Diagnostic value and clinical validation of Acute Thyrotoxic Myopathy Symptom Score in acute thyrotoxic myopathy

Abstract

Objectives Acute thyrotoxic myopathy (ATM) is characterized by bulbar paralysis and limb myasthenia on the basis of hyperthyroidism, which can cause respiratory failure, coma and death. However, the diagnosis of ATM is challenging. The purpose of this study was to develop a symptom rating scale called the Acute Thyrotoxic Myopathy Symptom Score (ATMSS) to assist in the early diagnosis of ATM in clinical practice. Methods (1) the ATM reference sample was constructed by searching for patients diagnosed with ATM or thyrotoxic bulbar palsy in the PubMed, Embase and Web of Science databases (ATM cohort); (2) the ATMSS was formulated based on the ATM cohort after multidisciplinary discussion; and (3)51 patients with ATM and 49 patients with Graves' disease (GD) were enrolled in the study. (4) Receiver operating characteristic (ROC) curve analysis was applied to appraisal diagnostic value of the ATMSS for differentiating patients with ATM from patients with GD. (5) We also evaluated the correlation between ATMSS score and age, sex, thyroid function and thyroid-related antibody. Results The ATMSS score showed better diagnostic value at an optimal cut-off value of 5.5 [area under the curve (AUC) = 0.979; 95% confidence interval (CI) = 0.956-1; p < 0.0001; sensitivity = 94.1%; specificity = 93.9%]. The ATMSS score was positively correlated with free triiodothyronine (FT₃) [Spearman correlation coefficient (r_s) = 0.422, p < 0.001] and free thyroxine (FT₄) (r_s=0.497, p < 0.001). Conclusions We developed a symptom rating scale named the ATMSS, which is effective in diagnosing ATM, ATMSS score is positively correlated with thyroid function. ATMSS can be used as an additional tool for diagnosing ATM.