Why does the Joint Commission insist on throat cultures when there’s been a negative quick strep test?
Several years ago, during the last Joint Commission survey of our hospital lab, we got dinged because we failed to routinely do a strep culture whenever a “quickie” strep screening test was negative. And we weren’t alone; I’ve heard from a colleague whose hospital got their wrist slapped for the same thing. The question is, what’s the rationale, and why is the JC so adamant?
Not too surprisingly, the instructions for your quickie strep screen test include some defensive language. The manufacturer suggests that a negative test be confirmed by a culture. The package inserts do not say that negative quickie tests must be confirmed by a strep culture, their instructions simply advise it. It would seem, therefore, that this advice could be taken or ignored, based on the discretion of the treating physician. Not according to the JC.
So the whole point of doing the quickie test – to get a rapid answer to a simple question – now becomes a big deal. Not only do patients (or their insurance companies) incur substantial additional charges for a culture that they didn’t want, but now you and your department have the hassle of following up on the culture results and advising the patient or parents of the results.
Clearly there is room for debate regarding the “cover the butt” recommendations of the makers of the quickie tests whereby they advise that a culture be obtained in the setting of a negative quickie test. Even the Infectious Disease Society of America, which typically wants to determine the etiologic cause of every infection it can get its hands on, does not agree with the recommendation of the package inserts. Specifically, in its 2002 guidelines (Bisno, et al,
Clinical Infectious Diseases, July 15, 2002) it is specifically stated that “because of the aforementioned features of acute pharyngitis in adults, exclusion of the diagnosis on the basis of negative RADT (rapid antigen detection test) results, without confirmation by negative culture results, is an acceptable alternative to diagnosis on the basis of throat culture results.”
Because of the increased prevalence of strep throats in children compared with adults, the IDSA does make a differentiation with regard to its recommendations regarding cultures in quickie-negative children and adolescents – but even here they allow some wiggle room, acknowledging that the quickie tests are getting more and more sensitive and may be approaching the gold standard – blood agar plate cultures (which are really not a true gold standard as noted below). Specifically the IDSA advise that physicians who use any RADT for diagnosis in children and adolescents and who do not use culture to confirm negative results should do so only after confirming in their own practice that the RADT has a sensitivity similar to that of throat culture.
Now remember that these recommendations of the IDSA are at least nine years old and that the sensitivity of quickie tests has to be getting better and better (the specificity has always been around 95% or greater). So, ask your lab director to do a little study comparing the sensitivity of your lab’s quickie test with that of some strep cultures.
To be fair, the Joint Commission is not entirely alone in their recommendations. The American Academy of Pediatrics has traditionally recommended strep cultures in children with negative quickie tests. So it appears that there is a distinction to be made between children and adolescents vs. adults with regard to recommendations regarding cultures based on age.
Fortunately, at least when it comes to adults, the use of follow-up cultures seems to be largely required just by the JC. In fact, there are some big guns that actively oppose the performance of throat cultures when quickie tests have a sensitivity exceeding 80% or more (which most do). In 1999 the CDC conveyed a series of expert panels to review the literature and make recommendations regarding a number of common respiratory infections. The recommendations were reviewed by a variety of professional societies and ultimately simultaneously published in a number of their journals.
The recommendations regarding pharyngitis (Cooper, R., et al, Ann Emerg Med, 37(6):711, June 2001) were endorsed by the American College of Emergency Physicians, the American Academy of Family Practice, the American College of Physicians and the CDC-P and they specifically state “throat cultures are not recommended for the routine primary evaluation of adults with pharyngitis or for the confirmation of negative results on rapid antigen tests when the sensitivity exceeds 80%.”
To put the yield of performing a throat culture in those adults with a negative quickie tests into perspective, it is noted in the Cooper paper that “to detect one additional case of GABHS infection, approximately 30 throat cultures would need to be performed on individuals who had at least two clinical signs suggestive of GABHS infection.”
Finally, it needs to be acknowledged that pharyngitis caused by GABHS is not highly prevalent in adults, it is certainly not life-threatening, it rarely has serious sequelae, it is self-limiting and is often over-treated in current practice.
When combined with the fact that throat cultures are, in fact, not truly the “gold standard” for strep throat infections and are subjected to a large number of sources of error (technique of swabbing, site of swabbing, the culture medium used, the conditions in which the culture is incubated and the inability to distinguish the carrier state from the true infection state), to deal with the hassle of performing cultures in adults with negative quickie strep tests just doesn’t make sense.
W. Richard Bukata, MD is the Editor of Emergency Medical Abstracts