Abstract 4113942: Validation of Changes in the Cutoff Values of Achilles Tendon Thickness on Radiography in the Clinical Criteria of Heterozygous Familial Hypercholesterolemia in Japan

Background: To increase sensitivity and maintain specificity, the 2022 Japan Atherosclerosis Society familial hypercholesterolemia (FH) clinical criteria was modified. In particular, the cutoff value of Achilles tendon thickness (ATT) on radiography was changed from ≥9 mm in both men and women to ≥8.0 mm in men and ≥7.5 mm in women. The current study aimed to validate the efficacy of this modification in independent samples. Methods: Patients with FH were retrospectively reviewed. The proportions of patients with pathogenic FH mutation who had an ATT of <7.5/8.0 mm (group 1), ≥7.5/8.0 and <9.0 mm (group 2), and ≥9 mm (group 3) were assessed. Results: In total, 492 patients were included in group 1, 102 in group 2, and 263 in group 3. Approximately 14.0%, 55.9%, and 79.8% of patients in groups 1, 2, and 3, respectively, exhibited FH mutation. Further, 37.3%, 77.3%, and 86.5% of patients with a low-density lipoprotein cholesterol level of ≥180 mg/dL in groups 1, 2, and 3, respectively, harbored FH mutation. Moreover, the median low-density lipoprotein cholesterol levels (157, 182, and 253 mg/dL, respectively) and the proportion of patients with protein-truncating mutation (3.8%, 16.7%, and 53.2%, respectively) had a significant trend. Conclusions: There was a substantial number of patients with FH who had an ATT of ≥7.5/8.0 and <9.0 mm. These patients previously had a deferred diagnosis of FH. However, they were diagnosed with FH based on the new clinical guideline.