Development of a computed tomography method of scoring bone erosion in patients with gout: validation and clinical implications.
OBJECTIVE
To develop a method of scoring bone erosion in the feet of patients with gout using CT as an outcome measure for chronic gout studies, consistent with the components of the OMERACT filter.


METHODS
Clinical assessment, plain radiographs and CT scans of both feet were obtained from 25 patients with chronic gout. CT scans were scored for bone erosion using a semi-quantitative method based on the Rheumatoid Arthritis MRI Scoring System (RAMRIS). CT bone erosion was assessed at 22 bones in each foot (total 1100 bones) by two independent radiologists. A number of different models were assessed to determine the optimal CT scoring system for bone erosion, incorporating the frequency of involvement and inter-reader reliability for individual bones.


RESULTS
An optimal model was identified with low number of bones required for scoring (seven bones/foot), inclusion of bones over the entire foot, high reliability and ability to capture a high proportion of disease. This model included the following bones in each foot: first metatarsal (MT) head, second to fourth MT base, cuboid, middle cuneiform and distal tibia (range 0-140). Scores from this model correlated with plain radiographic damage scores (r = 0.86, P < 0.0001) and disease duration (r = 0.42, P < 0.05). Scores were higher in those with clinically apparent tophaceous disease than in those without tophi (P < 0.0001).


CONCLUSIONS
We have developed a preliminary method of assessing bone erosion in gout using conventional CT. Further testing of this method is now required, ideally in prospective studies to allow analysis of the sensitivity to change of the measure.
Department of Medicine, University of Auckland, Grafton, Auckland, New Zealand. n.dalbeth@auckland.ac.nz
Nicola
N
Dalbeth
Anthony
A
Doyle
Lucinda
L
Boyer
Keith
K
Rome
David
D
Survepalli
Alexandra
A
Sanders
Timothy
T
Sheehan
Maria
M
Lobo
Greg
G
Gamble
Fiona M
FM
McQueen
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001862:Bone Resorption / Q000000981:diagnostic imaging*; D004185:Disability Evaluation; D005260:Female; D006073:Gout / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009520:New Zealand; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000379:methods