Band counts in infection diagnosis

By Sally Robertson, B.Sc.Nov 8 2012

Even when patients have normal white blood cell (WBC) counts, elevated band counts may diagnose infection and prompt earlier initiation of antibiotics, report researchers.

"Our findings suggest that there are selected patients in whom obtaining manual differentials can contribute to the initial diagnostic evaluation," say Marci Drees (Christiana Care Health System, Wilmington, North Carolina, USA) and colleagues.

"Although many patients with elevated band counts also will have high total white blood cell counts (limiting its additional contribution), we specifically limited our analysis to those patients with normal initial white blood cell counts to try to determine whether bandemia could provide an earlier suggestion of serious infection," they explain in The American Journal of Medicine.

Indeed, the researchers found that higher band counts were associated with a greater likelihood of having any significant positive culture (blood urine, sputum, or wound), but particularly with a greater likelihood of having positive blood cultures and C. difficile infection.

In a retrospective study of 2342 patients with a normal WBC count (3800-10,800 per mm³) on admission to hospital, the researchers found 167 (7.1%) individuals had high band counts (≥20% bands and other immature cells), 205 (8.6%) had intermediate band counts (11-19%), and 1970 (84.1%) had normal band counts.

Analysis showed that significant positive cultures were more frequent in patients with increased bandemia compared with those with normal band counts, at an odds ratio (OR) of 2.0 for those with intermediate bands and 2.8 for those with high bands. For a positive blood culture, the respective ORs were 3.8 and 6.2.

Only 13 cases of C. difficile were confirmed but seven (54%) of them were in the high band group.

"C. difficile is a well-described cause of significant leukocytosis and bandemia, sometimes before the onset of diarrhea, but this study demonstrates that C. difficile also is associated with bandemia in the absence of elevated white blood cell counts."

The team also notes that patients with high bands were more likely to die during their hospitalization or require discharge to long-term care facilities, compared with patients who had normal bands.

"This study suggests that determining whether bandemia is present can be a useful adjunct in the initial diagnostic evaluation in selected patients," says the team. "Early empiric antibiotics should be considered even in the setting of normal total WBC counts and nonspecific clinical signs and symptoms."

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