Prevalence of misclassification and remission of antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an acquired autoimmune disorder mediated by antiphospholipid antibodies (aPLs) and accompanied by clinical symptoms in the form of arterial and/or venous thromboses or pregnancy complications. APS is a severe form of acquired thrombophilia that often requires lifelong anticoagulant treatment. As the diagnostic criteria for APS are complex, the correct diagnosis of APS is challenging. The purpose of this retrospective study was to investigate the proportion of patients diagnosed with APS that met the formal criteria for APS.

The study included patients > 18 years of age in the Capital Region and Region Zealand in Denmark with an International Classification of Diseases, Tenth Revision (ICD-10) code for APS (D68.61) in the medical record management system EPIC during the period 2016 to 2023.

Among 175 included patients, 46 (26%) did not meet the formal APS criteria. Among 53 patients less-than 50 years, APS occurred more frequently in women than in men (41 versus 12; p less-than 0.0001) but not in patients ≥ 50 years (38 versus 38). The reasons for misclassified APS were mostly incorrect interpretation of laboratory results. In ten cases, the clinical criteria were not met. In 15 patients, aPLs became negative after several months or years.

The formal APS criteria were not met in 26% of our patients. This raises the question whether better diagnostic performance can be achieved through further education, or whether the diagnosis of APS should be regarded as a specialist task.

None.

Approved by the health authorities in Denmark, project number R-23014587.