Background: Clinical diagnosis of acute bacterial sinusitis (ABS) is a concern when a patient presents with nasal discharge of recent onset together with facial pain or pressure. Given this presentation, the doctor would benefit from having access to software that specifies, first, what diagnostic indicators experts typically use in that diagnosis and then, upon entry of those facts, what experts' typical probability of ABS is in such a case.
Methods: We specified a set of 23 hypothetical presentations of this type by patients 20-75 years of age, involving a comprehensive set of clinical-diagnostic indicators. Members of an international expert panel independently set the probability of ABS in each of these cases. A logistic function of the diagnostic indicators was fitted to the medians of the probabilities.
Results: The fitting led to an expression of the experts' median probability of ABS as a joint function of the duration of the patient's facial pain/pressure, and indicators of the location(s) of this; indicators of exacerbation of the pain/pressure on bending forward, nasal obstruction, maxillary and/or frontal tenderness, pus from middle meatus, purulent postnasal drip, and fever; and indicators of recent upper respiratory tract infection, nasal polyposis and status post sinus surgery. This probability function is accessible at http://www.evimed.ch/ABS.
Interpretation: That probability function, made readily accessible, provides for expertly probability setting in clinical diagnosis of ABS, relevant for decisions about further diagnostics or treatment without further tests.