ReA develops after the age of 45.

Men are affected by AS approximately three times more often than women.

HLA-B27 is detected in about 90% of patients with ReA

Morning stiffness lasting less than 30 minutes is typical for AS.

Pain in AS decreases with physical activity but not at rest.

Rheumatoid factor is usually positive in patients with ReA.

AS may present with asymmetric arthritis predominantly in the lower extremities.

Enthesitis (heel pain) is a common manifestation of AS.

Dactylitis ("sausage digit") is the common manifistation of ReA

Uveitis is an extra-axial manifestation of AS.

Psoriasis and inflammatory bowel disease can be associated with AS.

Chronic back pain lasting 1-2 months is a feature of inflammatory back pain in AS.

Alternating pain in the buttocks is a clinical sign suggestive of AS.

The BASDAI index is used to assess disease activity in ReA.

BASDAI values above 4 indicate high disease activity.

Restriction of lumbar spine movement is a clinical criterion for AS.

Reduction of chest expansion below 2.5 cm is a radiographic criterion for AS.

MRI is more sensitive than X-ray for early detection of sacroiliitis.

NSAIDs are never used as first-line therapy in early stages of AS.

Sulfasalazine and methotrexate are types of DMARDs used in ReA

Biological therapy AS includes TNF-α inhibitors and IL-17 inhibitors.

Surgery, such as hip prosthetics, is never indicated in AS.

Secondary osteoporosis and aortic heart disease are possible complications of AS.

Functional class IV indicates full preservation of self-service and professional activity.