Tuesday, July 5, 2016

To rapid strep test or not to rapid strep test?

- Jennifer Middleton, MD, MPH

My medical assistant will routinely ask me if I want a rapid strep test for patients presenting with sore throat. I'm pleased that she asks, because it doesn't seem that long ago that every patient who walked in the door with a sore throat got tested. As the authors of Common Questions About Streptococcal Pharyngitis review in the July 1 issue of AFP, only patients with an intermediate risk of strep pharyngitis should get a rapid strep test; point-of-care tools can help physicians quickly make that assessment.

The authors assert that:
Results from rapid antigen detection testing (RADT) should be used in conjunction with a validated clinical decision rule such as the modified Centor score or the FeverPAIN score. Patients at low risk of GABHS pharyngitis can be treated symptomatically, RADT should be ordered for those at intermediate risk, and empiric antibiotics are an option for those at high risk.
Unfortunately, the rapid antigen test for streptococcal pharyngitis is not perfect. A recent meta-analysis found a combined sensitivity for the various types of rapid strep tests of 80% (95th confidence interval [CI] 77-82%) for pediatric patients and 94% (95th CI 80-99%) for adult patients; for specificity, use of rapid tests in pediatric patients was 93% (95th CI 92-93%) and in adults was 69% (95th CI 54-81%). Because this test can result in either a false positive or a false negative result a significant minority of the time, it is most useful in patients with an intermediate pre-test probability of having strep pharyngitis. If you're clinically convinced that the patient does or does not have strep pharyngitis, this imperfect test shouldn't change your clinical management.

The AFP article authors review the scoring systems most commonly used to assess the pre-test probability of strep pharyngitis, the Centor score and the modified Centor score. Both of these clinical decision rule scores are available in several point-of-care applications ("apps") for smartphones and tablets: MediMath, Qx Calculate, and MDCalc all include the Centor and modified Centor scores, to name a few. Scrolling through the scores and risk calculators on these apps, I'm continually surprised by what I see; often, I'm reminded of something that I had once heard of, intended to use in my practice, and then promptly forgot about.

Since many of these calculators involve inputting basic clinical information, office staff could easily be trained to use them. Integrating them directly into an electronic health record (EHR) system makes a lot of sense, too - wouldn't it be useful if your EHR could calculate the Centor score based on the history and exam you've documented while assessing the patient?

Family Practice Management has an ongoing feature that uses the "SPPACES" criteria to rate the quality of medical apps; you can find the collection of their app reviews here if you're interested in learning more about what's available for your smartphone and/or tablet. Of course, you can also link to online reference calculators using the AFP home page "Favorites" feature if you prefer to work off your desktop or laptop computer.

How are you using point-of-care tools in your practice?

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