In a patient with a common cold, which white blood cells (WBCs) are typically elevated?

White Blood Cell Elevation in the Common Cold

In a patient with a common cold (viral upper respiratory tract infection), lymphocytes are typically NOT significantly elevated, while neutrophils show selective recruitment and mild-to-moderate elevation. 1, 2

Expected White Blood Cell Pattern in Viral Upper Respiratory Infections

Neutrophil Response

• Selective neutrophil recruitment occurs in viral upper respiratory infections, including the common cold, driven by IL-8 elaboration and representing the primary inflammatory response. 2
• Neutrophil (granulocyte) counts may show mild elevation but remain significantly lower than in bacterial infections—typically well below the bacterial infection thresholds of 10,000-15,000 cells/mm³. 1
• Common cold symptoms correlate directly with rhinovirus-induced IL-8 production and neutrophil activation, not lymphocyte activity. 2

Lymphocyte Response

• Lymphocyte counts have no aetiological association with distinguishing viral from bacterial respiratory infections and are of no diagnostic value in this differentiation. 1
• Absolute lymphocyte counts do not show characteristic elevation in common cold presentations. 1
• In some viral AURTIs (particularly adenovirus), B lymphocytes may increase during acute phase, but this pattern is not typical of rhinovirus common colds. 3

Key Distinguishing Features from Bacterial Infection

Total WBC and Granulocyte Thresholds

• WBC counts ≥15,000-20,000 cells/mm³ have 86-95% specificity for bacterial (not viral) infection. 1
• Granulocyte counts ≥10,000-15,000 cells/mm³ have 84-97% specificity for bacterial infection. 1
• Viral respiratory infections typically maintain WBC and granulocyte counts below these thresholds. 1

Left Shift Absence

• True left shift (band neutrophils ≥16% or absolute band count ≥1,500 cells/mm³) indicates bacterial infection with likelihood ratios of 4.7 and 14.5 respectively, and should not be present in uncomplicated common colds. 4, 5

Clinical Pitfalls to Avoid

• Do not assume lymphocytosis is characteristic of viral respiratory infections—lymphocyte counts lack discriminatory value between viral and bacterial etiologies. 1
• Do not interpret mild neutrophilia as evidence of bacterial superinfection unless accompanied by left shift, high fever, or clinical deterioration—mild neutrophil elevation is part of the normal viral inflammatory response. 2
• Be aware that some viral AURTIs (particularly adenovirus) can mimic bacterial infection with marked WBC elevation and CRP elevation, leading to inappropriate antibiotic use. 3
• Normal or low WBC counts do not rule out bacterial superinfection if clinical symptoms suggest it—sensitivity of WBC for bacterial infection is low. 1