Disease severity
| Mild | Moderate | Severe | |
| Peripheral arthritis | <5 jointsNo damage on x rayNo LOFQoL minimal impactPt. evaluation mild | ⩾5 joints (S or T)Damage on x rayIR to mild RxMod LOFMod impact on QoLPt. evaluation moderate | ⩾5 joints (S or T)Severe damage on x rayIR to mild–moderate RxSevere LOFSevere impact on QoLPt. evaluation severe |
| Skin disease | BSA<5, PASI<5, asymptomatic * | Non-response to topicals, DLQI, PASI<10† | BSA>10, DLQI>10PASI>10 |
| Spinal disease | Mild painNo loss of function | Loss of function or BASDAI>4† | Failure of response |
| Enthesitis | 1–2 sitesNo loss of function | >2 sites or loss of function | Loss of function or>2 sites and failure of response * |
| Dactylitis | Pain absent to mildNormal function | Erosive disease or functional loss | Failure of response |
*See case 1 in table 4; †see case 2 in table 4.
S, swollen; T, tender; LOF, loss of physical function; IR, inadequate response; BSA, body surface area; BASDAI, Bath Ankylosing Spondylitis Disability Activity Index; PASI, Psoriasis Activity Severity Score; QoL, quality of life; DLQI, Dermatology Life Quality Index.