A research team from the Johns Hopkins Division of Rheumatology including Alan Baer, M.D., Tracie Kurano, M.D., and Janet W. Maynard, M.D. found that a new imaging method called dual-energy computed tomography (DECT) is a promising strategy to identify affected joints in patients with gout.
Why was this study done?
DECT is a new non-invasive diagnostic tool for gout, but its sensitivity (percentage of positive results among those proven to have gout by other methods) has not been established. Currently, a diagnosis of gout is made by using a needle to sample the fluid of the inflamed joint and looking for the presences of uric acid crystals. In late stages of gout, people can develop hard deposits of uric acid crystals under the skin called tophi. Our goal was to determine how sensitive DECT was for the detection of uric acid crystal deposits in people with early (tophi absent) and late (tophi present) stages of gout.
How was this study done?
DECT was performed on 11 people with early (tophi absent) gout and 10 people with late (tophi present) gout. Each patient had several DECT images taken of the joints in their arms and legs. With this imaging technique, the uric acid crystal deposits were color-coded as green clumps on the otherwise grey-scale images. The number and location of these deposits was tallied. Sensitivity of DECT was defined as the proportion of patients with a confirmed diagnosis of gout which was correctly identified as such by the imaging technique.
Who was involved in this research?
The study team included researchers at Johns Hopkins from the Departments of Rheumatology, Radiology, and Epidemiology. The participants in the study were research volunteers seen at the Johns Hopkins University who gave their consent to participate in this study.
What were the major findings?
DECT was able to detect uric acid crystal deposits in all of the people with late stage gout and even in 64% of patients with early stage gout. Performing DECT on the legs alone was sufficient to see these deposits. This method also identified areas in which the bone was damaged as a result of the uric acid crystal deposits but could only identify 25% of the joints that were known to test positive for uric acid crystals using the traditional needle sample method.
What is the impact of this work?
Based on this study, we concluded that performing DECT on the joints in the legs has moderate sensitivity in identifying people with early gout and high sensitivity in identifying people with late. However, DECT was not as sensitive as the traditional needle biopsy in identifying all of the joints which contain uric acid crystals and cannot identify all areas where the bone has been damaged. The successful detection of these deposits by DECT relates to their size and density, so we think that this technology will continue improve and become more sensitive. This work may ultimately lead to the use of this non-invasive technique in determining the extent and severity of uric acid crystal deposits in patients with gout.
Link to original research article:
Dual-energy computed tomography has limited sensitivity for non-tophaceous gout: a comparison study with tophaceous gout. Baer AN, Kurano T, Thakur UJ, Thawait GK, Fuld MK, Maynard JW, McAdams-DeMarco M, Fishman EK, Carrino JA.BMC Musculoskelet Disord. 2016 Feb 18;17(1):91. doi: 10.1186/s12891-016-0943-9. PMID: 26891750