Color and duplex Doppler ultrasound may be useful in diagnosing ankylosing spondylitis and assessing response to therapy, new data suggest.
Dr. Ercüment Ünlü and colleagues presented data from a study demonstrating that color and duplex Doppler ultrasound can be used to determine the degree of sacroiliitis and spinal inflammation in patients with ankylosing spondylitis (AS).
The study included 39 consecutive patients with AS and 14 healthy, age- and gender-matched controls. Standardized ultrasound settings were applied including color Doppler gain 60–120 dB, wall filter 51–65 Hz, and pulse repetition frequency 300–850 Hz.
Patients with AS had significantly lower resistive index (RI) values in bilateral sacroiliac joints and in lumbar vertebral and thoracal vertebral paraspinal areas than healthy controls. RI is a measure of vascularity, and is expected to be lower in patients with active inflammation because of increased vascularization.
Patients with active disease, according to the Bath AS Disease Activity Index, had significantly higher mean lumbar vertebral and thoracal vertebral RI values (0.820 and 0.789, respectively) than patients with inactive disease (0.863 and 0.825, respectively). The mean RI tended to be lower around the sacroiliac joints in the active group, but the difference was not statistically significant (J. Rheumatol. 2007;34:110–6).
“The difference in spinal inflammation between active and inactive groups was prominent; however the difference in the degree of inflammation of SI [sacroiliac] joints between active and inactive groups became less significant because of the long disease duration of our AS patients,” the authors wrote. The mean disease duration was nearly 10 years.
Among patients with active disease, the ratio of men was significantly higher, as were average erythrocyte sedimentation rates, and C-reactive protein values.
A subset of 11 patients (7 men and 4 women with an average of age 38 years) was administered anti-tumor necrosis factor (TNF) therapy during the study period. Seven patients received infliximab 5 mg/kg IV initially and at week 2, 6, and 12, and four patients received etanercept 25 mg subcutaneous injections twice weekly. Doppler ultrasound measurements were performed at baseline and week 12 of therapy.
After 12 weeks of anti-TNF therapy, there were significant increases from baseline in average sacroiliac RI (0.814 to 0.884) and lumbar vertebral RI (0.821 to 0.883) values, but no significant change in thoracal vertebral RI (0.812 to 0.855), according to the authors from Trakya University Medical Facility in Edirne, Turkey, where the study was conducted.
An editorial accompanying the study called the data interesting, but said it was unfortunate that there was no comparison with MRI findings in the patients and controls (J. Rheumatol. 2007;34:5–7). MRI has been suggested as the best method of detecting sacroiliitis, but practical considerations such as cost and availability limit its use in the clinical setting.
Contrast-enhanced color Doppler ultrasonography has been shown previously to compare favorably with MRI in its ability to demonstrate sacroiliac joint inflammation. Ultrasound is also being used in the area of spondyloarthropathy to detect enthesitis and to assess its response to therapy, according to the editorial.
“The presence or absence of sacroiliitis as detected by whatever reliable, reproducible, and affordable method will continue to be a cornerstone for earlier diagnosis of AS,” the editorial stated. “Doppler ultrasonography may be a useful tool in diagnosing patients with AS and assessing response to therapy.
Further work is definitely warranted in this area.”