Hemolyzed Specimens: A Reason for Rejection or a Clinical Challenge?

Clinical laboratories must improve the preanalytical phase, a phase highly susceptible to mistakes (1). In some reports, hemolyzed specimens, the most common reason for rejection, account for ∼60% of rejected specimens, fivefold more than the second most common cause (2). Cellular contents can falsely increase values for some plasma constituents, such as potassium, lactate dehydrogenase, and aspartate aminotransferase (3). Moreover, hemolysis produces spectrophotometric interference with other laboratory methods. In vitro hemolysis depends mainly on the way in which the blood samples are drawn and treated, and it may in particular depend on the blood being forced through too fine a needle (4) or through the large-bore needle of a syringe into a tube; it may also be caused by shaking the tube too vigorously and/or centrifuging blood specimens before clotting is complete. In vivo hemolysis, on the other hand, may have at least 50 causes. We evaluated the causes of hemolysis in samples received by our STAT section in the Department of Laboratory Medicine of the University Hospital of Padova, which performs all clinical chemistry tests on specimens collected using lithium heparin as anticoagulant (Becton Dickinson).