society for Clinical Pathology. (2022). Understanding hematology analyzer technology and laboratory interpretation. https://www.ascp.org


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