Patient selection: gout
NOTE: The 3, 6 and 12 month scores differ primarily in the multiplier for the number of attacks in the interval. The value for the 6 month score is about 2 times the value for the 12 month. The effect is to annualize the number of attacks (assuming a uniform distribution which may not be true if the person is on effective therapy).
Parameters for the 6 month interval:
(1) number of attacks during 6 months
(2) serum uric acid in mg/dL
(3) VAS for pain from 0 to 10 cm
(4) VAS for patient global assessment of disease activity (PtGA) from 0 to 10 cm
(5) tender joint count from 0 to 68
(6) swollen joint count from 0 to 66
(7) tophi number
(8) tophi dimension
GAS_3a =
= (0.17 * (attacks)) + (1.03 * SQRT(uric acid)) + (0.16 * (VAS pain)) + (0.17 * (VAS global)) + (0.07 * SQRT(tender joint)) + (0.09 * (SQRT(swollen joint)) + (0.32 * LN(1 + (tophi dimension)))
GAS_1a =
= (0.20 * (attacks)) + (0.27 * (uric acid)) + (0.31 * (VAS pain)) + (0.07 * (VAS global)) + (0.03 * (tender joint)) + (0.01 * (swollen joint)) + (0.09 * (tophi dimension))
GAS_3b =
= (0.17 * (attacks)) + (1.05 * SQRT(uric acid)) + (0.16 * (VAS pain)) + (0.17 * (VAS global)) + (0.07 * SQRT(tender joint)) + (0.08 * SQRT(swollen joint)) + (0.47 * LN(1 + (tophi number)))
GAS_1b =
= (0.20 * (attacks)) + (0.28 * (uric acid)) + (0.31 * (VAS pain)) + (0.07 * (VAS global)) + (0.03 * (tender joint)) + (0.006 * (swollen joint)) + (0.20 * (tophi number))
GAS_3c =
= (0.18 * (attacks)) + (1.01 * SQRT(uric acid)) + (0.34 * (VAS pain)) + (0.53 * LN(1 + (tophi number)))
GAS_1c =
= (0.22 * (attacks)) + (0.25 * (uric acid)) + (0.36 * (VAS global)) + (0.20 * (tophi number))
where:
• The units for tophi dimension are not reported. In Dalbeth et al (2011) tophi dimensions are for subcutaneous nodules only and either diameter in mm or the product of 2 perpendicular diameters in square mm. Presumably the dimensions for all the tophi are added together. This would be the least reproducible parameter. In addition, tophi contain some fibrous tissue which would not respond quickly to a remission.
