Achilles Tendon Softness a New Tool to Diagnose FH
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Achilles tendon softness should be considered a new indicator of familial hypercholesterolemia, in addition to Achilles tendon thickness, researchers suggest.

In a cross-sectional study that measured Achilles tendon thickness and elasticity (i.e., softness), thickness was greater and elasticity was lower in subjects with familial hypercholesterolemia, compared with non-FH controls. The findings are published in JACC: Cardiac Imaging.

"We consider that measuring Achilles tendon softness in addition to the thickness may be beneficial for suspected FH patients whose Achilles tendon thickness is borderline or falls short of the cutoff value due to lipid-lowering treatment or younger age," author told.

"We hope that Achilles tendon elastography may encourage clinicians to diagnose FH more correctly and actively," he added.

Achilles tendon xanthomas are specific for FH, but can be difficult to detect. To date, ultrasonography has been used to assess Achilles tendon thickness (ATT) to diagnose patients with familial hypercholesterolemia.

The Japanese researchers thought that the softness of the Achilles tendon might also be an important indicator of FH.

"Local lipid accumulation in the Achilles tendon is often observed in FH patients, and so we hypothesized that AT softness could also be a useful quantitative index for diagnosing FH," the author said.

In addition to AT thickness, the researchers measured AT elasticity with sonoelastography in 115 genetically diagnosed heterozygous FH patients and 77 non-FH control subjects.

"Sonoelastography is a recently developed ultrasound-based technique that allows qualitative assessment of tissue elasticity, softness, hardness. This technique has been shown to be useful in the differential diagnosis of such diseases as breast cancer, prostate cancer, and liver cirrhosis," author explained. "Recently, it has also been used to evaluate the Achilles tendon in healthy and pathological situations, especially those due to sport-related injury."

Achilles tendon thickness was greater and its degree of softness, measured by the elasticity index, was lower in the genetically diagnosed FH group compared with the non-FH group, indicating that the AT of FH patients was thicker and softer than that of non-FH patients.

In addition, an inverse relation between the elasticity index and Achilles tendon thickness was observed only in FH patients, suggesting that the Achilles tendon of FH patients becomes softer as it becomes thicker.

"This inverse relationship remained robust after adjustment for age, sex, smoking history, body mass index, low-density-lipoprotein cholesterol, high-density-lipoprotein cholesterol, and log triglycerides," author said.

The group also conducted receiver operating characteristic (ROC) analyses for the diagnosis of FH. They determined that the cutoff values of Achilles tendon thickness to diagnose FH were 5.3 mm in women and 5.6 mm in men; and that the cutoff values of Achilles tendon softness to diagnose FH in women were 4.7 mm in both men and women.

"The combined use of the elasticity index cutoff value and those for Achilles tendon thickness improved the detection rate," author said.