Can Antiphospholipid Syndrome (APS) testing be affected by pregnancy?

From the Guidelines

Pregnancy can indeed affect antiphospholipid syndrome (APS) testing results, with some women experiencing fluctuations in antiphospholipid antibody levels during pregnancy, which may lead to false-positive or false-negative test results. According to the most recent guidance from the ISTH-SSC subcommittee on lupus anticoagulant/antiphospholipid antibodies 1, APS testing is generally recommended either before pregnancy or at least 12 weeks after delivery to obtain the most accurate results. The hormonal and immunological changes that occur during pregnancy can alter the body's production of antibodies and clotting factors, potentially interfering with test interpretation, as noted in the study 1. Some key points to consider when interpreting APS testing results during pregnancy include:

• aPL positivity may fluctuate over time with or without SLE and during pregnancy, either decreasing or increasing 1
• Factor VIII increases gradually during pregnancy, which might mask the presence of LA by shortening the APTT 1
• IgG aPL levels were also significantly lower during the second and third trimesters, but among patients testing positive, IgG aCL and aβ2GPI results remained positive through pregnancy in 93% and 85% of patients, respectively 1
• Test results obtained during pregnancy or in the early post-thrombotic phase should be repeated postdelivery or at a distance from the acute thrombotic event 1. If APS testing is absolutely necessary during pregnancy, results should be interpreted cautiously by a specialist who understands these physiological changes. For definitive APS diagnosis, positive test results should be confirmed with repeat testing at least 12 weeks apart, preferably when the woman is not pregnant, as recommended by the ISTH-SSC subcommittee 1. This timing requirement helps distinguish between transient antibody elevations and true APS, which requires persistent antibody presence.

From the Research

APS Testing and Pregnancy

• APS testing can be affected by pregnancy, as pregnancy complications are a key aspect of the syndrome 2, 3, 4.
• The current standard of care for obstetric APS (OAPS) includes the use of aspirin and heparin, which has improved pregnancy outcomes in approximately 70-80% of cases 2, 5.
• However, some patients with OAPS may not meet the current classification criteria for APS, and may require alternative management plans 4.
• The presence of antiphospholipid antibodies (aPL) is a key factor in the diagnosis of APS, and testing for these antibodies is an important part of the diagnostic process 2, 3, 6.
• The clinical utility of non-criteria aPL in the diagnosis of seronegative APS is still a matter of debate, and further research is needed to improve test standardization 3.

Diagnosis and Treatment of APS in Pregnancy

• The diagnosis of APS in pregnancy is based on the presence of aPL and a history of pregnancy complications or thrombosis 2, 4, 6.
• The treatment of APS in pregnancy typically involves the use of antithrombotic therapy, such as aspirin and heparin 2, 5, 6.
• In some cases, alternative treatments such as hydroxychloroquine or statins may be considered 2, 5.
• The management of APS in pregnancy requires careful monitoring and a multidisciplinary approach to minimize the risk of complications 4.