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Diagnosing acute sinusitis

Reviews
Included studies
Results
Comment

Acute sinusitis is common enough, usually diagnosed by clinical examination, and treated with a course of antibiotics. The trouble is that many of the symptoms of acute sinusitis overlap with other common nasal complaints, so misdiagnosis and over-treatment with antibiotics is thought to be common. Diagnostic interventions of more invasive or high technology nature are available, like X-ray, CT scanning, or sinus puncture. So when two systematic reviews of diagnostic tests for the same condition appear in the same journal, almost adjacent to one another [1,2], clarity may be expected. Unfortunately, it's not quite like that, and another two brains problem rears its head. The clinical bottom line is that we don't have adequate diagnostic methods.

Reviews


The review from Boston [1] used a MEDLINE search for studies that had to compare the ability of at least two tests to diagnose acute sinusitis. This review included some studies despite an inadequate description of eligibility criteria, for sensible reasons. The sensitivity and specificity of one test had to be compared with another, reference, test. The main analytical tool was the summary receiver operating characteristics curve, when sensitivity is plotted against 1-specificity.

The review from Helsinki, Oulu and Copenhagen [2] also searched MEDLINE, and a Finnish database, and hand searched four journals and contacted experts in the field. Studies with the reference standard of sinus puncture or CT scanning were accepted. Validity criteria from a Cochrane working group were used for validity, and excluded some studies that failed some of these criteria. Summary receiver operating characteristics were also used as an analytical tool, but likelihood ratios were also produced.

Included studies


Review 1 included 13 studies, six with patients from a hospital or emergency room setting, three from general practice, one from both, and three did not say how patients were recruited. Review 2 included nine studies, eight of which were included in review 1 (though there were differences between the reviews in, for instance, the year of publication of studies with otherwise identical references, as well as internal inconsistencies).

Results


Review 1 describes and criticises the studies and the methods, and gives overall curves for several different comparisons. Review 2 also criticises the included trials, and gives prevalence, sensitivity, specificity and likelihood ratios for each method compared with sinus puncture (Table). Using the weighted prevalence figure and the likelihood ratios, radiography, ultrasound and clinical examination fail to generate post-test probabilities of more than 80% or less than 20%.

Table: Diagnostic methods for acute sinusitis, compared with sinus puncture

Comparison (with sinus puncture) Number of studies Number of patients Weighted prevalence (%, range) Positive likelihood ratio Negative likelihood ratio
Radiography 7 996 57 (26-80) 3.4 0.26
Ultrasound 7 940 56 (27-80 2.8 0.30
Clinical examination 2 245 46 (44-48) 3.3 0.40

Comment


These are cracking reviews, of high quality, and well written. Bandolier marginally prefers review 2 because it allows the calculation of post-test probabilities, and shows clearly how radiography, ultrasound and clinical examination fail to provide sufficiently high post-test probabilities to be truly useful: no better than 80% or 20% is probably not good enough. Review 1, though, has more details about the individual studies and the components of the diagnostic tests, so that is more useful in understanding what is going on.

Both have excellent discussions of the problems of diagnostic test reporting, and the particular problems about diagnosis of acute sinus infection, including those of sinus puncture, regarded as the gold standard. Taken together, these illuminate the problems of diagnostic test methods and quality, and their review. They both conclude, rightly, that it's back to the drawing board. Review 2 additionally adds the visionary concept of combining the two aspects of clinical management, diagnosis and treatment, as a unit.

Diagnostic testing evidence is in short supply. The importance of this particular topic lies in the opportunities for research across the primary and secondary care boundaries, and combining clinical examination with high-tech approaches.

References:

  1. EA Engels, N Terrin, M Barza, J Lau. Meta-analysis of diagnostic tests for acute sinusitis. Journal of Clinical Epidemiology 2000 53: 852-862.
  2. H Varonen, M Mäkelä, S Savolainen, E Läärä, J Hilden. Comparison of ultrasound, radiography, and clinical examination in the diagnosis of acute maxillary sinusitis: a systematic review. Journal of Clinical Epidemiology 2000 53: 940-948.
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