- Markedly elevated leukocyte (particularly neutrophil) count without hematologic malignancy
- Cutoff is variable, 25-50k
Retrospective review of 135 patients with WBC >25k 
- 48% infection
- 15% malignancy
- 9% hemorrhage
- 12% glucocorticoid or granulocyte colony stimulating therapy
Retrospective review of 173 patients with WBC >30k 
- 48% infection (7% C. difficile)
- 28% tissue ischemia
- 7% obstetric process (vaginal or cesarean delivery)
- 5% malignancy
Observational study of 54 patients with WBC >25k 
- Consecutive patients presenting to the emergency department
- Compared to age-matched controls with moderate leukocytosis (12-24k)
- Patients with leukemoid reaction were more likely to have an infection, be hospitalized and die.
- Signs/symptoms of underlying pathology or asymptomatic
- Tissue ischemia
- Malignancy, paraneoplastic
- Treat underlying condition
- Sakka V, Tsiodras S, Giamarellos-Bourboulis EJ, Giamarellou H. An update on the etiology and diagnostic evaluation of a leukemoid reaction. Eur J Intern Med. 2006;17(6):394-398. doi:10.1016/j.ejim.2006.04.004.
- Reding MT, Hibbs JR, Morrison VA, Swaim WR, Filice GA. Diagnosis and outcome of 100 consecutive patients with extreme granulocytic leukocytosis. Am J Med. 1998;104(1):12-16.
- Potasman I, Grupper M. Leukemoid reaction: spectrum and prognosis of 173 adult patients. Clin Infect Dis. 2013;57(11):e177-e181. doi:10.1093/cid/cit562.
- Lawrence YR, Raveh D, Rudensky B, Munter G. Extreme leukocytosis in the emergency department. QJM. 2007;100(4):217-223. doi:10.1093/qjmed/hcm006.