Diagnosing Bacterial Sinusitis in Adults

Bacterial sinusitis is diagnosed clinically when symptoms meet specific temporal and severity criteria, not by imaging or laboratory tests in uncomplicated cases. 1

Core Diagnostic Criteria: Three Clinical Patterns

The American Academy of Otolaryngology–Head and Neck Surgery establishes that acute bacterial rhinosinusitis (ABRS) is diagnosed when any one of the following patterns is present 1, 2:

Pattern 1: Persistent Symptoms (Most Common)

Purulent nasal drainage (anterior, posterior, or both) plus either nasal obstruction or facial pain/pressure/fullness lasting ≥10 days without improvement 1, 2
This is the most frequent presentation, but recognize that 98–99.5% of acute rhinosinusitis is viral and resolves spontaneously within 7–10 days 1, 3
The 10-day threshold distinguishes bacterial from viral infection, though purulent discharge alone cannot make this distinction 1

Pattern 2: Severe Presentation

High fever (≥39°C) with purulent nasal discharge and facial pain for ≥3–4 consecutive days at illness onset 1, 2
This pattern warrants immediate antibiotic consideration without waiting for the 10-day threshold 2, 4

Pattern 3: "Double Worsening" (Double Sickening)

Initial improvement from a viral upper respiratory infection followed by new onset or worsening of purulent drainage, nasal obstruction, facial pain, or fever within 10 days 1, 2
This biphasic course strongly suggests bacterial superinfection 2

Cardinal Symptoms Required for Diagnosis

All three cardinal features must be assessed 1:

Purulent nasal discharge (cloudy or colored, not clear) – reported by patient or observed on exam 1
Nasal obstruction/congestion – reported as blockage, stuffiness, or diagnosed on physical exam 1
Facial pain/pressure/fullness – anterior face, periorbital region, or diffuse/localized headache 1

Critical distinction: Facial pain/pressure in the absence of purulent nasal discharge is insufficient to diagnose acute rhinosinusitis 1

Physical Examination Findings That Support Diagnosis

Purulent secretions in nasal cavity or posterior pharynx (observed directly or by rhinolaryngoscopy) 2
Mucosal erythema and edema on nasal examination 2, 5
Tenderness to palpation or percussion over affected sinuses (maxillary, frontal) 2, 5
Unilateral maxillary sinus tenderness is particularly predictive of bacterial infection 1, 6
Hyponasal speech indicating nasal obstruction 1
Periorbital edema or dark circles beneath eyes 2

Nasal endoscopy provides superior visualization and can identify purulent drainage from the middle meatus, though it is not required for diagnosis in uncomplicated cases 2

Additional Signs and Symptoms (Supportive but Not Required)

Fever 1
Cough 1
Fatigue/malaise 1
Reduced or absent sense of smell (hyposmia/anosmia) 1
Maxillary dental pain 1
Ear fullness or pressure 1

Clinical Features That Increase Likelihood of Bacterial Infection

The following findings raise the probability of ABRS 4, 6:

Persistent purulent nasal discharge ≥7 days 4, 6
Maxillary tooth or facial pain (especially unilateral) 4, 6
Unilateral maxillary sinus tenderness on examination 4, 6
Worsening symptoms after initial improvement 4, 6
Unilateral facial pain that worsens when bending forward (suggests maxillary sinus involvement) 2

When Imaging Is NOT Indicated

Radiographic imaging (X-ray or CT) should NOT be obtained for patients meeting clinical diagnostic criteria for uncomplicated acute sinusitis 1, 2:

Clinical criteria have comparable diagnostic accuracy to sinus radiography 2
Plain radiographs have significant false-positive and false-negative results 2
Up to 87% of young adults recovering from a common cold show significant maxillary sinus abnormalities on CT, making findings nonspecific 2
Imaging is not cost-effective regardless of baseline sinusitis prevalence 2
Sinus radiography and ultrasonography are not recommended in uncomplicated cases 2, 6

When Imaging IS Indicated

CT imaging (without contrast) should be obtained only when complications or alternative diagnoses are suspected 1, 2, 5:

