Table 2. Descriptive statistics of ASDAS components, ASDAS and ASDAS disease activity states in complete case data.
| Baseline | 6 months | 12 months | |
| Number of registrations, n | 6753 | 6318 | 4389 |
| Patient global assessment, mean (SD) | 6.7 (2.4) | 3.2 (2.6) | 2.7 (2.4) |
| BASDAI Q2, mean (SD) | 6.9 (2.4) | 3.2 (2.7) | 2.9 (2.5) |
| BASDAI Q3, mean (SD) | 4.7 (3.2) | 2.2 (2.6) | 1.9 (2.4) |
| BASDAI Q6, mean (SD) | 6.1 (3.0) | 2.6 (2.6) | 2.2 (2.4) |
| CRP, mean (SD) | 18.2 (25.6) | 5.1 (9.5) | 5.2 (9.9) |
| ASDAS, mean (SD) | 3.7 (1.1) | 2.0 (1.0) | 1.8 (0.9) |
| ASDAS<2.1, n (%) | 545 (8.1%) | 3923 (62.1%) | 2994 (68.2%) |
Complete case data are defined as the pooled registrations with complete data for ASDAS at baseline, 6 or 12 months after treatment.
ASDAS consists of four questions reported by the patient (on back pain, peripheral pain/swelling, duration of morning stiffness and global disease activity) and CRP.5 BASDAI questions are used to evaluate back pain (BASDAI Q2), peripheral pain/swelling (BASDAI Q3) and duration of morning stiffness (BASDAI Q6) in ASDAS formula, while the use of a CRP of 2 mg/L if CRP<2 mg/L is recommended,49 ie, ASDAS=0.121×(BASDAI Q2)+0.110×PGA+0.073×(BASDAI Q3)+0.058×(BASDAI Q6)+0.579×ln(max(CRP,2)+1).
Phrasing of the individual BASDAI questions used in ASDAS formula:
BASDAI Q2. How would you describe the overall level of inflammatory neck, back or hip pain you have had?
BASDAI Q3. How would you describe the overall level of pain/swelling in joints other than neck, back or hips you have had?
BASDAI Q6. How long does your morning stiffness last from the time you wake up?
ASDASAxial Spondyloarthritis Disease Activity ScoreBASDAIBath Ankylosing Spondylitis Disease Activity IndexBASDAI Q2BASDAI question 2BASDAI Q3BASDAI question 3BASDAI Q6BASDAI question 6CRPC-reactive proteinPGAPatient Global Assessment