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Inter-observer Variability of Clinical Activity Score: Assessments in Patients With Thyroid Eye Disease
Petros Perros1, Miloš Žarković2, Simon H Pearce1
1From the Department of Endocrinology (P.P., S.H.P., S.R.), Royal Victoria Infirmary, Newcastle upon Tyne, UK; Translational and Clinical Research Institute (P.P., S.H.P., SR), Newcastle University, Newcastle upon Tyne, UK.
Purpose:
Thyroid eye disease (TED) can be difficult to manage. The range of available treatments is expanding 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. Despite the widespread use of the CAS, inter-observer variability has not been investigated. The aim of the study was to determine the inter-observer variability of the CAS in patients with TED.
Design:
Prospective reliability analysis.
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 analyzed using the Krippendorff alpha.
Results:
The Krippendorff alpha for the total CAS was 0.532 (95% CI = 0.199-0.665), whereas alpha values 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. Assuming that a CAS value ≥3 implies suitability of the patient for anti-inflammatory treatment, the calculated Krippendorff alpha for agreement among assessors on whether treatment should be given or not given was 0.332 (95% CI = 0.0011-0.5862).
Conclusions:
This study has shown unreliable inter-observer variability in total CAS and most individual CAS components, thus highlighting the need for improving the performance of the CAS or seeking other methods to assess activity.
