What’s the difference between in vivo and in vitro hemolysis and why should laboratorians take note of this during sample processing? Expert John V. Mitsios, PhD, answers these questions and more in December’s Clinical Laboratory News.

Hemolysis can affect test performance either by increasing analyte concentration due to the release of red blood cell constituents or by increasing or decreasing analyte concentration due to assay interference, Mitsios summarizes.

Correctly identifying in vivo hemolysis and differentiating it from in vitro hemolysis “is of great clinical importance because it is a sign of many different underlying pathological conditions, some of which could be life-threatening if left untreated,” according to Mitsios, assistant director for the special coagulation laboratory at BioReference Laboratories in Elmwood Park, New Jersey. Numerous biochemical, physical, chemical, immunological mechanisms, and/or infections that occur within the body prior to a blood draw can lead to in vivo hemolysis. By comparison, in vitro hemolysis takes place outside of the body and most often results from preanalytical factors such as blood drawing, specimen handling, specimen delivery to the laboratory, or specimen storage.

Mitsios also addresses the pros and cons of using haptoglobin as a marker of in vivo hemolysis.

Beyond hemolysis, a variety of clinical factors can either reduce or elevate haptoglobin concentrations. Some conditions such as hemodilution and blood transfusions can produce falsely reduced haptoglobin concentrations. “Consequently, clinicians as well as laboratorians need to be aware of haptoglobin’s limitations and interactions, and interpret this test in the context of a patient’s clinical scenario,” Mitsios advises.

Learn more about hemolysis testing in the December CLN Ask the Expert column.