Normal Differential Count Values by Age

Age-Specific Normal Values

For healthy adults, the normal differential count shows approximately 85-95% alveolar macrophages, 4-15% lymphocytes, 0.5-4% neutrophils, 0.1-0.5% eosinophils, and <0.5% basophils in bronchoalveolar lavage specimens, with age-related increases in lymphocytes and neutrophils observed in individuals over 65 years 1
The American Thoracic Society recommends that at least 400 cells should be counted on cytocentrifuge preparations for reliable differential counts 1
Age-correction is necessary when interpreting differential counts in patients over 50 years, as physiologic increases in neutrophils and lymphocytes can be misinterpreted as pathologic if younger adult reference ranges are applied 2

Current smokers demonstrate a distinctive pattern with markedly elevated total cell counts but paradoxically higher macrophage percentages due to suppressed lymphocyte populations 1

Abnormal differential counts indicating pathology are defined as: lymphocytosis >15% lymphocytes 1, neutrophilia >3% neutrophils 2, eosinophilia >1% eosinophils 2, and mastocytosis >0.5% mast cells 1

Manual differential counting is essential for accurate assessment rather than relying solely on automated analyzers, particularly when evaluating band forms and immature neutrophils in suspected bacterial infections 7
An elevated total band count ≥1,500 cells/mm³ has the highest likelihood ratio (14.5) for bacterial infection, while band percentage ≥16% has a likelihood ratio of 4.7 3