Clinical laboratory testing for the antiphospholipid syndrome

Area of Science:

• Immunology
• Clinical Chemistry
• Rheumatology

Background:

• The anticardiolipin (aCL) test, developed in 1983, is a cornerstone in Antiphospholipid Syndrome (APS) diagnosis.
• While established, the aCL test has limitations leading to diagnostic uncertainty and misinterpretation.
• Newer, more specific assays like beta2GPI ELISA have emerged, offering improved diagnostic potential.

Purpose of the Study:

• To evaluate the continued utility of the aCL test in APS diagnosis.
• To assess the role of newer diagnostic markers alongside traditional tests.
• To provide recommendations for optimizing APS diagnosis through a combination of assays.

Main Methods:

• Review of existing diagnostic criteria and assay methodologies for APS.
• Comparison of sensitivity and specificity between aCL ELISA, LA tests, and newer assays (beta2GPI ELISA, APhL ELISA).
• Analysis of clinical data associated with specific antibody profiles, including IgA aCL and anti-beta2GPI.

Main Results:

• The aCL test, despite limitations, is highly sensitive and essential for capturing most APS patients when used with the LA test.
• Newer tests like beta2GPI ELISA offer greater specificity.
• Isolated IgA aCL or anti-beta2GPI positivity is rare but clinically significant, necessitating their inclusion in diagnostic protocols.

Conclusions:

• The aCL test should remain part of the diagnostic criteria for APS.
• Combining aCL and LA tests with newer assays, including IgA aCL and various anti-beta2GPI isotypes (IgG, IgM, IgA), enhances diagnostic accuracy and reliability for APS.
• Validated ELISA kits and semiquantitative reporting improve the reproducibility and clinical utility of the aCL assay.