Diagnostic Criteria for Bacterial Sinusitis
Acute bacterial sinusitis should be diagnosed when upper respiratory symptoms persist beyond 10-14 days without improvement, or when symptoms worsen within 5-10 days after initial improvement ("double worsening"), particularly when accompanied by persistent purulent rhinorrhea and facial pain. 1, 2
Three Clinical Presentations for Diagnosis
The diagnosis is based on one of three distinct patterns 3:
- Persistent symptoms: Nasal discharge or cough lasting >10 days but <30 days without improvement 1, 2, 3
- Severe onset: Concurrent high fever (≥39°C) and purulent nasal discharge for at least 3 consecutive days 1, 4, 3
- Worsening course ("double sickening"): Initial improvement followed by new onset or worsening of fever, headache, or nasal discharge within 5-10 days 5, 3
Key Symptoms with Highest Diagnostic Value
The combination of symptoms matters more than individual findings 1:
- Persistent purulent rhinorrhea (thick, colored nasal discharge) combined with facial pain has the strongest correlation with bacterial disease 1, 2, 4
- Maxillary tooth or facial pain, especially unilateral 1, 6
- Nasal congestion 1, 2
- Postnasal drainage 1, 2
- Headache 1, 2
- Cough, particularly worse at night 1, 2
Physical Examination Findings
Clinical signs alone are not sufficient for diagnosis but support the clinical picture 1:
- Unilateral maxillary sinus tenderness on palpation 1, 6
- Purulent nasal secretions visible in the middle meatus (yellow-green, green, or gray) 2
- Mucosal erythema and swelling 1
- Periorbital edema 1, 2
Critical Timing Considerations
Do not diagnose bacterial sinusitis before 10 days of symptoms 2, 5:
- Most viral URIs resolve within 5-7 days 2
- Symptoms present for fewer than 7 days are unlikely to represent bacterial infection 1
- At day 7 without worsening, bacterial infection is unlikely 5
- The 10-14 day threshold is the key diagnostic criterion for persistent symptoms 1, 2
The exception is the severe onset pattern (high fever + purulent discharge from onset), which can be diagnosed earlier 1, 4, 3
Imaging Is NOT Recommended for Routine Diagnosis
Do not obtain imaging studies (plain films, CT, MRI, or ultrasound) to distinguish bacterial sinusitis from viral URI 1, 2:
- Sinus abnormalities appear in 68% of children with viral URI and 42% of healthy children 1
- 87% of young adults recovering from a cold show maxillary sinus abnormalities on CT 1
- Imaging has high false-positive rates and does not change management in uncomplicated cases 1
- Reserve imaging only for suspected complications (orbital involvement, intracranial extension) or recurrent/chronic disease 2
Common Diagnostic Pitfalls to Avoid
Purulent nasal discharge alone is not diagnostic 1, 5:
- The quality of nasal discharge changes during normal viral URIs 1
- The key is persistence of purulent discharge beyond 10 days, not just its presence 1, 2
Physical examination findings are nonspecific 1:
- Erythema and swelling of nasal turbinates occur with both viral and bacterial infections 1
- No single sign or symptom has strong diagnostic value 1
Consider underlying predisposing factors 1, 2:
- Allergic rhinitis is the most common predisposing factor 2
- In children, nasal polyps should prompt evaluation for cystic fibrosis 2
- Other factors include anatomic obstruction, immunodeficiency, and ciliary dysfunction 1
Differential Diagnosis to Consider
Rule out these conditions that mimic bacterial sinusitis 1, 4:
- Allergic rhinitis: Clear discharge, nasal/ocular pruritus, sneezing, seasonal pattern 4
- Prolonged viral URI: Symptoms typically improve by day 10 1, 2
- Migraine: Can be differentiated by absence of purulent discharge and fever 1, 4
When to Suspect Complications
Immediately evaluate for complications if any of these are present 2, 5: