What does a white blood cell (WBC) count of 12.5 and a neutrophil count of 8.3 indicate in a patient with a chronic cough lasting 1-2 months?

WBC 12.5 and Neutrophils 8.3 in Chronic Cough: Interpretation and Clinical Approach

A WBC of 12.5 with neutrophils of 8.3 in a patient with 1-2 months of cough suggests a mild leukocytosis with neutrophil predominance, which is nonspecific but may indicate ongoing bacterial infection, persistent inflammation, or simply be within normal variation—however, this finding does NOT establish the diagnosis and you must systematically evaluate for the common causes of chronic cough (upper airway cough syndrome, asthma, GERD, and eosinophilic bronchitis) rather than focusing on the blood count alone. 1, 2

Understanding the Laboratory Values

• The WBC count of 12.5 (×10⁹/L) represents mild leukocytosis, as normal range is typically 4.0-11.0 3
• The neutrophil count of 8.3 (×10⁹/L) shows neutrophil predominance, which can occur with bacterial infections, but is nonspecific in the context of chronic cough 1
• These values do NOT distinguish between the common causes of chronic cough and should not drive your diagnostic approach 1, 2

Critical First Steps: Mandatory Baseline Evaluation

Before attributing significance to the blood count, you must complete the following:

• Obtain a chest X-ray immediately—approximately 31% will show abnormalities that yield a diagnosis, including pneumonia, tuberculosis, malignancy, or bronchiectasis 2, 1
• Perform spirometry with bronchodilator response to identify airflow obstruction and assess for asthma, even though normal spirometry does not exclude asthma or eosinophilic bronchitis 2, 1
• Assess for ACE inhibitor use and discontinue if present, as this can cause chronic cough that resolves within days to weeks (median 26 days) 1
• Confirm smoking status and counsel cessation if applicable, as chronic bronchitis from smoking typically resolves within 4 weeks of quitting 1

Differential Diagnosis Framework for Chronic Cough

The four conditions that account for the vast majority of chronic cough cases are: 1, 2, 4

1. Upper Airway Cough Syndrome (UACS)

• Most common cause of chronic cough 1, 4
• Can present with cough alone without other rhinosinus symptoms ("silent PNDS") 1
• Empiric trial: First-generation antihistamine plus decongestant 2, 5

2. Asthma (Including Cough-Variant Asthma)

• Can present with isolated cough and normal spirometry 1, 2
• Empiric trial: Inhaled corticosteroids and bronchodilators, or prednisolone 30-40 mg daily for 2 weeks 2, 1
• Response to therapy confirms the diagnosis 1

3. Gastroesophageal Reflux Disease (GERD)

• Can be "silent" with no heartburn or regurgitation symptoms 1
• Empiric trial: Proton pump inhibitor therapy for minimum 2 months, combined with dietary/lifestyle modifications 2, 1
• Medical therapy improves cough in 70-100% when not limited to acid suppression alone 1

4. Nonasthmatic Eosinophilic Bronchitis (NAEB)

• Characterized by: Cough, eosinophilic infiltration, normal spirometry, lack of bronchial hyperresponsiveness 1
• Diagnosis requires: Induced sputum analysis showing eosinophilia (>3% eosinophils) 1
• Treatment: Inhaled corticosteroids with excellent response 1
• Prevalence: 13-33% in some series, though oddly underreported in U.S. studies 1

When to Consider Infectious Causes

Given the mild leukocytosis with neutrophilia, consider:

Pertussis (Bordetella pertussis)

• Key features to assess: Paroxysmal cough, post-tussive vomiting, inspiratory whooping, absence of fever 3, 2
• Prevalence: Approximately 10% of chronic cough cases in some series had positive Bordetella testing 2, 1
• Testing: Nasopharyngeal culture or PCR if clinical features present 2

Tuberculosis

• Consider in endemic areas or high-risk populations regardless of cough duration 3, 2
• Red flag symptoms: Weight loss, night sweats, hemoptysis 3, 1
• Testing: Sputum smears and cultures for acid-fast bacilli along with chest radiography 2

Protracted Bacterial Bronchitis

• More common in children but can occur in adults 4
• Neutrophilic inflammation may be detected on induced sputum 1

Red Flag Symptoms Requiring Urgent Evaluation

• Hemoptysis (coughing up blood) 3, 2
• Finger clubbing, especially with pleural effusion or lobar collapse suggesting lung cancer 1, 2
• Unexplained weight loss 3, 1
• Recurrent pneumonia 3
• Hoarseness persisting with cough 3
• Dysphagia 3

Recommended Diagnostic Algorithm

Step 1: Complete mandatory baseline investigations (chest X-ray, spirometry) 2, 1

Step 2: If chest X-ray is abnormal, investigate the specific finding rather than proceeding with chronic cough algorithm 1, 2

Step 3: If chest X-ray is normal, initiate empiric treatment for the most likely causes simultaneously: 1, 2

• UACS: First-generation antihistamine + decongestant
• Asthma: Inhaled corticosteroids + bronchodilators (or trial of prednisolone 30-40 mg daily for 2 weeks)
• GERD: PPI therapy for minimum 2 months with lifestyle modifications

Step 4: If partial response, maintain all partially effective treatments as multiple causes often coexist 1

Step 5: If no response after 8 weeks of empiric therapy, consider: 2, 1

• Induced sputum analysis for eosinophilia (NAEB) or neutrophilia (bacterial bronchitis)
• High-resolution CT chest if interstitial lung disease suspected
• Referral to pulmonologist

Critical Pitfalls to Avoid

• Do not attribute the cough solely to the mild leukocytosis—this is nonspecific and does not establish causation 1, 2
• Do not prescribe antibiotics empirically without evidence of bacterial infection on imaging or sputum analysis 1, 2
• Do not rely on cough characteristics (timing, quality, productive vs. nonproductive) to rule in or rule out specific diagnoses, as these lack sensitivity and specificity 1
• Do not stop partially effective treatments when adding new therapies, as chronic cough often has multiple simultaneous causes 1
• Do not use single peak flow measurements for diagnosis—they are less accurate than FEV1 for identifying airflow obstruction 2

Special Consideration: Sputum Analysis

• If diagnosis remains unclear after empiric trials, induced sputum analysis can differentiate: 1
  • Eosinophilia (>3%): Suggests NAEB or asthma—treat with inhaled corticosteroids
  • Neutrophilia: Suggests viral or bacterial infective bronchitis
  • Normal cell counts: Consider GERD, UACS, or cough hypersensitivity syndrome

The mild elevation in WBC and neutrophils should prompt you to ensure infectious causes are not missed, but the systematic evaluation for the common causes of chronic cough (UACS, asthma, GERD, NAEB) remains your primary diagnostic strategy. 1, 2