New Diagnostic Procedure

Until now, the usual method for diagnosing gout has been to remove fluid from the joint and analyze it for monosodiumurate crystals (uric acid). Computed tomography or CT hasn't been of much use as a diagnostic procedure for the disease because it cannot identify uric acid deposits. But a new kind of computed tomography called dual-energy computed tomography or DECT may just eliminate the need for the standard but painful method of gout diagnosis.

A study underway at Canada's Vancouver General Hospital suggests that DECT can find gout fast without being invasive. So far, DECT has been shown to have a high sensitivity for finding uric acid deposits. DECT employs two X-ray tubes that produce different energies at the same time.

The various available imaging technologies can help doctors locate gout lesions but none of them, including X-ray, MRI, ultrasound, or CT have proven sufficient to support a confirmed diagnosis of gout. Doctors rely on the traditional diagnostic procedure which involves needle aspiration of the inflamed joint to remove fluid which is then examined for the presence of uric acid. The procedure is painful, and can be difficult where inflammation is severe. Even when a puncture is successful, the amount of fluid obtained may not be enough to confirm the diagnosis. Because of these difficulties, the medical community has long desired a workable noninvasive diagnostic technique for gout.

Dual-energy Algorithm

Dr, Savvas Nicolaou, the Director of Emergency Radiology at Vancouver General Hospital and Associate Professor at the University of British Columbia in Vancouver in conjunction with Siemens, the only manufacturer of the DECT equipment, has developed, along with Nicolaou's rheumatology and radiology colleagues, a dual-energy algorithm for the purpose of identifying uric acid deposits in gout patients.

The Canadian research team used the SOMATOM Definition from Siemens for this study. The SOMATOM's commercial counterpart is called the Syngo DE Gout.

Gout Tophi

After developing the algorithm, Nicolaou and his team went on to investigate whether DECT is reliable in detecting gout tophi and if, in fact, DECT is superior to the traditional method diagnosis. The scientists also hoped to discover whether DECT was capable of ruling on a borderline case where the levels of uric acid are just below the levels which would confirm a diagnosis of gout.

Twenty participants were recruited for this study. Half had been diagnosed by the usual means of joint puncture and aspiration of fluid, and half did not have clinical gout. Participants underwent a rheumatological examination and DECT. DECT images were executed by two separate, independent radiologists.

Promising Technique

Those ten participants already diagnosed with gout had positive findings with DECT, as well. Those in the control group all had negative results with DECT imaging. Nicolaou comments that, "DECT is a promising new technique that can in a reliable, noninvasive fashion confirm the presence of gout tophi subclinically, provide information on the patient's disease burden and enable differentiation from other diseases. This technique may be used for monitoring treatment success and can be used to resolve unclear cases."