EVIDENCE-BASED ANSWER
Accurate diagnosis of acute sinusitis in both children and adults depends on the history and clinical examination of the patient. While the clinical signs and symptoms of acute sinusitis are often difficult to distinguish from viral upper respiratory infection,1,2 such an assessment remains the best approach to diagnosing acute sinusitis (strength of recommendation [SOR]: A). There is no role for imaging in the diagnosis of acute sinusitis. For patients who have persistent symptoms, or those for whom surgery is being considered, some guidelines suggest that coronal computed tomography (CT) scan of the paranasal sinuses be considered (SOR: C, expert opinion).
Evidence summary
Three recent evidence-based guidelines3,4,5 suggest that children and adults with acute sinusitis may benefit from treatment with antibiotics more than those with rhinitis. Clinicians must develop a strategy for accurately diagnosing sinusitis to make sound treatment decisions. In the absence of a clear diagnosis of acute sinusitis, antibiotics are very unlikely to improve symptoms and are, therefore, not indicated.
Clinical evaluation. Berg1 studied 150 patients with clinical diagnoses of sinusitis and found that 85% of them had positive sinus puncture. In a review of the 11 studies that met evidence-based inclusion criteria, Varonen6 concluded that clinical evaluation has a sensitivity of roughly 0.75, whereas radiographic methodologies have sensitivities >0.80. In a prospective trial and subsequent review of the literature, Lindbaek7,8,9 suggests that several key clinical signs and symptoms can provide a level of sensitivity that approaches that of CT or magnetic resonance imaging (MRI), while enhancing specificity:
- Purulent secretion reported as a symptom or found in the nasal cavity by the doctor
- Pain in the teeth
- Pain on bending forward (inconsistent findings between studies)
- Two phases in the illness history
- Elevated erythrocyte sedimentation rate or increased C-reactive protein
- Symptoms for at least 7 days
Lau and colleagues5,10 reviewed 14 studies that compared various imaging studies with clinical evaluation or sinus puncture and aspiration with culture or both. A positive aspirate for bacterial pathogens was defined as the gold standard for diagnosis of sinusitis (Table).
X-ray vs sinus puncture. Depending on the criteria used to define a diagnosis of sinusitis on plain radiograph, estimates of sensitivity in these studies ranged from 0.41 to 0.90, and specificity estimates ranged from 0.61 to 0.85. Imaging studies that included “mucous membrane thickening” as a criterion for sinusitis were more sensitive but less specific than studies defining positive radiographs as “opacification of sinus.”
CT scan, MRI, ultrasound. While a CT scan is more sensitive than plain x-ray film,11 and MRI is more sensitive than a CT scan,12,13 the specificity of these studies is unclear. For example, in children and adults without symptoms of sinusitis, the prevalence of sinusitis signs on CT and MRI is 45% and 42%, respectively.6,7,14 In light of such findings, these imaging methodologies are better reserved for patients in whom surgery is being contemplated, or for whom chronic sinusitis is a concern. In the 1980s and 1990s, ultrasound was studied enthusiastically. Variability in test performance is great.6 Since the cost of this procedure is similar to that of a sinus CT, ultrasound is not indicated in the diagnostic evaluation of the sinuses.
Though the sensitivity and specificity of a clinical evaluation possibly could be enhanced with the use of imaging studies, diagnostic accuracy of acute disease is not sufficiently improved to justify the cost or inconvenience of such interventions.
TABLE
Sensitivity and specificity of imaging modalities in sinusitis
| Diagnostic technique | Sensitivity | Specificity |
|---|---|---|
| X-ray | Variable | Variable |
| CT scan | High | Poor |
| MRI | High | Poor |
| Sinus puncture | High | High |
| Clinical evaluation | High | Moderate |
Recommendations from others
In a guideline on appropriate antibiotic use in sinusitis,4 endorsed by the Centers for Disease Control and Prevention, American Academy of Family Physicians, the American College of Physicians–American Society of Internal Medicine, and the Infectious Diseases Society of America, radiography is not recommended for the diagnosis of acute sinusitis. The guideline recommends that clinicians rely on duration of illness (at least 7 days) and severity of symptoms to make an accurate diagnosis of sinusitis.
The American Academy of Allergy, Asthma and Immunology15 guideline makes the following recommendations regarding imaging:
- The use of imaging may be appropriate when there are vague symptoms, or poor response to initial management
- Standard radiographs are insensitive, but may be used for diagnosis of acute sinus disease
- CT is preferred for preoperative evaluation of the nose and paranasal sinuses
- MRI is very sensitive for diagnosis of soft tissue disease in the frontal, maxillary, and sphenoid sinuses
- Ultrasonography has limited utility but may be applicable in pregnant women and for determining the amount of retained secretions.