Ten Features that Define Gout Classification

August 11, 2015

Diagnosing gout can be vexing. Most of the time, the diagnosis is made in the primary care setting where physicians diagnose gout by following one of six classification criteria, with the most widely used one being the 1977 American Rheumatism Association criteria.

Diagnosing gout can be vexing. Most of the time, the diagnosis is made in the primary care setting where physicians diagnose gout by following one of six classification criteria, with the most widely used one being the 1977 American Rheumatism Association (ARA) criteria. But as most physicians know, this is an imperfect process. The criteria for gout is continually studied and updated. In March, researchers reported findings from a new study that identified 10 features they say should be considered for evaluation as gout classification criteria. They also recommend the use of ultrasound and uricemia, a test to evaluate the level of uric acid in the blood, for a more accurate gout diagnosis.[[{"type":"media","view_mode":"media_crop","fid":"40313","attributes":{"alt":"","class":"media-image media-image-right","id":"media_crop_5605925424024","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"4109","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"font-size: 13.0080003738403px; line-height: 1.538em; float: right;","title":" ","typeof":"foaf:Image"}}]] The new study, published in the March 16, 2015 issue of Arthritis Care and Research, is based on data from the Study for Updated Gout Classification Criteria (SUGAR), which includes 983 patients, of which 509 (52%) were diagnosed with gout. The data was collected between January 2013 and April 2014 from 16 countries. The majority of patients were male (702), an average 58 years old and the median duration of disease since reporting the first symptoms was four years.  Led by William Taylor, PhD, of the University of Otago in New Zealand, the study’s authors highlight the following conditions as most strongly associated with gout: 

  • Joint erythema
  • At least one episode that involved difficulty walking
  • Time to maximal pain less than 24 hours
  • Resolution by two weeks of onset
  • Tophus
  • MTP1 ever involved
  • Location of currently tender joints
  • Serum urate level over 6 mg/dL (0.36 mmol/L)
  • Ultrasound double contour sign
  • Xray erosion or cyst

 

Controls included patients with:

  • Clinical diagnosis of gout (MSU crystals not observed by microscopy): 50 patients
  • CPPD: 109 patients
  • Osteoarthritis: 67 patients
  • Rheumatoid arthritis: 69 patients
  • Septic arthritis: 10 patients
  • Systemic lupus erythematosus (SLE): 5 patients
  • Spondyloarthritis: 71 patients
  • Undifferentiated arthritis: 60 patients 
  • Other: 31 patients.

 To determine if gout was present, all patients were tested for MSU crystals by arthrocentesis or tissue/tophus aspiration for polarizing microscopy. “This study represents the first phase of the effort to develop updated classification criteria, aiming to identify the pertinent items to be considered for further evaluation and to assist with decision making in that evaluation. The work in the present study concerns classification criteria rather than diagnosis,” the authors wrote. 

References:

Taylor WJ, Fransen J, et al. Study for Updated Gout Classification Criteria (SUGAR): identification of features to classify gout. Arthritis Care Research. March 16, 2015. doi: 10.1002/acr.22585.