Signs of Bacterial Sinusitis
Bacterial sinusitis should be diagnosed when purulent nasal discharge occurs with nasal obstruction or facial pain/pressure AND symptoms either persist ≥10 days without improvement, worsen after initial improvement at 5-7 days ("double-sickening"), or present severely with high fever (≥39°C) plus purulent discharge for 3-4 consecutive days. 1, 2
Three Diagnostic Patterns for Bacterial Sinusitis
The diagnosis requires one of three distinct clinical presentations 2, 3:
1. Persistent Illness (Most Common)
- Symptoms lasting ≥10 days without any improvement 1, 2
- This is the most common presentation but requires the longest observation period 2
- Approximately 60% of patients with symptoms persisting 10+ days show significant bacterial growth on sinus aspiration 1, 3
2. Worsening Course ("Double-Sickening")
- New symptoms or worsening after 5-7 days of initial improvement 1, 2, 3
- This allows for the earliest diagnosis at day 5-7 2, 3
- Characterized by new onset of fever, headache, or increased nasal discharge after initial improvement 3
3. Severe Onset
- High fever ≥39°C (102.2°F) with purulent nasal discharge for 3-4 consecutive days 1, 2, 3
- Can be recognized within the first 3-4 days of illness 2
- Patients typically appear ill and require differentiation from severe viral infections 3
Cardinal Symptoms
The cornerstone of diagnosis is purulent nasal drainage in the presence of nasal obstruction and/or facial pain, pressure, or fullness. 1
Primary Diagnostic Indicators
Three major symptoms are consistently identified across guidelines 1:
- Purulent nasal discharge (anterior, posterior, or both—cloudy or colored, not clear) 1
- Nasal congestion/obstruction/blockage 1
- Facial pain/pressure/fullness (anterior face, periorbital region, or diffuse headache) 1
Critical Diagnostic Rule
Purulent nasal discharge is essential—a diagnosis of bacterial sinusitis is unlikely in its absence, even when other cardinal symptoms are present. 1, 4 The specificity for bacterial disease increases dramatically when nasal obstruction or facial pain occurs in combination with purulent discharge 1, 4.
Supporting Symptoms
Additional symptoms that strengthen the diagnosis include 2, 5:
- Postnasal drainage 2
- Headache 2
- Cough 2
- Fever 2
- Malaise and fatigue 2
- Halitosis 2
- Hyposmia/anosmia (reduced/absent smell) 2
- Ear pressure or fullness 2
- Maxillary tooth pain (especially unilateral) 6, 5
Physical Examination Findings
Clinical signs on examination include 2:
- Sinus tenderness on palpation 2
- Mucosal erythema 2
- Purulent nasal secretions visible on examination 2
- Increased pharyngeal secretions 2
- Periorbital edema 2
- Unilateral maxillary sinus tenderness 6
However, physical examination findings have limited diagnostic value, with sensitivity of only 69% and specificity of 64% for predicting bacterial presence. 7, 4
Critical Pitfalls to Avoid
Colored Discharge Alone Is Not Diagnostic
Do not diagnose bacterial sinusitis based on colored nasal discharge alone. 2, 4 Mucopurulent secretions occur normally after a few days of viral infection and are not specific for bacterial disease 2. The quality of nasal discharge changes during uncomplicated viral URIs 3.
Duration Misconceptions
- Symptoms present for <10 days without worsening are unlikely to represent bacterial infection 4
- Cough and nasal drainage can persist 10+ days in 40% of uncomplicated viral infections 4
- Duration beyond 7 days is moderately sensitive but relatively nonspecific because it doesn't reliably distinguish prolonged viral infection from bacterial disease 3, 4
Fever and Mucus Color Are Not Differentiating
Neither nasal mucus color nor the presence of fever is useful in differentiating bacterial from viral disease. 1 Fever in viral URIs typically resolves within 24-48 hours, unlike bacterial sinusitis 4.
Imaging Is Not Indicated
Do not obtain radiographic imaging for patients meeting diagnostic criteria unless a complication or alternative diagnosis is suspected. 1, 2 Plain radiography is neither useful nor cost-effective 1. Sinus opacification is present in 87% of adults with acute viral URI symptoms, yet 79% show marked improvement after 2 weeks without antibiotics 4.
Pediatric Presentation Differences
In children, symptoms are similar but often include 2:
Diagnostic Algorithm
Step 1: Assess for purulent nasal discharge
- If absent → Do not diagnose bacterial sinusitis regardless of other symptoms 4
Step 2: Determine temporal pattern
- Symptoms ≥10 days without improvement → Persistent illness pattern 1, 2
- Worsening after 5-7 days of initial improvement → Double-sickening pattern 1, 2
- High fever ≥39°C + purulent discharge for 3-4 days → Severe onset pattern 1, 2
- Symptoms <10 days without worsening → Likely viral URI 3, 4
Step 3: Assess for combination of cardinal symptoms
- Purulent discharge + nasal obstruction or facial pain = highest specificity 1, 7
- Isolated nasal obstruction or facial pain without purulence = broad differential diagnosis 1
Step 4: Consider supporting features
- Unilateral facial/tooth pain increases likelihood 1, 6
- Bilateral symptoms without unilateral pain make bacterial sinusitis less likely 4
When to Suspect Complications
Evaluate for complications with imaging if any of the following are present 3: