Clinical Inquiries

Do imaging studies aid diagnosis of acute sinusitis?

Reider JM, Nashelsky J, Neher JO. J Fam Pract. 2003 Jul;52(7):565-7; discussion 567

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-based 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:

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.

Clinical Commentary

In acute bacterial sinusitis, the history and physical have somewhat limited sensitivity and specificity. Unfortunately, imaging studies add little valuable information. Primary care physicians must therefore be reconciled to some degree of diagnostic error.

The risks associated with under-diagnosis are small, since most cases of mild sinusitis will resolve spontaneously without treatment. The risks of over-diagnosis include increased antibiotic costs, side effects, allergic reactions, and the development of resistant organisms. It is prudent, therefore, to make the diagnosis only when multiple suggestive historical and exam elements are present and to avoid giving antibiotics to patients with mild, nonspecific illnesses.

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 Institute for Clinical Systems Improvement recommends that radiology be used only if initial treatment has failed, and notes that a primary goal of its guideline was to reduce the number of x-rays that physicians order for this diagnosis.16

The American College of Radiology’s criteria for sinusitis in the pediatric population ranked several radiographic studies based on their appropriateness for given clinical conditions. This review17 suggests that no imaging is appropriate if symptoms have persisted <10 days. For patients with symptoms lasting >10 days and with persistent fever, CT scan is recommended.

Figures

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

References

  1. Berg O, Carenfelt Cnull Analysis of symptoms and clinical signs in the maxillary sinus empyema. Acta Otolaryngol. 1988. Volume 105. Page(s): 343-349.
  2. Williams JW, Simel DL, Roberts L, Samsa GPnull Clinical evaluation for sinusitis. Making the diagnosis by history and physical examination. Ann Intern Med. 1992. Volume 117. Page(s): 705-710.
  3. No author listed. Clinical practice guideline: management of sinusitis. Pediatrics. 2001. Volume 108. Page(s): 798-808.
  4. Snow V, Mottur-Pilson C, Hickner JMnull Principles of appropriate antibiotic use for acute sinusitis in adults. Ann Intern Med. 2001. Volume 134. Page(s): 495-497.
  5. Lau Jnull Diagnosis and treatment of acute bacterial rhinosinusitis. Evidence Report/Technology Assessment No. 9. Rockville, MD: Agency for Health Care Policy and Research; 1999..
  6. Varonen H, Makela M, Savolainen S, Laara E, Hilden Jnull Comparison of ultrasound, radiography, and clinical examination in the diagnosis of acute maxillary sinusitis: a systematic review. J Clin Epidemiol. 2000. Volume 53. Page(s): 940-948.
  7. Lindbaek M, Hjortdahl Pnull The clinical diagnosis of acute purulent sinusitis in general practice: a review. Br J Gen Pract. 2002. Volume 52. Page(s): 491-495.
  8. Lindbaek M, Hjortdahl P, Johnsen ULnull Use of symptoms, signs, and blood tests to diagnose acute sinus infections in primary care: comparison with computed tomography. Fam Med. 1996. Volume 28. Page(s): 183-188.
  9. Lindbaek M, Johnsen UL, Kaastad Eet al. CT findings in general practice patients with suspected acute sinusitis. Acta Radiol. 1996. Volume 37. Page(s): 708-713.
  10. Benninger MS, Sedory Holzer SE, Lau Jnull Diagnosis and treatment of uncomplicated acute bacterial rhinosinusitis: summary of the Agency for Health Care Policy and Research evidence-based report. Otolaryngol Head Neck Surg. 2000. Volume 122. Page(s): 1-7.
  11. Cotter CS, Stringer S, Rust KR, Mancuso Anull The role of computed tomography scans in evaluating sinus disease in pediatric patients. Int J Pediatr Otorhinolaryngol. 1999. Volume 50. Page(s): 63-68.
  12. Gordts F, Clement PA, Destryker A, Desprechins B, Kaufman Lnull Prevalence of sinusitis signs on MRI in a non-ENT paediatric population. Rhinology. 1997. Volume 35. Page(s): 154-157.
  13. Chong VF, Fan YFnull Comparison of CT and MRI features in sinusitis. Eur J Radiol. 1998. Volume 29. Page(s): 47-54.
  14. Patel K, Chavda SV, Violaris N, Pahor ALnull Incidental paranasal sinus inflammatory changes in a British population. J Laryngol Otol. 1996. Volume 110. Page(s): 649-651.
  15. No author listed. Joint Task Force on Practice Parameters in Allergy, Asthma and Immunology : Joint Task Force summary statements on diagnosis and management of sinusitis.
  16. No author listed. Acute Sinusitis in Adults. Bloomington, Minn: Institute for Clinical Systems Improvement (ICSI), 2002. Available at: www.icsi.org. Accessed on June 17, 2003..
  17. McAlister WH, Parker BR, Kushner DCet al. Sinusitis in the pediatric population. American College of Radiology. ACR Appropriateness Criteria. Radiology. 2000. Volume 215(Suppl). Page(s): 811-818.