Diagnostic accuracy is a factor neglected by most antimicrobial stewardship programs and should perhaps be subject to regular audit and feedback.  It is heavily dependent upon the context of the clinical contact – for example, time-pressured, after hours hospital ward patient encounters are prone to quick judgements and sloppy diagnoses.  For a persuasive discussion of broader diagnostic error issues and the need for a new paradigm was published in 2013, BMJ by Gordon Schiff.  

A landmark just published US study in ICHE by Felice et al  has shown that even with decision support software, many antimicrobial courses were inappropriate due to inappropriate initial diagnosis of infectious or potentially infectious conditions. A review of 501 antimicrobial courses showed 62% correct diagnosis, 31% clearly incorrect and 4% indeterminate. There was much greater disagreement between clinicians and reviewers for urinary tract infections (comprising cystitis, pyelonephritis or urosepsis) and pneumonia than abscesses or wound infections. For all the cases the accuracy of the initial diagnosis was associated with the quality of the clinical evidence available to the clinician at the time.

The appropriateness of antimicrobial courses was strongly associated with the level of diagnostic accuracy. Appropriate antimicrobials were prescribed in 62% of cases where the diagnosis was correct and only 5% of the incorrect or indeterminate diagnoses. Antimicrobial prescriptions where also more likely to be inappropriate or not needed when clinicians were treating a sign or symptom rather than a syndrome or disease.

Many factors were identified as contributing to poor diagnostic accuracy. These included decision making processes, diagnosing conditions not related to the reason for admission, fear of bad outcomes from serious infections and lack of adherence to diagnostic criteria.

This study shows how important the right diagnosis is for getting the antimicrobial prescription right. The study identified that little to no feedback is given to clinicians regarding incorrect diagnoses. There is also a suggestion that antimicrobial stewardship programs could increase their effectiveness by helping clinicians make the initial diagnosis and helping inform when antimicrobials could be withheld.

For more along these lines:

• A further review of the new study study 
• International society devoted to improving diagnosis in medicine.