Antiphospholipid Antibodies in Patients With Unexplained Articular Manifestations

Joint pain is the most common chronic pain making it one of the largest causes of disabilities in the world. Arthritis is a frequent condition that causes edema, redness, heat, loss of function and pain. It can affect one or more joints and there exist more than 100 different types.

Antiphospholipid antibodies (aPL) represent a complex and heterogeneous group of antibodies directed against anionic phospholipids or protein-phospholipid complexes. Persistent aPL have been associated with antiphospholipid syndrome (APS), which is defined by the presence of recurrent venous and/or arterial thrombosis and often pregnancy morbidity.

Immunologists at the Farhat Hached Hospital (Sousse, Tunisia) and their colleagues conducted a retrospective study including 313 patients suffering from arthritis or arthralgia without evident cause. Serum samples were collected from January 2017 to December 2019. Antinuclear antibodies (ANA), rheumatoid factors (RF) and anti-cyclic citrullinated peptides antibodies (CCP-Ab) were negative for all patients. Sera of 266 healthy blood donors (HBD) were included as normal controls.

The team detected aCL-IgG and IgM using an enzyme-linked immunosorbent assay (ELISA) kit and aCL-IgA were assessed by ELISA kit (Orgentec Diagnostika, Mainz, Germany). Highly purified cardiolipin was coated on microwells with β2GPI. Specific antibodies in the patient sample bound to antigen. microtiter plate reader and results were detected with an IRE 96microtiter plate reader (SFRI Medical Diagnostics, Saint Jean d'Illac, France). The scientists evaluated aβ2GPI-IgG and IgM by an ELISA kit (Orgentec Diagnostika) using a purified human β2GPI. aβ2GPI-IgA were assessed by ELISA kit. RF IgG, IgM and IgA were assessed using a three commercially ELISA kits, (Orgentec Diagnostika). CCP-Ab were measured by an available second-generation ELISA and ANA were detected by indirect immunofluorescence on HEp-2 cells (Euroimmun, Luebeck, Germany).

The investigators reported that out of the 313 patients, 250 were females and 63 were males. The mean age of patients was 49 ± 14 years (17–87 years). One hundred eleven patients have arthralgia and 202 have arthritis. The frequency of aCL and/or aβ2GPI (24.9%) was significantly higher in patients than in HBD (10.9%). The frequency of aβ2GPI was 23.6% in patients and 9.4% in the control group. aβ2GPI-IgA was significantly more frequent in patients than in the control group (20.4% versus 7.5%. aβ2GPI was most commonly observed than aCL in patients (23.6% versus 6.4%. IgA isotype of aβ2GPI was the most frequent in 20.4% of patients while IgG and IgM were detected in 5.4% and 2.9% respectively.

The authors concluded that they had demonstrated an elevated frequency of aβ2GPI-IgA in patients with unexplained arthralgia or arthritis. The possible pathogenic mechanism of aβ2GPI remained to be demonstrated and a prospective study is necessary to known if aβ2GPI-IgA will persist over time. The study was published on December 13, 2022 in the Journal of Clinical Laboratory Analysis.

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