A prospective multicentre external validation study of the Liverpool Peritonsillar abscess Score (LPS) with a no-examination COVID-19 modification

Objectives Our primary aim was to validate the Liverpool Peritonsillar abscess Score (LPS) externally in a new patient cohort. Our secondary aim was to modify the LPS in the light of the COVID-19 pandemic to produce a no-examination variant for use in this instance. Design Prospective multicentre external validation study. Setting Six different secondary care institutions across the United Kingdom. Participants Patients over 16 years old who were referred to ENT with any uncomplicated sore throat such a tonsillitis or peritonsillar abscess (PTA). Main outcome measures Sensitivity, specificity, positive predictive value and negative predictive value for both the original LPS model and the modified model for COVID-19. Results The LPS model had sensitivity and specificity calculated at 98% and 79%, respectively. The LPS has a high negative predictive value (NPV) of 99%. The positive predictive value (PPV) was slightly lower at 63%. Receiver operating characteristic (ROC) curve, including the area under the curve (AUROC), was 0.888 which indicates very good accuracy. Conclusions External validation of the LPS against an independent geographically diverse population yields high NPV. This may support non-specialist colleagues who may have concerns about mis-diagnosing a PTA. The COVID-19 modification of the LPS has a similar NPV, which may be of use where routine oral examination is to be avoided during the COVID-19 pandemic.