New criteria for diagnosing and classifying gout are helping not only researchers but also those working at the bedside.
The joint American College of Rheumatology–European League Against Rheumatism 2015 gout classification criteria were created by a team of 19 physicians and 1 epidemiologist/biostatistician, with the team being drawn from the United States, Mexico, Europe, and New Zealand. The criteria were designed to provide a standardized and validated way to identify people with the condition by those seeking to enroll patients with gout in clinical studies, explained lead author Tuhina Neogi, MD, PhD, FRCPC.
“The classification criteria are not intended to capture all possible presentations of the condition and as such…are not intended to [be used diagnostically] since there are a whole host of factors that a physician needs to consider when making a diagnosis,” Dr Neogi, Associate Professor of Medicine and Epidemiology, Boston University School of Medicine, told Value-Based Care in Rheumatology.
However, a rheumatologist who was not involved in the development of the criteria respectfully differed.
“Rheumatology is still an art, since it is reliant on clinical judgment. And for trainees and early-career rheumatologists, classification criteria serve as an important framework upon which to build a clinical repertoire,” said Shikha Mittoo, MD, MHS, Staff Rheumatologist and Co-Research Director, Interstitial Lung Disease Program, University Health Network/Mount Sinai Hospital, and Assistant Professor, University of Toronto. “[The criteria] also are essential because other conditions—for example rheumatoid arthritis or psoriatic arthritis—can present as gout, and thus they help ensure the right patients are enrolled for the right studies, with no misclassification. The implication of this is not only for diagnosis and management decisions, but also, over time, drug costs.”
The meticulously developed criteria can be used with or without determining whether monosodium urate monohydrate (MSU) crystals are present. This is because while MSU positivity is the gold standard for gout diagnosis, not all clinics that refer patients for possible study inclusion have the capacity for synovial fluid or tophus aspiration to detect MSU crystals. The criteria also can be used in the absence of data from newer imaging modalities, because some referring clinics do not have access to these.
The first step in the criteria is that individuals have had at least 1 episode of bursal or peripheral joint swelling, pain, or tenderness. The other elements of the system include clinical criteria such as pattern of joint/bursa involvement, and characteristics and time course of symptomatic episodes. In addition, they include measurement of serum urate and assessment of MSU negativity or positivity. Imaging criteria are also included—the presence of a double-contour sign on ultrasound, or of urate on dual-energy computed tomography, or of radiographic gout- related joint erosion.
Furthermore, a unique aspect of the criteria is that 2 categories can produce negative scores—if the synovial fluid is MSU negative, 2 points are subtracted from the total score, and if the serum urate level is <4 g/dL (<0.24 mmol/L), 4 points are taken away.
The sensitivity of the full set of criteria is 92% and the specificity 89%. Without MSU assessment or imaging results, the criteria’s sensitivity is 85% and specificity 78%.
Neogi T, Jansen TL, Dalbeth N, et al. 2015 gout classification criteria: an American College of Rheumatology/European League Against Rheumatism Collaborative Initiative. Arthritis Rheumatol. 2015;67:2557-2568.