This Centor score for strep pharyngitis calculator estimates the probability of streptococcal pharyingitis based on clinical data. There is in depth information about the diagnosis mean, positive and negative criteria below the form.
How does Centor score for strep pharyngitis calculator work?
This is a health tool that evaluates whether the pharyngitis in the patient’s presentation can be of streptococcal cause and makes recommendations on whether to pursue further testing or not.
The modified Centor criteria in the present diagnosis method is also known as the McIsaac score and correlates with risk of positive cultures through a series of percentages.
New IDSA guidelines recommend the pursuit of testing or throat culture before any antibiotic treatment is prescribed.
Criteria used in the Centor score for strep pharyngitis calculator is:
■ Age – a new addition in the modified version of the score with three different age groups, something that reflects the very low probability of GAS in children younger than 3 and in the elderly and the fact that the incidence of the sickness decreases with age.
■ Exudate or swelling on tonsils.
■ Tender/Swollen anterior cervical lymph nodes.
■ Fever more than 38C, 100.4F.
■ Cough present (if yes awarded 0 points, otherwise 1 point).
The presence of three or four of the clinical signs provides recommendation for further diagnosis of Group A beta-haemolytic streptococcus (GABHS) as a cause of presentation with a sore throat, with a 40 – 60% chance for the patient to require antibiotic treatment.
The absence of the clinical signs discussed above indicates a negative diagnosis in 80% of cases, therefore there is no need for antibiotic therapy.
National Institute for Health and Clinical Excellence (NICE) recommends antibiotic therapy in all cases with positive culture results and Centor score higher than 3.
The main criticism received by the Centor score concerns the fact that it might provide false negatives in some cases in which the symptoms are not exacerbated, therefore preventing patients from being given appropriate therapy at the right time.
Centor score interpretation
The five criteria used in the score are each given different weights depending on their presence or absence in the case of clinical presentation symptoms and of age group in the age criteria.
The results range between -1 to 5 points, each with different percentages of GABHS positive diagnosis:
|Centor score||Diagnosis probability||Further recommendation|
|4, 5||51 – 53%||Rapid strep testing/culture|
|3||28 – 35%||Consider strep testing/culture|
|2||11 – 17%||Consider strep testing/culture|
|1||5 – 10%||No further testing|
|-1, 0||1 – 2.5%||No further testing|
Streptococcal pharyngitis guidelines
The standard diagnosis method for streptococcal pharyngitis remains the throat culture but the costs and delays in results make it a relatively pretentious method. At the same time, there is a high incidence of false positives which leads to unnecessary antibiotic treatments in cases with asymptomatic presentation for this type of upper respiratory tract infection.
Therefore CPR scores for GABHS pharyngitis such as the Centor score have been implemented to help with diagnosis.
The score is an incredibly useful tool in discerning the need for further testing as most pharyngitis cases are viral in origin and therefore do not respond to antibiotic treatment and the symptoms can be relieved through the use of steroids and NSAIDS. On the other hand, culture-confirmed Streptococcal infections, occurring in 5 to 17% of cases, require antibiotics.
In the US and UK, antibiotic recommendations concern patients with group A β-haemolytic streptococcal (GABHS) pharyngitis.
Proper antibiotic therapy reduces complication risk, relieves the symptoms and stops the spread of the disease. Some of the complications include: peritonsillar abscess, bacteraemia, acute glomerulonephritis and rheumatic fever.
1) Centor RM, Witherspoon JM, Dalton HP, Brody CE, Link K. (1981) The diagnosis of strep throat in adults in the emergency room. Med Decis Making; 1(3):239-46.
2) McIsaac WJ, White D, Tannenbaum D, Low DE. (1998) A clinical score to reduce unnecessary antibiotic use in patients with sore throat. CMAJ; 158(1):75-83.
3) Fine AM, Nizet V, Mandl KD. (2012) Large-Scale Validation of the Centor and McIsaac Scores to Predict Group A Streptococcal Pharyngitis. Arch Intern Med; 172(11): 847–852.
4) Aalbers J, O’Brien K, et al. (2011) Predicting streptococcal pharyngitis in adults in primary care: a systematic review of the diagnostic accuracy of symptoms and signs and validation of the Centor score. BMC Medicine (9):6703 Mar, 2016