What is the appropriate management for a patient with leukocytosis and neutrophilia, suggesting a potential bacterial infection?

Management of Leukocytosis and Neutrophilia Without Fever

This patient requires immediate systematic evaluation for bacterial infection despite the absence of fever, as a WBC count of 14,300 cells/mm³ with absolute neutrophil count of 11,097 cells/mm³ has a likelihood ratio of 3.7 for underlying bacterial infection. 1

Immediate Diagnostic Steps

Obtain a manual differential count immediately to assess band forms and other immature neutrophils, as automated analyzers are insufficient for this critical determination. 1 An absolute band count ≥1,500 cells/mm³ has the highest likelihood ratio (14.5) for detecting documented bacterial infection, and a left shift (percentage of band neutrophils ≥16%) has a likelihood ratio of 4.7 for bacterial infection, even with a normal total WBC count. 1

The absence of fever does not exclude bacterial infection, particularly in older adults where typical symptoms are frequently absent. 1 This is a critical pitfall—do not dismiss the significance of leukocytosis simply because fever is absent. 1

Systematic Source Identification

Respiratory System

• Obtain a chest radiograph to evaluate for pneumonia, as leukocytosis has been associated with increased mortality in nursing home-acquired pneumonia. 1
• Consider pulse oximetry if any respiratory symptoms are present. 1

Urinary Tract

• Do NOT perform urinalysis or urine culture if the patient is completely asymptomatic, as asymptomatic bacteriuria should not be treated. 1
• If urinary symptoms are present, perform urinalysis for leukocyte esterase and microscopic examination for WBCs. 1
• Only obtain urine culture if pyuria is present (≥10 WBCs/high-power field or positive leukocyte esterase). 1

Other Systems

• Perform a detailed examination for potential foci of infection including skin, oropharynx, perineal region, and gastrointestinal tract. 2
• Check clinical records for past positive microbiology, particularly previous antibiotic-resistant organisms or bacteremia. 2

Management Algorithm

If Clinical Signs of Infection Present or Elevated Band Count

Initiate empiric antimicrobial therapy if the patient has other signs of infection or if band count is elevated, given the high likelihood ratio for bacterial infection. 1 The choice of antibiotics should be based on the identified source and local resistance patterns. 1

• Limit antibiotic duration to 4-7 days if source control is adequate. 1
• Serial WBC counts are essential to track response to therapy. 1

If Completely Asymptomatic with No Clinical Signs

Do NOT initiate antibiotics based solely on the elevated WBC count if the patient is completely asymptomatic with no clinical signs of infection. 1

• Monitor closely with repeat CBC in 12-24 hours and reassess for development of symptoms. 1
• A repeat complete blood count with peripheral smear may provide helpful information, such as types and maturity of white blood cells, uniformity of white blood cells, and toxic granulations. 3

Alternative Etiologies to Consider

If infection is ruled out, consider nonmalignant causes of leukocytosis including:

• Recent surgery, exercise, trauma, or emotional stress (can double WBC count within hours). 3
• Certain medications, asplenia, smoking, obesity, or chronic inflammatory conditions. 3

If malignancy cannot be excluded or another more likely cause is not suspected, referral to a hematologist/oncologist is indicated. 3 Symptoms suggestive of hematologic malignancy include fever, weight loss, bruising, or fatigue. 3

Critical Pitfalls to Avoid

• Do not rely on automated differential counts alone—manual differential is necessary to accurately assess band forms. 1
• Do not treat asymptomatic bacteriuria discovered during workup, as this does not improve outcomes and promotes resistance. 1
• Do not overlook inadequate source control as the cause of persistent leukocytosis—imaging and surgical consultation are essential if infection signs persist beyond 7 days. 4