Diagnostic Criteria for Bacterial Sinusitis
The diagnosis of acute bacterial sinusitis should be made when a patient presents with one of three specific clinical presentations: (1) persistent illness with symptoms lasting >10 days without improvement, (2) worsening course after initial improvement, or (3) severe onset with concurrent fever ≥39°C/102.2°F and purulent nasal discharge for at least 3 consecutive days. 1, 2
Clinical Presentations
1. Persistent Illness
- Nasal discharge (of any quality: thin, thick, clear, or purulent)
- Daytime cough (which may be worse at night)
- Symptoms lasting >10 days without improvement 1, 2
2. Worsening Course (Double-sickening)
- Initial improvement of respiratory symptoms followed by
- Worsening or new onset of nasal discharge, daytime cough, or fever 1, 2
3. Severe Onset
- Concurrent high fever (≥39°C/102.2°F)
- Purulent nasal discharge
- Symptoms present for at least 3 consecutive days 1, 2
Key Symptoms and Signs
Prominent Symptoms
- Nasal congestion
- Purulent rhinorrhea
- Facial or dental pain (especially when unilateral)
- Postnasal drainage
- Headache
- Cough 1, 3
Clinical Signs
- Sinus tenderness on palpation
- Mucosal erythema
- Purulent nasal secretions
- Increased pharyngeal secretions
- Periorbital edema 1
Diagnostic Approach
Clinical Diagnosis
The diagnosis of bacterial sinusitis is primarily clinical, based on history and physical examination. A history of persistent purulent rhinorrhea, postnasal drainage, and facial pain correlates with increased likelihood of bacterial disease 1.
Imaging Studies
- Not recommended for routine diagnosis of uncomplicated acute bacterial sinusitis 1, 2
- High rate of false positives: 87% of young adults recovering from colds and 42% of healthy children show sinus abnormalities on imaging 2
- CT scan should only be obtained when orbital or central nervous system complications are suspected 1, 2
Laboratory Tests
- Sinus aspiration with culture is the gold standard but rarely performed in primary care settings 1
- Nasal/nasopharyngeal cultures are unreliable and not recommended 1
- Endoscopically directed middle meatal cultures may correlate with maxillary sinus aspirates but evidence is limited 1
Differential Diagnosis
- Viral upper respiratory infection
- Allergic rhinitis
- Eosinophilic non-allergic rhinitis
- Vasomotor rhinitis
- Vascular headaches/migraines 1
Common Pathogens
- Adults: Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis
- Children: Same as adults, with higher prevalence of M. catarrhalis
- Chronic sinusitis: Above pathogens plus Staphylococcus aureus, Pseudomonas aeruginosa, and anaerobes 4, 5
Common Pitfalls to Avoid
Overdiagnosis and unnecessary antibiotic use: Most cases of acute rhinosinusitis are viral in origin and resolve without antibiotics 6
Relying on imaging for diagnosis: Sinus abnormalities on imaging are common in asymptomatic individuals and those with viral URIs 2
Misinterpreting purulent discharge: The transition from clear to purulent to clear discharge can occur in uncomplicated viral URIs without antibiotics 1
Failure to recognize complications: Be vigilant for orbital or intracranial complications requiring immediate attention and imaging 1
Inadequate follow-up: Patients should be reassessed if symptoms worsen or fail to improve within 72 hours of initial management 2
By applying these diagnostic criteria systematically, clinicians can more accurately identify patients with true bacterial sinusitis who may benefit from antibiotic therapy, while avoiding unnecessary treatment in those with viral infections.