Intra-rater reliability of lower leg subcutaneous skin fold thickness derived from hand-held a-mode ultrasound

BACKGROUND: Ultrasound is an important tool to diagnose many clinical conditions. Yet hand-held devices may be prone to more data variability in part from the greater likelihood of human error. OBJECTIVE: Quantify intra-rater reliability of subcutaneous skin fold thickness from a hand-held ultrasound device. PARTICIPANTS: College-age subjects (18 men, 14 women) submitted to two sets of ultrasound subcutaneous skin fold measurements spaced (mean + sem) 10.6 + 2.2 days apart. Per measurement, they stood relaxed as ultrasound measured the subcutaneous skin fold thickness that covered their left leg's calf muscle group. Measurements occurred with a hand-held device (BodyMetrix Pro System BX2000; Livermore, CA) used in accordance with the manufacturer's guidelines. Four subcutaneous measurements were made 90 degrees apart (anterior, medial, posterior, lateral) at the portion of the left calf with the largest circumference. To assess intra-rater reliability, we used intraclass correlation coefficients, limits of agreement, coefficient of variation and the smallest real difference. RESULTS: Intra-rater reliability was high for most of our statistical tests. CONCLUSION: Despite the relatively long period between measurements, our hand-held ultrasound device exhibited a high degree of intra-rater reliability. Given our results, ultrasound measurements may be a useful tool to quantify skin fold thickness.