Does This Patient Have Group A Strep Pharyngitis?
The numbers and costs are staggering. More than one-half billion people worldwide acquire group A streptococcal (GAS) pharyngitis annually.1 Although bacterial pharyngitis might be dismissed as a nuisance, it may lead to necrotizing fasciitis, rheumatic fever with cardiac sequelae, or glomerular disease.1 Conversely, patients with uncomplicated viral pharyngitis may be unnecessarily treated with antibiotics, and some may have severe allergic reactions.
Typically, a patient with a sore throat receives a cursory examination of the oropharynx and a quick decision about whether or not to use antibiotics. Unfortunately, diagnostic accuracy is thereby sacrificed.1 There has to be a better way. A 4-point scoring system, the Centor score,2 helps practitioners distinguish GAS from other types of pharyngitis (Table). There has also been one iteration of the Centor score, the McIsaac score,3 which also weighs the risk of GAS based on age (see Table). A recent “Top Paper” looks at the value of Centor and McIsaac scores in the setting of acute pharyngitis.1
PREDICTIVE POWER OF CENTOR AND McISAAC SCORES
For 206,870 persons who presented to a retail health chain with a sore throat, the scores were applied and the presence of GAS determined by testing. Results were as follows: for patients 15 years of age or older, 23% tested positive for GAS (7% of those with a Centor score of 0; 12%, Centor 1; 21%, Centor 2; 38%, Centor 3; and 57%, Centor 4). For patients 3 years of age or older, 27% tested positive for GAS (8% of those with a McIsaac score of 0; 14%, McIsaac 1; 23%, McIsaac 2; 37%, McIsaac 3; and 55%, McIsaac 4).1
OTHER CAUSES OF BACTERIAL PHARYNGITIS
Dr Centor provided an informed commentary on the results.4 He observed that both scores work best for pharyngitis in preadolescent children. Scoring for the presence of GAS in adolescents and adults is more controversial. In this problematic age group, other causes of pharyngitis include group C and other non-GAS infections, infectious mononucleosis, and Fusobacterium necrophorum infections (including Lemierre syndrome). So what, you may ask? Group C streptococcal infection can lead to glomerulonephritis and rheumatic fever. Most laboratories do not look for non-GAS, and F necrophorum is difficult to culture.
Dr Centor then offers sage advice. Since bacteria—GAS, non-GAS, and F necrophorum—cause an inflammatory response that is captured by the Centor and McIsaac scores (fever; exudate; swollen, tender nodes), a score of 3 or 4 should prompt therapy. Infections with GAS and the others will all be treated. The use of penicillin or a narrow-spectrum cephalosporin will result in less resistance.4
The approach to pharyngitis, especially in patients older than age 15, should always include a Centor or McIsaac score. The probability of bacterial pharyngitis with scores of 3 or 4 is greater than 80%. This makes the management of pharyngitis easier and evidence-based. It involves much more than GAS.
1. Fine AM, Nizet V, Mandl KD. Large-scale validation of the Centor and McIsaac scores to predict group A streptococcal pharyngitis. Arch Intern Med. 2012;172(11):847-852.
2. Centor RM, Witherspoon JM, Dalton HP, et al. The diagnosis of strep throat in the emergency room. Med Decis Making. 1981;1:239-246.
3. McIsaac WJ, White D, Tannenbaum D, Low DE. A clinical score to reduce unnecessary antibiotic use in patients with sore throat. CMAJ. 1998;158:75-83.
4. Centor RM. Adolescent and adult pharyngitis: more than “strep throat.” Arch Intern Med. 2012;172(11):852-853.
Dr Rutecki reports that he has no relevant financial relationships to disclose.