What is the best approach to manage a patient with leukocytosis (elevated white blood cell count) without symptoms in a Skilled Nursing Facility (SNF) setting, likely an older adult with multiple comorbidities?

Management of Asymptomatic Leukocytosis in SNF Residents

In an asymptomatic SNF resident with leukocytosis, additional diagnostic testing is generally not indicated due to low yield, but you must first obtain a manual differential to assess for left shift and calculate the absolute band count—if bands are ≥1,500 cells/mm³ or ≥16%, this carries high likelihood ratios (14.5 and 4.7 respectively) for occult bacterial infection requiring careful clinical reassessment and targeted workup. 1, 2

Initial Laboratory Assessment

Obtain a manual differential count immediately to properly assess the leukocytosis, as automated analyzers are insufficient for detecting left shift and band forms. 3, 4

• Calculate the absolute band count: If ≥1,500 cells/mm³, this has the highest likelihood ratio (14.5) for documented bacterial infection, even without fever or symptoms 1, 3, 2
• Assess band percentage: If ≥16%, this represents a left shift with likelihood ratio of 4.7 for bacterial infection 1, 2
• Check neutrophil percentage: If ≥90%, likelihood ratio is 7.5 for bacterial infection 2
• Total WBC ≥14,000 cells/mm³ alone has only a likelihood ratio of 3.7, making the differential more important than the total count 1, 2

Clinical Decision Algorithm

If NO left shift AND patient truly asymptomatic:

Do not pursue additional diagnostic testing. The IDSA explicitly states that in the absence of fever, leukocytosis/left shift, or specific clinical manifestations of focal infection, additional diagnostic tests may not be indicated due to low potential yield. 1, 2

If left shift present (bands ≥1,500 or ≥16%) OR any subtle clinical findings:

Perform targeted assessment for occult bacterial infection, as there is high probability of underlying infection even without fever or obvious symptoms. 1

Critical focused examination to identify occult infection source:

• Respiratory: Check for subtle tachypnea, hypoxemia on pulse oximetry, or new cough—obtain chest radiograph if any respiratory findings present 3, 4
• Urinary: Look for new or worsening incontinence, gross hematuria, or suprapubic tenderness—but do NOT obtain urinalysis/culture in truly asymptomatic residents 1
• Skin/soft tissue: Examine for erythema, warmth, purulent drainage, or pressure ulcers 3
• Abdominal: Assess for peritoneal signs, distension, or diarrhea 3
• Vital signs: Document temperature using oral/rectal method (not tympanic/temporal), blood pressure, heart rate, respiratory rate 4

Special Considerations for SNF Population

Older LTCF residents frequently lack typical infection symptoms, making laboratory findings more critical for detection. 1, 2, 4

• Basal body temperature decreases with age and frailty, so fever definitions are less reliable 2, 4
• Nonspecific symptoms like confusion, anorexia, or functional decline are often attributed to UTI but may not represent true infection 1
• Left shift can occur with normal total WBC count and still indicate serious bacterial infection 3, 2

Critical Pitfalls to Avoid

• Do not ignore elevated band counts when total WBC is only mildly elevated—left shift is more predictive than total WBC count 3, 2
• Do not rely on automated differential alone—manual differential is essential to accurately assess band forms 3, 4
• Do not obtain urinalysis/urine culture in asymptomatic residents, even with leukocytosis, as bacteriuria is nearly universal in SNF residents and does not indicate infection 1
• Do not treat with antibiotics based solely on laboratory findings if patient is truly asymptomatic and hemodynamically stable after thorough assessment 3, 2
• Do not order tests that won't change management—tests should only be performed if they have reasonable yield, low risk, reasonable cost, and will improve patient management 1, 2

When to Escalate Care

Obtain blood cultures and initiate empiric antibiotics if any of the following develop:

• Fever >38°C or hypothermia <36°C 3
• Hypotension <90 mmHg systolic 3
• Tachycardia, tachypnea, or altered mental status 3
• Lactate >3 mmol/L indicating severe sepsis 3

In observational studies, leukocytosis has been associated with increased mortality among LTCF residents with nursing home-acquired pneumonia (WBC ≥15,000 cells/mm³) and bloodstream infection (WBC ≥20,000 cells/mm³). 1