Why reticulocytes can be a great early indicator that something is wrong

Historically, reticulocyte counts were only considered on patients where anemia was suspected, as they assist in classifying the anemia as regenerative or nonregenerative. However, recent data suggests that the benefits of running reticulocytes are much broader because they can provide advanced, critically important information on the health of all patients, regardless of the presence of anemia.

By including reticulocyte counts (RETICs) and reticulocyte hemoglobin (RETIC-HGB) in every complete blood count (CBC), it’s possible to detect—and subsequently diagnose and treat—a variety of issues earlier than with traditional CBCs. Here’s why:

Reticulocytes act as an early warning system

Red blood cells (RBCs) circulate in the body between 80 –120 days, depending upon the species and clinical health of the animal. Since RBC indices are reflective of the bone marrow environment at the time of RBC production, information gained from a traditional CBC may suggest a clinical picture that is significantly different than the current condition of the animal because the RBCs may have been produced several months prior.

Newly released reticulocytes, on the other hand, circulate for only 2–4 days. This makes them excellent early indicators for conditions such as blood loss or inflammation before development of anemia.

Reticulocytosis (increased RETICs) without anemia can be a key indicator that the bone marrow is responding to a need for increased red blood cell production. Causes include compensated blood loss or hemolysis and hypoxia. Determining the underlying cause will require further investigation, but early detection provides the best chance for early treatment and better outcomes for patients.

Low RETIC-HGB can be an initial sign of serious disease

While RETICs measure the quantity of new RBCs, RETIC-HGB reflects the quality—generally related to the amount of iron available during the formation of these cells. The most common causes of low RETIC-HGB are blood loss and inflammatory disease, which both lead to decreased iron availability for RBC production. A low RETIC-HGB result may indicate serious underlying disease before an increase in RETICs or anemia, warranting further exploration.

What could CBCs lacking reticulocyte parameters miss?

A recent study of 1 million canine CBCs1 found that almost 1 in 5 nonanemic patients had changes in their reticulocyte parameters:

  •  Six percent had no anemia, but a high reticulocyte count.
  • Twelve percent had no anemia or reticulocytosis, but had low RETIC-HGB concentration.

This research indicates that reticulocyte parameters should be evaluated with every CBC: Don’t wait for the anemia to develop.

Not all CBCs include reticulocyte parameters. When choosing a CBC, look for those that automatically include reticulocytes.

To learn more about why reticulocytes count, take this archived webinar today.


1 Data collected from 1 million canine CBCs performed worldwide with the ProCyte Dx® Hematology Analyzer in 2017. Evaluation for presence of anemia, RETICS, and RETIC-HGB indicated that 18% of
nonanemic patients had reticulocyte parameters that suggested further clinical evaluation is warranted.  Data on file at IDEXX Laboratories, Inc. Westbrook, Maine, USA.



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