Inter-observer Variability of Clinical Activity Score: Assessments in Patients With Thyroid Eye Disease

center dot PURPOSE: Thyroid eye disease (TED) can be difficult to manage. The range of available treatments is expand-ing rapidly; however, cost is a concern and some patients do not respond. The Clinical Activity Score (CAS) was devised as a measure of disease activity and a potential predictor of response to anti-inflammatory treatment. De-spite the widespread use of the CAS, inter-observer vari-ability has not been investigated. The aim of the study was to determine the inter-observer variability of the CAS in patients with TED. center dot DESIGN: Prospective reliability analysis. center dot METHODS: Nine patients with a spectrum of clinical features of TED were assessed by 6 experienced observers on the same day. Agreement among the observers was an-alyzed using the Krippendorff alpha. center dot RESULTS: The Krippendorff alpha for the total CAS was 0.532 (95% CI = 0.199-0.665), whereas alpha val-ues for the individual components of the CAS varied between 0.171 (CI = 0.000-0.334) for lid redness and 0.671 (CI = 0.294-1.000) for spontaneous pain. Assum-ing that a CAS value >3 implies suitability of the patient for anti-inflammatory treatment, the calculated Krippen-dorff alpha for agreement among assessors on whether treatment should be given or not given was 0.332 (95% CI = 0.0011-0.5862). center dot CONCLUSIONS: This study has shown unreliable inter -observer variability in total CAS and most individual CAS components, thus highlighting the need for improv- ing the performance of the CAS or seeking other meth-ods to assess activity. (Am J Ophthalmol 2023;252: 94-100. Crown Copyright (c) 2023 Published by Elsevier Inc. All rights reserved.)