GABHS has a number of known problematic sequelae that are the primary reason we look for it. Although rare, ARF (Acute Rhematic Fever) or Rheumatic Heart Disease is our primary concern. It is a sterile Type II autoimmune attack on the heart valves, myocardium, and joints resulting from the protracted high anti strep circulating antibodies. It is my understanding that if you treat Strep within 9 days you avoid this possibility. Apparently you need to treat about 40,000 cases of strep throat to avoid one such case. With the incidence of a severe allergic reaction to PCN being 1/12,000 so clinical judgement is paramount. The most winning strategy is to just use the “rapid test” as the decision maker. Using this strategy, in the US, we could prevent 85 cases of rheumatic heart disease annually at the cost of $727,000 per case prevented. You are actually more likely to contract Lemeirre’s Syndrome from Fusobacterium with a GABHS infection than Rheumatic Heart Disease.
Most experts agree that a rapid strep test is diagnostic. Follow up cultures for negative studies may be appropriate in younger patients. Cultures are never indicated under the age of 3 as they have not had enough antigenic exposure to develope Rheumatic Heart Disease.