Differentiating Upper Respiratory Infection, Viral Illness, Bronchitis, and Pneumonia

Key Clinical Algorithm for Differentiation

The European Respiratory Society recommends suspecting pneumonia when acute cough is present plus any one of the following: new focal chest signs on examination, dyspnoea or tachypnoea, pulse rate >100 beats/min, fever lasting >4 days, or temperature >38°C 1, 2, 3
The European Respiratory Society suggests that if all four of the following are absent, pneumonia is sufficiently unlikely that chest radiography can be omitted: heart rate >100 beats/min, respiratory rate >24 breaths/min, oral temperature >38°C, and focal chest examination findings 1, 2, 5
CRP testing provides valuable diagnostic information when pneumonia is suspected, with CRP <20 mg/L with symptoms >24 hours making pneumonia highly unlikely, and CRP >100 mg/L making pneumonia likely 3, 4

The European Respiratory Society recommends considering chest X-ray even with fewer clinical findings in patients ≥65 years, those with COPD, diabetes, or heart failure, and those with previous hospitalization in the past year, oral glucocorticoid use, or recent antibiotic use 3, 4, 6, 9

The European Respiratory Society suggests assessing for underlying COPD or asthma when patients present with persistent cough and at least two of the following: wheezing, prolonged expiration, smoking history, symptoms of allergy, or previous consultations for wheezing or cough 2, 3, 9
Approximately 40% of patients with acute bronchitis have transient bronchial hyperresponsiveness mimicking asthma 4

The European Respiratory Society advises against assuming all pulmonary infiltrates with fever are infectious, as fever, leukocytosis, and infiltrates occur in both infectious pneumonia and non-infectious pneumonitis 8
The European Respiratory Society recommends against delaying antibiotics if pneumonia cannot be excluded, as delayed appropriate antimicrobial therapy increases mortality 8

The Clinical Microbiology and Infection society recommends that in primary care, microbiological tests such as cultures and gram stains are NOT recommended for routine LRTI evaluation 3
The Clinical Microbiology and Infection society advises that biomarkers to assess bacterial pathogens are not recommended in primary care settings 3
The European Respiratory Society states that the gold standard for pneumonia diagnosis remains chest radiography, not clinical examination alone 1, 2