NBC News covered this useful-seeming innovation last week – a predictive score to help patients decide whether their sore throat might be caused by Group A Strep. It seems a quite reasonable proposition on the surface – if patients can receive guidance on their pretest likelihood of disease, they might rather not seek unnecessary medical care. For the 12 million physician visits every year for sore throat, putting a dent in this would account for sizable cost savings.
This study describes retrospective development of a “Home Score” for use by patients, based on a MinuteClinic database of 71,000 sore throat presentations for which a strep swab was performed. The authors split the data into a derivation and a validation set, and produced a complex mathematic scoring system, from 1 to 100, based off age, fever, cough, and biosurveillance data. Using a score of 10 as a cut-off, the validation set sensitivity was 99%, specificity was 1%, and the prevalence data used resulted in a validation negative predictive value of 87%. This NPV, the authors say, is the important number regarding advising patients whether they ought to seek care for GAS.
There are a few issues with this derivation, of course. First of all, the derivation population is subject to selection bias – as only patients with strep swabs are included. Then, the MinuteClinic data has to be generalizable to the remaining adult population. The use of the Home Score also depends on the availability of biosurveillance data for their specialized algorithm. Finally, their NPV cut-off of 90% would theoretically obviate clinic visits for only 230,000 of the 12 million patients seeking care for sore throat – a large drop, but only a drop in the bucket, nonetheless.
And, the elephant in the room: Group A Strep doesn’t need antibiotics in the United States. The likelihood of adverse reactions to treatment of GAS exceeds the chance of benefit – whether progression to peritonsilar abscess or rheumatic fever is considered. A few folks on Twitter chimed in to echo this sentiment when this story was discussed:
@embasic @DrLeanaWen @MDaware @NBCNewsHealth just need to redesign app to say “no you don’t” regardless of sx
— Anand Swaminathan (@EMSwami) November 10, 2013
There are legitimate reasons to visit a physician for sore throat – but, in the U.S., nearly all uncomplicated pharyngitis can safely stay home, GAS or not.
“Participatory Medicine: A Home Score for Streptococcal Pharyngitis Enabled by Real-Time Biosurveillance”
http://www.ncbi.nlm.nih.gov/pubmed/24189592