Centor score

The Centor score, and its age-adjusted modification known as the McIsaac score, are clinical prediction tools used to estimate the likelihood of group A beta-haemolytic streptococcal pharyngitis in patients presenting with acute sore throat.

They are intended to support antibiotic prescribing decisions and reduce unnecessary antimicrobial use in self-limiting illness.

Clinical context and use

The Centor and McIsaac scores are used in primary care, urgent care, and emergency settings when assessing patients with symptoms of acute pharyngitis or tonsillitis.

They estimate the probability that symptoms are due to streptococcal infection rather than viral illness and help stratify patients into groups where antibiotics are unlikely to help, may be considered, or are more likely to be beneficial.

In UK practice, these scores are often discussed alongside the FeverPAIN score, which is generally preferred in NICE guidance, although Centor-based scores remain widely recognised and used.

The original Centor score assigns one point for each of the following clinical features:

• Tonsillar exudate

• Tender anterior cervical lymphadenopathy

• History of fever

• Absence of cough

The total score ranges from 0 to 4.

The McIsaac score adjusts the Centor score to account for age, reflecting differences in streptococcal prevalence across age groups.

The age adjustment is applied as follows:

• Age 3–14 years: add 1 point

• Age 15–44 years: no adjustment

• Age 45 years or over: subtract 1 point

The total possible score therefore ranges from −1 to 5.

Lower scores indicate a low likelihood of streptococcal pharyngitis, where antibiotics are unlikely to provide benefit. Higher scores suggest an increasing probability of streptococcal infection.

As a general guide used in clinical practice:

• Scores of 0 or below indicate very low risk and support a no-antibiotic approach.

• Scores of 1–2 indicate low to intermediate risk, where antibiotics are usually not indicated and safety-netting is appropriate.

• Scores of 3 indicate moderate risk, where delayed antibiotic prescribing or further testing may be considered.

• Scores of 4–5 indicate higher risk, where immediate antibiotics may be appropriate.

Thresholds should always be applied alongside clinical judgement, patient factors, and local antimicrobial stewardship policies.

The Centor score was originally developed in adult emergency department populations. The McIsaac modification broadened applicability to children and primary care settings.

Evidence suggests that Centor-based scores can reduce unnecessary antibiotic prescribing when used as part of a structured assessment, although specificity is limited, particularly in low-prevalence settings.

Unlike FeverPAIN, the Centor and McIsaac scores do not include symptom duration or explicitly account for viral features such as coryza. This can reduce their discriminatory value in early presentations of sore throat.

For this reason, NICE guidance generally favours FeverPAIN in UK primary care, although Centor-based scores remain acceptable and are still widely used in practice and education.

Acute sore throat remains a common driver of antibiotic prescribing, despite most cases being viral and self-limiting.

The Centor and McIsaac scores support antimicrobial stewardship by providing a structured framework for decision-making, reducing variation in prescribing behaviour, supporting delayed prescription strategies, and helping clinicians explain management decisions.

Centor-based scores do not diagnose streptococcal infection and should not be used in isolation.

They should be applied cautiously in patients with immunosuppression, significant comorbidity, red flag symptoms such as airway compromise or systemic toxicity, recurrent or atypical presentations, or suspected complications such as peritonsillar abscess.

They are not designed to guide management of severe illness or complications.

Using a recognised scoring system can support documentation, audit, and shared decision-making. Recording the score may also help justify delayed or no-antibiotic strategies in line with antimicrobial stewardship principles.

Regardless of score, patients should receive clear advice on symptom control, expected illness duration, and when to seek further medical review.