Abstract
BackgroundRadiographs are the main outcome measure in epidemiological studies of osteoarthritis (OA). Ultrasound imaging has unique advantages in that it involves no ionising radiation, is easy to use and visualises soft tissue structures. Our objective was to measure the inter-rater reliability and validity of ultrasound imaging in the detection of features of knee OA.MethodsEighteen participants from a community cohort, had both knees scanned by two trained musculoskeletal sonographers, up to six weeks apart. Inter-rater reliability for osteophytes, effusion size and cartilage thickness was calculated by estimating Kappa (κ) and Intraclass correlation coefficients (ICC), as appropriate. A measure of construct validity was determined by estimating κ between the two imaging modalities in the detection of osteophytes.ResultsReliability: κ for osteophyte presence was 0.77(right femur), 0.65(left femur) and 0.88 for both tibia. ICCs for effusion size were 0.70(right) and 0.85(left). Moderate to substantial agreement was found in cartilage thickness measurements. Validity: For osteophytes, κ was moderate to excellent at 0.52(right) and 0.75(left).ConclusionSubstantial to excellent agreement was found between ultrasound observers for the presence of osteophytes and measurement of effusion size; it was moderate to substantial for femoral cartilage thickness. Moderate to substantial agreement was observed between ultrasound and radiographs for osteophyte presence.
Highlights
Radiographs are the main outcome measure in epidemiological studies of osteoarthritis (OA)
The epidemiological study of knee osteoarthritis (OA) has had many barriers; a major problem being the definition of knee OA
Moderate to substantial agreement was found in cartilage thickness measurements except for the lateral femoral cartilage thickness on the right, which had a raw value of 0.06
Summary
Radiographs are the main outcome measure in epidemiological studies of osteoarthritis (OA). Ultrasound imaging has unique advantages in that it involves no ionising radiation, is easy to use and visualises soft tissue structures. The most commonly used outcome measure in studies of OA has been radiological criteria, such as those described by Kellgren and Lawrence [1]. Radiographs have limitations, such as the need for lowlevel radiation exposure and the inability to view soft tissue structures and assess inflammation. It has the disadvantage of obtaining only two dimensional images from one or more views. It is not surprising that organisations such as OMERACT and OARSI are in the process of developing research agendas on the use of ultrasound in OA [14]
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