White Blood Counts of Hospitalized Patients Without Infection, Malignancy, or Immune Dysfunction

An elevated white blood cell (WBC) count may indicate malignancy, infection, and immune dysfunction. In diagnosing these conditions, physicians generally evaluate laboratory results compared with reference ranges based on healthy populations. Reference ranges for hospitalized patients are lacking. This study aims to define a normal reference range for WBC count in hospitalized patients without malignancy, infection, or immune dysfunction.

This was a retrospective cross-sectional study of nonsurgical patients hospitalized from 2017 to 2018 in the Cleveland Clinic Health System without malignancy, infection, or immunological dysfunction. WBC count, absolute neutrophil count, and absolute lymphocyte count were collected. We calculated means, standard deviations, and the reference range for each variable.

A total of 46,419 patients had WBC counts. Mean WBC count was 8.0 (standard deviation 3.31, reference range 1.6-14.5). In a multivariable linear regression, mean WBC count decreased with age, Black race relative to White race, and congestive heart failure. Body mass index, diabetes mellitus, chronic kidney disease, chronic obstructive pulmonary disease, and steroid use were associated with higher WBC count. In total, 13.5% of patients in this cohort had WBC counts above the "normal" threshold of 11.

Among hospitalized patients without infection, malignancy, or immune dysfunction, the normal range for WBC count was 1.6 to 14.5 × 10⁹ WBCs/L. Age, race, body mass index, steroid use, and several comorbidities were associated with WBC count variation from the reference levels established based on healthy populations. Physicians should be cautious when interpreting WBC counts between 11 and 14.5 × 10⁹ WBCs/L, which appear to represent normal values in the hospital.