Interpreting Hematology Values

The lab’s role in interpreting tests has expanded to collaborate more closely with doctors, nurses, patients and family members

Laboratory professionals find the unexpected. They “collect samples and perform tests to analyze body fluids, tissue and other substances,” as described by the US Bureau of Labor Statistics.1 But lab work isn’t just drawing blood and pushing buttons. Results must be interpreted in quality and clinical contexts before reporting, leading to a richer understanding of patient care that makes bench work rewarding and interesting.

Why interpret?

Wait a moment. Isn’t interpretation the job of the physician? Lab techs aren’t trained to interpret diagnostic tests. They don’t make treatment decisions, but physicians and other clinicians do using laboratory test results that they assume are reliable. To ensure that results are reliable (e.g., accurate and precise), techs must interpret values in an appropriate context-in many cases, with awareness of the clinical setting and possible treatment. In fact, this happens routinely in laboratories thousands of times each day.

For example, as interpreted from serial specimens, cardiac troponin levels rise and fall during an acute myocardial infarction. An instrument may flag or repeat an abnormal result, but it is the job of the bench tech to be aware of the expected pattern (a rise and fall in values) and look for deviations that indicate a problem with the sample or analysis. A greater-than-expected drop or rise in values should prompt the tech to check the sample label and integrity, check quality control and reagent levels, repeat the test, etc.

Understanding what makes laboratory tests meaningful to clinicians leads to greater job satisfaction. While common management wisdom teaches that employees are motivated by pay rates, raises and bonuses, the number one motivator is the feeling of making progress each day toward a goal.2We all want our work to be meaningful in a personal sense, which, for many, means developing a mastery over time that makes a difference in the lives of others.

Web service Blinkist cofounder Sebastian Klein refers to the “passion trap” of expecting to find a career one loves first and be motivated second, when, instead, a passion for work is built slowly through experience.

“The craftsman’s mindset acknowledges that, no matter what field you’re in, success is always about quality,” he wrote in Fast Company. “Once you’re focused on the quality of the work you’re doing now rather than whether or not it’s right for you, you won’t hesitate to do what is necessary to improve it.”3

Interpreting Hematology Values

A CBC (complete blood count) is a common laboratory panel to screen for and monitor disease such as anemia and leukemia. The characteristics of white and red blood cells make this test a unique indicator of both acute (e.g., sepsis) and chronic (e.g., iron deficient anemia) conditions. For both the experienced and the new bench tech, interpreting a CBC starts with the basics:

Normal ranges – Your information system will automatically flag a result as low, high or critical depending on age and sex of the patient. It’s a good idea to have an expectation of what is normal for your patient population, too, since reference ranges are often supplied by an instrument manufacturer or are challenging to verify for certain age groups (e.g., pediatrics) in a rural hospital setting.

Delta checking – Comparing a current to previous value can be done manually or as configured in your information system. This can be useful to flag a sudden change in hemoglobin, for example, that may be unexpected (e.g., acute bleed) or expected (e.g., a rise following a transfusion). The lifecycle of red cells make the MCV and indices (MCH, MCHC) useful in troubleshooting specimen problems.

A 2006 study concludes that a shift has happened in the role of the patient from passive recipient to active consumer of information. Patients search online before seeking help to see if it’s necessary and after for reassurance or to critique.4 The elderly and those without online access may not search themselves, but as Susannah Fox of the Pew Internet and American Life Project told NPR, “It’s the friends and family who surround them who are able to do research on their behalf.”5 As online health information becomes commonplace, it is changing everyone’s role in medicine, including laboratory professionals.

Answering a patient’s question about a CBC with, “You’ll have to ask your doctor,” is now poor customer service, because expectations have changed. Each tech should explain the basics to patients and family members-what the tests measure, what ranges and flags mean and where to find answers online.

Interpreting Disease

A tech on the bench isn’t just running normal specimens all day, however. Results should be interpreted as possible indicators of disease states and compared to patient diagnosis or history. This helps techs make a leap from, “Did the instrument run the test correctly?” to, “Are these results believable for this patient?” In that sense, it improves quality.

For example, a macrocytic anemia (increased MCV of 100-110 fL or higher) with a microscopic review of a peripheral blood smear may indicate a number of conditions as indicated in the Table. Certain drugs, such as hydroxyurea (used to treat myeloproliferative disorder) and zidovudine (used to treat HIV infection), alcohol consumption and nutritional deficiencies in vitamin B12 or folate, are common causes of macrocytic anemia. A bench tech should compare the cluster of clues (RDW, presence of oval macrocytes, etc.) with patient signs and symptoms.

Finding results that are unexpected without explanation should prompt an investigation. Is there a specimen or instrument error? Are the results reproducible? A telephone call to the nurse or provider caring for the patient can be instructive. While this kind of investigation can be time consuming in the midst of a daily workload, it helps improve overall quality.

As patients have become educated consumers with online healthcare advice and information, our role in interpreting laboratory tests has expanded to collaborate more closely with doctors, nurses, patients and family members. Laboratory professionals have new opportunities to apply knowledge at the bench, leading to better patient care.

Table: Macrocytic Anemia6

Differential Diagnosis CBC Peripheral blood smear
Drug-induced (hydroxyurea, zidovudine) Increased RDW
Marked or mild macrocytosis
Oval macrocytes
Nutritional Increased RDW
Marked or mild macrocytosis
Oval macrocytes
Hypersegmented neutrophils
Myelodysplastic syndrome or other bone marrow disorder Increased RDW Oval macrocytes

Dimorphic RBCs

Pseudo Pelger-Huëtt anomaly cells (hyposegmented neutrophils)

Liver disease, chronic alcohol use Normal RDW


Round macrocytes

Target cells

Hypothyroidism Normal RDW Round macrocytes
Hemolysis Normal or elevated RDW  Polychromasia (reticulocytosis)



  1. Medical and Clinical Laboratory Technologists and Technicians: Occupational Outlook Handbook: U.S. Bureau of Labor Statistics.
  2. Chen W. The Science Behind What Motivates Us to Get Up for Work Every Day.The Buffer Blog.
  3. Klein S. The Secrets To Career Contentment: Don’t Follow Your Passion. Fast Company.
  4. McMullen M. Patients Using the Internet to Obtain Health Information: How This Affects the Patient-health Professional Relationship. PubMed, NCBI. Ncbinlmnihgov.
  5. Shapiro J. Patients Turn to the Internet for Health Information.
  6. Tefferi A, Hanson C, Inwards D. How to Interpret and Pursue an Abnormal Complete Blood Cell Count in Adults. Mayo Clinic Proceedings. 2005;80(7):923-936. doi:10.4065/80.7.923.

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