Biological and clinical features in preclinical and (very) early spondyloarthritis

Spondylarthropathy (SpA ) is second most common form of chronic inflammatory
arthritis. It affects young adults between 20-40 years of age. This disease can
lead to impairement in daily activity, due to inflammation of the peripheral
and axial joints, ankylosis and joint erosions. Due to insidious onset, early
symptoms are often missed, leading to a diagnostic delay of more than 10 years.
Thanks to the early referral strategies and the introduction of MRI, this delay
is reduced to 5-6 years, however, this is still far too long.
Therefore we would like to apply and integrate all knowledge of this disease on
early SpA, to healthy individuals at risk of developing SpA. Therefore we chose
to look into first degree relatives (FDRs) since we know that the recurrence
risk is much higher than non relatives. An HLA-B27 positive FDR has a
recurrence risk of 30-40%.

1) To detect undiagnosed clinical SpA in First degree relatives (FDRs)
2) To identify biomarker alterations in subclinical SpA
3) To investigate prospectively which individuals will develop clinical SpA
over time and correlate that to the baseline clinical and
biological features

-Observational prospective cohort of 5 years, where FDRs are followed up yearly
for 5 years.

- A total of 6 study visits are planned in five years. An seperate MRI date will be planned if we are not able to perform MRI on same date as first appointment. If participants have complaints (back pain, arthritis), an extra unscheduled visit will be planned and maybe another MRI will take place in case of back pain >3 months. - A questionnaire will be held during each visit, with a duration of 15 minutes, containing questions about complaints and impairments. - A total of 6x blood will be drawn (and also extra time during an unscheduled visit, if applicable). The total amount of blood drawn at first visit will be around 48 mL (9 tubes) and for the other visits 24 mL per visit (5 tubes). - Three times during the study, X-rays will be made of Barsony, lumbar and cervical spine. The total radiation amount is 4.6 mSv. In case of an unscheduled visit (new back pain >3 months) extra series will be made, which lead to a total radiation amount of 6.9 mSv.