From the Guidelines
The McIsaac score is a reliable clinical prediction rule for determining the likelihood of group A streptococcal pharyngitis in patients with sore throat, and its use can help reduce unnecessary antibiotic usage. The score assigns points based on five criteria: temperature ≥38°C, absence of cough, tender anterior cervical adenopathy, tonsillar swelling or exudate, and age, with a total score ranging from -1 to 5 [ 1 ]. The criteria for scoring include:
- +1 point for temperature ≥ 38 °C
- +1 point for absence of cough
- +1 point for tender anterior cervical adenopathy
- +1 point for tonsillar swelling/exudate
- +1 point for age < 15 years
- -1 point for age ≥ 45 years The management recommendations based on the score are:
- A score of 1 or less suggests that neither antibiotics nor culture are required
- A score of 2-3 indicates that a culture should be taken, and the antibiotic decision should be based on the result
- A score of 4 or more suggests that antibiotics should be initiated immediately or a culture taken [ 1 ]. This scoring system has been shown to have the potential to reduce unnecessary antibiotic usage in clinical practice [ 1 ].
From the Research
McIsaac Score Overview
- The McIsaac score is a validated scoring system used to determine the likelihood of an acute sore throat being caused by group A streptococcus (GAS) 2.
- The score is used to stratify patients who need strep testing and can help guide treatment decisions.
Calculation and Interpretation
- The McIsaac score ranges from 0 to 4, with higher scores indicating a higher likelihood of GAS pharyngitis 3.
- A score of 4 has been associated with positive GAS rates of 55% to 68% across different encounter types, including in-person and non-face-to-face visits 2.
- A score of 0 has been associated with a low risk of GAS pharyngitis, with none of the encounters with a score of 0 and no missing score components having a positive GAS test 2.
Comparison with Other Scoring Systems
- The McIsaac score is similar to the Centor score, which is also used to predict the risk of GAS pharyngitis 4, 3.
- Both scores have been validated in large-scale studies and can be used to guide testing and treatment decisions 3.
Clinical Application
- The McIsaac score can be used in non-face-to-face encounters, such as phone or electronic visits, to consider empiric treatment for GAS without testing if significant barriers to testing exist 2.
- The score can also be used to identify patients who are at low risk of GAS pharyngitis and may not require testing or treatment 5, 6.
- Penicillin and amoxicillin are recommended as first-line antibiotics for the treatment of GAS pharyngitis, with a recommended course of 10 days 4, 6.