Background: The prognosis of patients with leukemoid reaction (LR) depends mainly on their underlying illness. Our aim was to investigate the etiologies and prognosis of a mixed group of patients with LR.
Methods: We identified 173 patients who had ≥30.0 × 10(9) leukocytes/µL without hematologic malignancies. Causes of LR and factors contributing to death were analyzed.
Results: Patients with LR constituted 0.59% of all admitted adults. The median age was 75 years, but 20 patients were aged <40 years. There was no difference in LR prevalence by gender (female/male = 88/85). Average white blood cell (WBC) count was 37.7 × 10(9)/µL. Fourteen patients (8.0%) had a WBC count of >50.0 × 10(9)/µL. The median duration of LR was 1 day, but 39 patients had prolonged LR (>1 day). Infection was the most common cause of LR (n = 83, 47.9%; 95% confidence interval, 40.7-55.4), followed by ischemia/stress (27.7%), inflammation (6.9%), and obstetric diagnoses (6.9%). Higher WBC counts were significantly associated with positive blood cultures (P = .017) or a positive Clostridium difficile toxin (P = .001). Antibiotics were prescribed for 140 patients (80.9%). Sixty-six patients (38.1%) died during hospitalization. Those with prolonged LR had an in-hospital mortality rate of 61.5%. Factors found to be highly correlated with death were age (odds ratio [OR] = 1.051, P < .001), any infectious diagnosis (OR = 2.574, P = .014), and sepsis (OR = 3.752, P = .001).
Conclusions: LR carries a grave prognosis, especially among the elderly and those with sepsis. LR was found to have multiple etiologies including infections, stress, inflammation, and obstetric diagnoses.
Keywords: elderly; etiology; extreme leukocytosis; leukemoid reaction; sepsis.