This is an observational cross-sectional study. This study included 194 wrists recruited from the outpatient clinics of Ain Shams University hospitals including diabetic patients not complaining from symptoms of CTS, patients presenting with symptoms of CTS and healthy controls. Participants were included if they were more than 18 years old. Participants presenting with symptoms of CTS were excluded if they had history of diabetes mellitus, thyroid disorder, renal or hepatic disorders, rheumatoid arthritis, gouty arthritis, chemotherapy intake, direct trauma to upper limb, symptoms suggestive of peripheral neuropathy or current pregnancy. All participants were divided according to clinical assessment by Arabic version of Boston carpal tunnel questionnaire (BCTQ) [7] to normal BCTQ (≤ 19) and abnormal (> 19). Subjects with normal BCTQ were divided into diabetics and non-diabetics. Median nerve area was measured using ultrasound (Esaote, MyLab Five, Italy). Linear 5–12 MHz probe was placed on distal wrist between pisiform bone medially and scaphoid bone laterally to provide short-axis view of median nerve at its inlet to carpal tunnel. CSA of median nerve was measured from inner border of epineurium (Fig. 1). Subjects with abnormal BCTQ were subjected to neurophysiological studies and were divided into mild, moderate and severe [5]. Written informed consent was obtained from participants.
Statistical analysis
Descriptive data were represented as mean and standard deviation for continuous variables and as number and percentage for categorical ones. Comparisons were made between groups using T test. Receiver operating characteristics (ROC) with area under the curve (AUC) analyses were used to detect the sensitivity and specificity of cut-off value of median nerve diameter measured by US to determine its abnormality. The analysis was done on SPSS ver. 25(IBM SPSS, NY, USA, 2017). p < 0.05 was considered significant.