Background/Purpose: Thrombocytopenia and hemolytic anemia (HA) are considered non-criteria clinical manifestations by the Sydney revised criteria for APS. These features can precede, follow a thrombotic event or remain as such. We aimed to evaluate the serological phenotype of patients with both conditions

Methods: We included 77 consecutive patients with primary APS according the Sydney classification criteria and/or patients with hematological features (thrombocytopenia and HA). Patients from both groups fulfilled the Sydney laboratory criteria for APS. We registered demographics, disease duration and type of manifestation. aCL (IgG and IgM), antibodies to purified human anti-β2GP-I (IgG and IgM) and IgG and IgM anti-phosphatidylserine/prothrombin (aPS/PT) antibodies were assessed by ELISA. Lupus anticoagulant (LA) was determined by LA/1 screening reactant and a confirmatory test LA/2 according to published guidelines. The reactivity of IgG antibodies to domains 1-5 of β2GP-1 genetically engineered in our laboratory were determined by immunoblotting.

Results:  Most patients were females (75.3%), mean age 45.3 ± 15 and mean disease duration 9.6 ± 6.5.The most prevalent antibody was aCL-IgM (87%) followed by anti-β2GP-l IgG (81.8%), anti-β2GP-I IgM (80%), aCL-IgG (79.2%) and LA (70%); 33% of patients were triple-positive. The prevalence of aPS/PT antibodies was 61.3% (both isotypes). Of the 62 IgG anti-β2GP-I-positive patients 31 (50%) had only thrombotic features, 14 (22.5%) hematological manifestations and 17 (27.4%) had both. They were not different in gender, age, disease duration, nor in the prevalence of aCL (both isotypes), LA, anti-β2GP-I IgM, aPS/PT–IgM or anti-D 1, 2, 4 and 5. In contrast, we found a significant difference in the prevalence of aPS/PT-IgG (70% thrombotic vs. 35.7% hematological and 87.5% both, p=0.01) and anti-domain 3 antibodies (64.5% thrombotic vs. 78.6% hematological and 33.3%, p=0.01). The logistic regression analysis of patients with both manifestations (n=17) vs. those with only one (n=45) showed that anti-D3 (OR 0.16 95% CI 0.35-0.76, p=0.02) and aPS/PT-IgG antibody (OR 11.7 95% CI 1.02-133.6, p=0.04) remained associated.

Conclusion:  We identified a serological phenotype that discriminates APS patients with both thrombotic and hematological features. This finding further supports our contention that thrombocytopenia and hemolytic anemia are part of the APS. Future studies in other cohorts are needed to validate this finding.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-%ce%b22gp-i-domain-3-and-apspt-igg-antibodies-identify-primary-aps-patients-with-both-thrombotic-and-hematological-manifestations/