Measuring immature white blood cell forms (“bands”) has been considered clinically unnecessary. We performed this study to determine whether elevated band counts, with normal total white blood cells on admission, were associated with infection or in-hospital death.

We performed a retrospective cohort study including all patients admitted to the Christiana Care Health System 2-hospital, 1100-bed community-based academic health system in 2009 with normal white blood cells (3800-10,800 per mm³) on admission who had manual differentials performed. We defined our band groups as normal (≤10% bands and other immature cells), moderate (11%-19%), or high (≥20%). Via chart review, we ascertained vital signs and culture results for all patients with elevated bands and 407 randomly sampled patients with normal bands. Cultures likely to be contaminants were excluded. We used multivariable logistic regression to determine whether bandemia was predictive of significant positive cultures or death.

Of 2342 patients, 167 (7.1%) had high bands and 205 (8.6%) had moderate bands. The mean white blood cell count was 7.5 cells/mm³, with no difference among groups. Bandemia was associated with increased odds of having any significant positive culture (adjusted odds ratio [OR], 2.0, 95% confidence interval [CI], 1.3-3.1 for moderate bands; adjusted OR, 2.8, 95% CI, 1.7-4.3 for high bands) and having positive blood cultures (adjusted OR, 3.8, 95% CI, 2.0-7.2 for moderate bands; adjusted OR, 6.2, 95% CI, 3.2-11.8 for high bands). Patients with moderate or high bands also had increased odds of in-hospital death (adjusted OR, 3.2, 95% CI, 1.7-6.1; adjusted OR, 4.7, 95% CI, 2.4-9.0, respectively).

Even with normal total white blood cells, patients with moderate and high bandemia on admission had significantly increased odds of having positive cultures, including blood cultures, and of in-hospital mortality.