Related Experiment Video
Updated: Jul 8, 2026
Measuring Psoriasis Severity at Home
Published on: March 1, 2024
The occurrence of psoriatic arthritis in Denmark
O B V Pedersen1, A J Svendsen, L Ejstrup
1Department of Rheumatology, Odense University Hospital, Odense, Denmark. obpedersen@health.sdu.dk
Objective:
To apply and compare different classification criteria on a representative nationwide sample of psoriatic arthritis (PsA) twins and to estimate the prevalence and incidence of PsA.
Methods:
The study comprised three Danish nationwide twin cohorts. In 1994 37 388 Danish twin individuals and in 2002 46 418 twin individuals received a questionnaire, including questions on rheumatic diseases. Twins reporting PsA and their co-twins were classified according to the Moll and Wright and CASPAR (ClASsification criteria for Psoriatic ARthritis) criteria based on interview, clinical examination and scrutiny of medical records.
Results:
228 twin individuals reported PsA and 164 (72%) participated in clinical validation. By using the Moll and Wright and CASPAR criteria, 54 and 50 cases were diagnosed with PsA respectively. The positive predictive value of self-reported PsA was 31%. According to the Moll and Wright and CASPAR criteria the prevalence was 0.15% (95% CI: 0.13%, 0.22%) and 0.14% (95% CI: 0.11%, 0.19%) respectively. The annual incidence rate based on new self-reported cases in 2002 was 6/100 000 person-years (95% CI: 3/100 000 person-years, 11/100 000 person-years).
Conclusions:
The positive predictive value of self-reported PsA was 31%. The prevalence and incidence figures of PsA were equivalent to the previously reported occurrence in population- and hospital-based studies.
