Rapid Strep to Throat Culture Reflex Testing - EHR Optimization

Posted by Josh Carleton on Jul 7, 2017 9:50:00 AM

In LIS Optimization, Epic Beaker, Lab - Microbiology, EHR Optimization

In this post, we outline the current guidelines from the Infectious Disease Society of America (IDSA) for Group A Streptococcal (GAS) pharyngitis testing and discuss how you can implement them in your LIS. This EHR optimization only requires a few minutes of build. 

Group A Streptococcal Pharyngitis Testing Guidelines

Rapid strep tests, while being very specific, have sensitivities that range only from 70% - 90% when compared to throat cultures streaked on blood agar.1 Given that, many labs across the US automatically reflex a throat culture after a negative rapid antigen detection test (RADT) to protect against any false negatives.  While the throat culture is undoubtedly the gold standard for testing, should all negative RADTs reflex a throat culture? Not necessarily, according to guidelines from Infectious Disease Society of America (IDSA). 

In the guidelines1, the authors state:

"Routine use of back-up throat cultures for those with a negative RADT is not necessary for adults in usual circumstances, because of the low incidence of GAS pharyngitis in adults and the risk of subsequent acute rheumatic fever is generally exceptionally low in adults with acute pharyngitis (strong, moderate)."

So, in short, given GAS pharyngitis and the risk of more serious sequelae is not very high in adults, the reflex to throat culture is not recommended. 

Looking to one of the preeminent reference labs in the nation, ARUP,  we see that they follow this guideline as well, as their test description notes:

"If the Streptococcus (Group A) Rapid test is negative and the patient is less than 18 years old, a culture will be added for confirmation."

So, they don't reflex a throat culture for patients less than 18 years old, which matches what the guidelines state:

" In children and adolescents, negative RADT tests should be backed up by a throat culture (strong, high)."

EHR  Optimization  for GAS Pharyngitis Testing

Building this out in your own EHR/LIS should be possible with some very simple rule logic that states:


 Though it depends on your LIS, you would likely accomplish the above with two rules - the first being one that would look to the negative result AND the patient's age and the second rule looking to NOT equal the same logic. If your rule engine allows custom logic, you can simply duplicate your first rule and say "NOT (critieria 1(result) AND criteria 2(age))" in the custom logic. You'd then plug these rules into your LIS. The first causing the throat culture reflex to fire and the second (if you opt to use it) to display a message alerting techs that even though a reflex didn't fire, the system is behaving as it should. The message could state something similar to the effect of, "Throat culture reflexes are not recommended for this patient population." 

To further improve this build, one could add an order-specific question to the rapid strep test that asks the ordering provider if they would like to automatically reflex a throat culture for any patient populations that might require it, overriding the recommendations. The guidelines indicate that there are certain scenarios where this would be acceptable. One could, of course, create a number of questions with all of the possible reasons that a reflex would be desired, but it is my opinion that one catch-all question should suffice to minimize order question fatigue for physicians. If pursuing this option, one would simply have to adjust their rule logic to state:



This new logic simply has the original AND conditions with an added OR condition that looks to the response to the order-specific question. 

If implementing the question, it would be wise to run reports after a month or so to see if the question is being abused. If it is, you may want to consider defaulting the response to the question to "No", adding additional help text that explains the recommendation a bit more, or reach out to physicians individually.

What do you think about the suggestions above? Let us know in the comments section below. Have any questions about the build? Feel free to reach out to me and we can discuss.

Reference #1 (Guidelines):  2012 Nov 15;55(10):e86-102. doi: 10.1093/cid/cis629. Epub 2012 Sep 9. (https://www.idsociety.org/uploadedFiles/IDSA/Guidelines-Patient_Care/PDF_Library/2012%20Strep%20Guideline.pdf)
Image: National Institute of Allergy and Infectious Diseases, National Institutes of Health (https://www.flickr.com/photos/nihgov/33894910235)

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