Acute respiratory tract infections are the reason for about a quarter of all visits to family doctors in North America, and a quarter of these visits are for acute sore throat.1
The large number of sore throats means that they account for 3% to 6% of all office visits.2,3
In adults, 85% to 90% of sore throats are caused by viral infections.4
Treating patients who have sore throats with antibiotics does not relieve symptoms very much, if at all. A study of patients with tonsillitis in 17 countries found that the mean duration of fever was 2 to 3 days, regardless of whether or not patients took penicillin.5
Patients who test positive for group A β-hemolytic streptococcus (GABHS) who are treated with penicillin have relief of symptoms about 16 hours earlier than those who test negative for GABHS.6
Treated or not, 85% of patients are completely free of symptoms at 1 week.7
Mentioning a sore throat to a doctor almost guarantees a prescription for antibiotics. In Australia, 89% of patients with sore throats got antibiotic prescriptions8
; in the United States, the rate was 73%.9
A study of 73 Newfoundland family doctors found that 84% of them prescribed antibiotics to adults with sore throats.10
In Holland, which has a tradition of low prescribing rates for antibiotics, the rate was still 52%.11
Attempts have been made to derive simple sore throat decision rules (STDR) so that doctors can more appropriately prescribe antibiotics for patients likely to have GABHS. In general, 4 clinical features have been found useful in deciding which adults are most likely to have GABHS infection: fever, tonsillar exudates, anterior cervical lymphadenopathy, and the absence of cough (12
). A Canadian study found that using clinical rules would have reduced prescriptions for antibiotics among adults with sore throats by 88%13
if doctors had followed these rules. Another study showed that, while using the rules improved physicians’ estimates of the presence or absence of GABHS, it did not alter how they used antibiotics.14
We wanted to know whether using STDR would change doctors’ antibiotic prescribing practices appropriately.
Sore throat decision rules used in our study
Rapid antigen detection tests (RADT) provide results much more quickly than the criterion standard of GABHS detection, agar plate culture, does. Rapid antigen detection tests have a specificity in the 95% range, so false-positive results are rare.15
The sensitivity of RADT increases with the number of positive clinical features a patient has.16
The primary advantage of RADT over throat-swab cultures is that results can be available in only 5 to 10 minutes, and the test costs as little as $5. Treatment, if needed, can be started before patients leave the doctor’s office.
A literature review using the terms “rapid antigen test,” “streptococcal sore throat,” and “primary care” found that RADTs have been used in various parts of the world: Denmark,17
the Canary Islands,20
In general, these studies concluded that the RADT was a valid test for diagnosing streptococcal sore throat in adults and that it had high specificity and positive predictive values. The value of RADT for children was less clear.
Using either STDR or RADT should allow family doctors to make rapid and more informed decisions than when they use usual clinical judgment. The objectives of this trial were to compare rates of diagnosis of likely GABHS infection, represented by prescriptions for antibiotics, using usual clinical judgment, STDR, RADT, and both STDR and RADT, and to assess whether STDR and RADT are better used alone or in combination.