Components of score:
(1) Dutch functional index (Creemers 1994, in Occupational and Rehabilitation Chapter)
(2) enthesis index of Mander et al
(3) spinal pain: based on location along a 100 mm visual analogue scale (VAS)
(4) serum C reactive protein (CRP) in mg/L
(5) root joint index
Range of component scores:
(1) Dutch functional index: 0 to 4
(2) enthesis index: 0 to 90
(3) spinal pain: 0 to 100
The root joint index is based on pain in shoulders and hips on palpation and/or passive movement. Pain is graded from 0 to 3. The index is stated (page 868) to be the sum of the scores. According to the data in Table II (page 869) a score of 2 was the 90th percentile for the study population. Based on these statements, I assume that:
(1) The shoulders are graded from 0 to 3.
(2) The hips are graded from 0 to 3.
(3) The index ranges from 0 to 6.
An alternative interpretation would be to score each shoulder and hip separately, giving a maximum index of 12.
AS-DAS =
= (0.238 * (functional index)) + (1.13 * (SQRT(enthesis index))) + (0.318 * (spinal pain on VAS)) + (6.54 * LN(CRP)) + (5.245 * (SQRT(SQRT(root joint index))))
where:
• Root joints were transformed using "double square root".
Interpretation:
• minimum score: 0
• maximum score: affected by CRP level (51 mg/L was the 90th percentile for study group)
• In patients with low disease activity the AS-DAS ranged from 13.3 (10th percentile) to 40 (90th percentile) with mean 26.8 (50th percentile).
• In patients with high disease activity the AS-DAS ranged from 30.9 (10th percentile) to 60.6 (90th percentile) with mean 44.7 (50th percentile).
Limitations:
• The score needs to be validated.
