Elevated White Blood Cell Count Diagnosis and Management

Introduction to Leukocytosis

The American College of Physicians suggests that a high white blood cell (WBC) count is most commonly caused by bacterial infection, but also results from physiological stress, medications, smoking, obesity, chronic inflammation, and less commonly, hematologic malignancies 1, 2

Bacterial infections are the leading cause of leukocytosis and should be the first consideration, with key diagnostic markers including an absolute band neutrophil count ≥1,500 cells/mm³, neutrophil percentage >90%, left shift (≥16% band neutrophils), and total WBC ≥14,000 cells/mm³ 1, 2
Common bacterial sources include respiratory tract infections, urinary tract infections, skin and soft tissue infections, gastrointestinal infections, and spontaneous bacterial peritonitis in cirrhosis patients with ascites 1

Physical and emotional stress can cause an increase in WBC count due to mobilization from bone marrow storage pools, with exercise and emotional stress being common culprits 2

Corticosteroids are the most common medication cause of leukocytosis, while lithium consistently causes leukocytosis, with a WBC <4,000/mm³ being unusual in lithium-treated patients 1, 2

Smoking and obesity are associated with higher baseline WBC counts, and chronic inflammatory conditions, including inflammatory bowel disease, can also cause leukocytosis 2

A complete blood count with manual differential is essential for assessing bands and immature forms, and calculating absolute neutrophil count and absolute band count 1, 2
Clinical context, including fever, localizing symptoms, or signs of sepsis, should be assessed, and medication lists should be reviewed for corticosteroids, lithium, and beta-agonists 1, 2
Risk stratification based on WBC pattern is crucial, with WBC ≥14,000 with left shift indicating high suspicion for bacterial infection 1, 2

Normal WBC does not exclude bacterial infection, especially in elderly or immunosuppressed patients, and left shift can occur with normal total WBC 1, 2
Serial measurements are more informative than single values for persistent unexplained elevation, and high WBC and granulocyte counts are clear evidence of bacterial etiology, but low or normal values do not rule it out 2