Ultrasound imaging in women's arm flexor muscles: intra-rater reliability of muscle thickness and echo intensity.
Amilton Vieira, Angelina F Siqueira, João B Ferreira-Junior and 3 others
PMID 27683836WHAT IT FOUND
Ultrasound can track muscle thickness and echo intensity in young women's arm flexors, but changes under 2.82 mm or 10.23 echo intensity units may be measurement error.
Use these limits before calling a change real.
Key findings
01In 41 healthy young women, repeat ultrasound measurements of arm flexor muscle thickness and echo intensity showed very good agreement, with ICC values of 0.88.
02The reported smallest real difference values were 2.82 mm for muscle thickness and 10.23 arbitrary units for echo intensity.
03Muscle thickness and echo intensity were moderately and negatively correlated, and thickness explained 17% of echo intensity variability.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The findings apply only to healthy women aged 18 to 30 years, so they may not hold for older women, men, or people with injury or disease. Nine of the 50 recruited women did not return for the second assessment, so the reliability estimate is based on 41 participants. The same examiner captured the images, and that examiner had six months of ultrasound experience, so reliability may differ with less or more experienced clinicians. The study tested measurements at a marked site, 10 cm above the elbow crease, with a 7.5 MHz probe, so other sites, probe frequencies, or unmarked re-measurement may change the error. The paper reports intra-rater reliability, not how different clinicians would measure the same patient.
The easy way to misread this
Do not assume these ultrasound measurements can detect small changes in all patients. The reliability data come from 41 healthy young women, and changes smaller than 2.82 mm for muscle thickness or 10.23 arbitrary units for echo intensity may still be measurement error.