A degenerative left shift (DLS) describes a neutrophil pattern in which there are a larger number of immature granulocytic precursors as compared to mature neutrophils. In cats, bone marrow has a large storage reserve of neutrophils. When the demand for neutrophils exceeds this reserve, the bone marrow releases granulocytic precursors into the blood circulation, resulting in DLS.
This retrospective case-control study of 108 cats with DLS and 322 control cats presenting to a veterinary hospital sought to determine if cats presenting with DLS had an increased risk of euthanasia or death. Disease categories included septic peritonitis, pyothorax, FeLV, wounds, and other. The authors found that cats diagnosed with DLS were 1.57 times more likely to die or be euthanized in hospital when compared to control cats with the same disease. In addition, cats with increased DLS severity were at increased risk for death or euthanasia.