Orbital involvement (periorbital swelling, proptosis, visual changes, diplopia) 2
Intracranial complications (severe headache, altered mental status, cranial nerve deficits) 2
Facial swelling or erythema 2
Forehead swelling suggesting frontal bone involvement (Pott's puffy tumor) 2
Immunocompromised state (HIV, diabetes, chronic corticosteroid use) 2
History of facial trauma or surgery 2
Failure to respond to appropriate antibiotic therapy after 21–28 days 2, 5
Suspected alternative diagnosis (malignancy, fungal infection, granulomatosis with polyangiitis) 2, 5
Unilateral nasal septal ulceration (suggests destructive process, not simple rhinosinusitis) 5

Laboratory Testing: When and What to Order

Laboratory tests are NOT required for routine diagnosis of uncomplicated ABRS 1, 4. However, specific scenarios warrant testing:

Recurrent or Chronic Sinusitis (≥3 episodes/year or symptoms >8 weeks)

Quantitative immunoglobulin levels (IgG, IgA, IgM) 5
Specific antibody response testing to assess for underlying immunodeficiency 5
HIV testing if immunocompromised state is suspected 5

Suspected Systemic Disease (unilateral nasal ulceration, constitutional symptoms, weight loss)

Complete blood count with differential 5
Erythrocyte sedimentation rate (ESR) 5
C-reactive protein (CRP) 5
Chest radiograph to evaluate for pulmonary infiltrates, masses, or cavitary lesions 5

Distinguishing Viral from Bacterial Rhinosinusitis

Viral rhinosinusitis (VRS) is diagnosed when 1, 2:

Symptoms are present <10 days and not worsening 1, 2
Clear or cloudy drainage (not purulent) 2
Nasal congestion and facial pressure without severe features 2

Key point: Only 0.5–2.0% of viral upper respiratory infections progress to bacterial sinusitis 2. Most cases resolve without antibiotics within 7 days 1, 3.

Common Diagnostic Pitfalls to Avoid

Do NOT diagnose ABRS based on purulent nasal discharge alone – this reflects neutrophilic inflammation common to viral disease 1, 3
Do NOT prescribe antibiotics for symptoms <10 days unless severe features (fever ≥39°C with purulent discharge for ≥3 consecutive days) are present 1, 3
Do NOT obtain routine imaging for uncomplicated cases – up to 87% of viral URIs show sinus abnormalities on CT 2
Do NOT assume mucus color indicates bacterial infection – color reflects neutrophils, not bacteria 3
Do NOT diagnose "chronic sinusitis" without imaging and biopsy in patients with destructive nasal lesions 5

Special Considerations in Children

Children rarely have headache or facial tenderness 2
Persistent cough, irritability, and vomiting are more prominent symptoms 2
Nasal polyps in children should prompt evaluation for cystic fibrosis 2
Middle ear effusions and eustachian tube dysfunction frequently accompany acute sinusitis 2

Red Flags Requiring Urgent Evaluation

Immediate ENT referral or emergency evaluation is warranted for 2, 5:

Severe headache, visual changes, periorbital swelling/erythema 2
Proptosis, diplopia, altered mental status 2
Cranial nerve deficits 2
Unilateral nasal septal ulceration with constitutional symptoms 5
Weight loss, chronic productive cough (suggests systemic disease) 5

Summary Algorithm for Diagnosis

Assess symptom duration and pattern:
- <10 days without worsening → Viral rhinosinusitis (no antibiotics) 1, 2
- ≥10 days without improvement → Consider ABRS 1, 2
- Severe symptoms ≥3–4 days → Consider ABRS 1, 2
- Double worsening → Consider ABRS 1, 2
Confirm cardinal symptoms:
- Purulent nasal discharge plus nasal obstruction or facial pain/pressure 1
Perform focused physical exam:
- Look for purulent secretions, mucosal erythema, sinus tenderness 2, 5
Reserve imaging for complications or alternative diagnoses 1, 2
Reserve laboratory testing for recurrent/chronic cases or suspected systemic disease 5

How is bacterial sinusitis diagnosed in an otherwise healthy adult presenting with acute rhinosinusitis symptoms (nasal congestion, purulent nasal discharge, facial pain/pressure, and reduced sense of smell)?

Help us tailor your experience