| Streptococcal pharyngitis | |
|---|---|
| Classification and external resources | |
A culture positive case of streptococcal pharyngitis with typical tonsillar exudate in a 16 year old. |
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| ICD-10 | J02.0 |
| ICD-9 | 034.0 |
| DiseasesDB | 12507 |
| MedlinePlus | 000639 |
| eMedicine | med/1811 |
Streptococcal pharyngitis, streptococcal tonsillitis, or streptococcal sore throat (known colloquially as strep throat) is a type of pharyngitis caused by a group A streptococcal infection.[1] It affects the pharynx including the tonsils and possibly the larynx. Common symptoms include fever, sore throat, and enlarged lymph nodes. It is the cause of 37% of sore throats among children.[2]
Strep throat is a contagious infection, spread through close contact with an infected individual. A definitive diagnosis is made based on the results of a throat culture. However, this is not always needed as treatment may be decided based on symptoms. In highly likely or confirmed cases, antibiotics are useful to both prevent complications and speed recovery.[3]
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The typical symptoms of streptococcal pharyngitis are a sore throat, fever of greater than 38 °C (100 °F), tonsillar exudates (pus on the tonsils), and large cervical lymph nodes.[3]
Other symptoms include:
The incubation period and thus the start of symptoms for strep throat is between one to three days post contact.[3]
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Strep throat is caused by group A beta-hemolytic streptococcus (GAS).[6] Other bacteria such as non–group A beta-hemolytic streptococci and fusobacterium may also cause pharyngitis.[3][5] It is spread by direct, close contact with an infected person and thus crowding as may be found in the military and schools increases the rate of transmission.[5][7] It has been found that dried bacteria in dust are not infectious, although moist bacteria on toothbrushes or similar items can persist for up to fifteen days.[5] Rarely, contaminated food can result in outbreaks.[5] Of children with no signs or symptoms 12% carry GAS in their pharynx.[2]
| Points | Probability of Strep | Management |
|---|---|---|
| 1 or less | <10% | No antibiotic or culture needed |
| 2 | 11–17% | Antibiotic based on culture or RADT |
| 3 | 28–35% | |
| 4 or 5 | 52% | Empiric antibiotics |
The modified Centor score is used to determine the management of people with pharyngitis. Based on 5 clinical criteria, it indicates the probability of a streptococcal infection.[3]
One point is given for each of the criteria:[3]
A throat culture is the gold standard[8] for the diagnosis of streptococcal pharyngitis with a sensitivity of 90–95%.[3] A rapid strep test (also called rapid antigen detection testing or RADT) may also be used. While the rapid strep test is quicker, it has a lower sensitivity (70%) and statistically equal specificity (98%) as throat culture.[3]
A positive throat culture or RADT in association with symptoms establishes a positive diagnosis in those in which the diagnosis is in doubt.[9] Asymptomatic individuals should not be routinely tested with a throat culture or RADT because a certain percentage of the population persistently "carries" the streptococcal bacteria in their throat without any harmful results.[9]
As the symptoms of streptococcal pharyngitis overlap with other conditions it can be difficult to make the diagnosis clinically.[3] Coughing, nasal discharge, diarrhea, and red, irritated eyes in addition to fever and sore throat are more indicative of a viral sore throat than of strep throat.[3] The presence of marked lymph node enlargement along with sore throat, fever and tonsillar enlargement may also occur in infectious mononucleosis.[10]
Tonsillectomy may be a reasonable preventative measure in those with frequent throat infections.[11][12] Three or more a year was seen as sufficient in 2003.[13] Watchful waiting is also appropriate.[11]
Untreated streptococcal pharyngitis usually resolves within a few days.[3] Treatment with antibiotics shortens the duration of the acute illness by about 16 hours.[3] The primary reason for treatment with antibiotics is to reduce the risk of complications such as rheumatic fever and retropharyngeal abscesses[3] and they are effective if given within 9 days of the onset of symptoms.[6]
Analgesics such as non-steroidal anti-inflammatory drugs (NSAIDs) and paracetamol (acetaminophen) help significantly in the management of pain associated with strep throat.[14] Steroids are also useful in this respect[6][15] as is viscous lidocaine.[16] Aspirin may be used in adults but is not recommended in children due to the risk of Reye's syndrome.[6]
The antibiotic of choice in the United States for streptococcal pharyngitis is penicillin V due to safety, cost, and effectiveness.[3] Amoxicillin is preferred in Europe.[17] In India, where the risk of rheumatic fever is higher, intramuscular benzathine penicillin G is the first choice for treatment.[6] Appropriate antibiotics decrease the average 3–5 day duration of symptoms by about one day, and also reduce contagiousness.[9] They are primarily prescribed out of a motivation to reduce rare complications such as acute rheumatic fever and peritonsillar abscess.[18] The arguments in favour of antibiotic treatment should be balanced by the consideration of possible side effects,[5] and it is reasonable to suggest that no antimicrobial treatment be given to healthy adults who have adverse reactions to medication.[18] Antibiotics are prescribed for strep throat at a higher rate than would be expected from its prevalence.[19] Erythromycin and other macrolides are recommended for people with severe penicillin allergies.[3] First, general cephalosporins may be used in those with less severe allergies.[3] Streptococcal infections may also lead to acute glomerulonephritis, however the incidence of this side effect is not reduced by the use of antibiotics.[6]
The symptoms of strep throat usually improve irrespective of treatment within three to five days.[9] Treatment with antibiotics reduces the risk of complications and transmission; children may return to school 24 hours after antibiotics are administered.[3]
Complications arising from streptococcal throat infections include:
Pharyngitis, the broader category into which Streptococcal pharyngitis falls, is diagnosed in 11 million people annually in the United States.[3] Although most cases are viral, group A beta-hemolytic streptococcus is the cause in 15–30% of the pharyngitis cases in children and 5–20% in adults.[3] Cases usually occur in late winter and early spring.[3]
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