Significance of antiphospholipid antibodies & anti 2 glycoprotein-i antibodies in pediatric antiphospholipid syndrome

الملخص EN

Objectives: To detect the diagnostic value of serum level of anti β2 glycoprotein I (anti GPI β2) among suspected patients of antiphospholipid syndrome (APS) either in its primary form (patients with thrombotic tendency without an underlying autoimmune disorder) or in its secondary form (patients with an underlying autoimmune disorder, such as systemic lupus erythematous, SLE).

Also, to define the usefulness of this test in predicting thrombotic events in comparison to other markers of APS such as anticardiolipin aCL) and lupus anticoagulants (LA).) Methodology : Fifty eight children with suspected ant phospholipid syndrome were included in this study.

They were divided into patients with suspected primary APS (group I, n = 19) and patients with secondary APS (group II, n = 29).

According to the results of LA, patients of group I were sub classified into subgroup IA (proved primary APS, n = 10, +ve LA) and subgroup IB (undefined thrombosis, n=9, -ve LA).

Similarly, patients of group II were sub classified into subgroup IIA (APS secondary to SLE, n=9, +ve LA) and subgroup IIB (SLE without APS, n=20, -ve LA).

The results of these patients were compared to those of 30 healthy children.

Laboratory investigations were performed to all subjects including: antinuclear antibodies (ANA), anti-ds DNA, LA (using two tests), antiβ2 GPI, aCL IgG antibody in addition to routine investigations including serum creatinine, CBC, PT, PTT, ESR and routine urine analysis.

Results : highly significant differences were found regarding the results of antiβ2 GPI and LA in both groups I and II as compared to controls.

Moreover, a significant difference between groups I and II was observed for antiβ2 GPI results only being higher in group I (suspected 1ry APS).

APS subgroups (IA and IIA) also had significantly higher results of anti β2 GPI as compared to SLE patients without APS (IIB) (p < 0.01, respectively).

While, no significant differences were observed for anti β2 GPI results in subgroups IA and IIA when compared to patients of subgroup IB (p> 0.05, respectively) Frequencies of seropositive results (anti β2 GPI > 20 standard GPI units and ratio of LA > 1.36) in different groups were compared using Chi-square test.

For anti β2 GPI, it revealed highly significant differences in both groups I and II as compared to controls (p < 0.01, respectively) and a significant difference was found between groups I and II (p < 0.05).

On the other hand, LA results showed similar highly significant differences for both patients' groups compared to controls but there was no significant difference between groups I and II (p > 0.05).

The seropositivity of aCL in group IA was 80 % while it was 90% for anti β2 GPI in the same group.

The efficiency in diagnosis was higher for antiβ2 GPI in both groups 1 and 2 (90 % and 81 % respectively) while it was much lower for LA (73 % and 66 % respectively).

In group I AUC were 0.75 and 0.7 for anti β2 GPI and LA respectively with a non-significant difference between both parameters (p > 0.05).

While, in group II the performance of anti β2 GPI was better as AUC were 0.87 and 0.65 for anti β2 GPI and LA respectively with a significant difference between the AUC of both markers (p < 0.05).

Conclusion : About one half of the thrombotic events that appear to be unexplained are due to APS.

Anti β2 GPI proved itself as a sensitive and efficient test for the detection of 1ry as well as 2ry APS.

Its diagnostic value resides in being reliable for the diagnosis of APS especially when there is a strong clinical suspicion in the absence of positive aCL or LA.

In SLE patients, the presence of anti β2 GPI would be of value in the discernment of 2ry APS from other overlap symptoms of disease activity.