NEW YORK – Musculoskeletal ultrasound is emerging as a technique for early detection of gout and rheumatoid arthritis, Dr. Jonathan Samuels said in a discussion that included a review of recent studies published by other researchers.
To its advantage, musculoskeletal ultrasound (US) is noninvasive, painless, and does not require exposure to radiation or contrast material. Dynamic assessment allows multiple joints to be viewed quickly during one sitting. Compared with MRI, musculoskeletal ultrasound is less costly, does not require the patient to lie still for prolonged periods, and is suitable for the claustrophobic patient, said Dr. Samuels, a rheumatologist at NYU Langone Medical Center, at a rheumatology meeting sponsored by New York University.
According to the American College of Rheumatology Musculoskeletal Ultrasound Task Force, "a future for US in American rheumatology seems certain. The improved clinical assessments and patient outcomes arising from the use of US should augment American rheumatology practice." (Arthritis Care Res. 2010;62:1206-19).
Yet, not many rheumatologists have incorporated musculoskeletal ultrasound into their practices. When Dr. Samuels surveyed the meeting attendees, roughly 50% indicated by a show of hands that they had taken a course in musculoskeletal ultrasound and 75% said it should become a standard clinical tool – but only 10% said they routinely used ultrasound.
One reason may be that learning opportunities are relatively sparse, and credentialing has not yet been standardized. While most European rheumatology fellowships include training in musculoskeletal ultrasound, such training is not standard or required in the United States. The UltraSound School of North American Rheumatologists (USSONAR) provides a suggested curriculum and on-line teaching and guidance, mostly for fellows and attendings interested in teaching ultrasound. It also offers an annual competency exam. The ACR began offering intensive, 2-day introductory training courses in 2010, providing the fundamentals of musculoskeletal US for rheumatologists who want to integrate ultrasound into their practices. New this year is a 3-day intermediate course for rheumatologists who have performed 60-100 scans within the past 2 years and have taken at least one beginner-level course.
The American Institute of Ultrasound in Medicine (AIUM) released Training Guidelines for the Performance of Musculoskeletal Ultrasound Examinations, but the ACR has not fully accepted the guidelines. There is currently no official certification process for musculoskeletal ultrasound, but that may be about to change. In February 2012, the ACR voted to develop and take ownership of a certification exam.
Dr. Samuels summarized two of the studies that suggest musculoskeletal ultrasound may allow early detection and treatment of subclinical rheumatoid arthritis and gout.
In a study from the Diakonhjemmet Hospital in Oslo (Norway) (Ann. Rheum. Dis. 2011;70:176-9), patients with baseline wrist synovitis as detected with ultrasound were twice as likely to develop erosions at 12 months, while the risk was only 28% for those with baseline MRI marrow edema.
Musculoskeletal ultrasound also was successfully used to detect monosodium urate deposits in gout patients and in patients with asymptomatic hyperuricemia in a nonrandomized prospective cohort study of 50 men. Early detection of uric acid deposits could permit early therapeutic intervention, possibly preventing future tophi and erosions.
For the study, 50 men aged 55-85 years were consecutively recruited during routine primary care visits to the Department of Veterans Affairs (Arthritis Care Res. 2011;63:1456-62). Exclusion criteria included current or prior history of inflammatory arthritis other than gout, asymptomatic chondrocalcinosis of the knee, total knee replacement, and history of severe knee trauma. Subjects were assessed for gout using ACR clinical criteria and serum uric acid levels measurement.
Subjects underwent musculoskeletal ultrasound of the knees and first metatarsophalangeal joints. Images were read by two blinded rheumatologists, who looked for such characteristic findings as the "double contour" sign (a hyperechoic band) over the femoral articular cartilage of the knees and tophi (heterogenous material often surrounded by a small anechoic rim).
Deposits were found in 7 of 14 gout patients, 5 of 17 with asymptomatic hyperuricemia. and 1 of 19 controls. Most of those with asymptomatic hyperuricemia and deposits met none of the ACR gout criteria. Even in those who met several of the gout criteria, there was no association between the number of ACR criteria met and level of deposits.
Serum uric acid measures did not differentiate subjects with asymptomatic hyperuricemia (mean of 8.0 mg/dL) from those with gout (mean of 8.1 mg/dL). The mean value in controls was 5.5 mg/dL.
The presence of deposits was associated with higher uric acid levels in the gout patients, at 9.4 mg/ dL for the seven patients with crystal deposits and 6.9 mg/ dL for the seven without deposits. Mean serum uric acid level did not differ in asymptomatic hyperuricemia subjects with and without deposits.