Background Diagnosis of antiphospholipid syndrome (APS) still remains a laboratory challenge due to the great diversity of antiphospholipid antibodies (aPL) and their significance regarding APS classification criteria. Standardized enzyme-linked immunosorbent assay (ELISA) for antibodies to cardiolipin (aCL) and b2-glycoprotein I (ab2GPI) has been indispensable in the diagnosis and management of APS. Multiplex detection of aPL profile seems to be a new approach for risk assessment in APS.
Objectives The comparison of the novel multi-line dot assay (MLDA) with results of the routine ELISA technique for detection of aPL in APS.
Methods We studied 36 patients (pts) with APS (5 men, 31 women, median age 34, 29-44 years). Diagnosis of APS had been established according to the 2006 international classification criteria. 15 (41,7%) APS pts met the diagnostic criteria for systemic lupus erythematosus (SLE), 28 (77,8%) had a history of arterial and/or venous thrombosis, 21 (58,3%) suffered from fetal loss. As a disease control group, 14 pts with SLE without APS (3 men, 11 women, median age 35, 27-45 years) were included. IgG/IgM antibodies to CL, b2GPI, phosphatidylserine (aPS) and phosphatidylinositol (aPI) in the pts sera were detected using a commercial available MLDA (“Medipan”, Germany). For comparison, the serum levels of IgG/IgM aCL and ab2GPI were measured by ELISA kit (“Orgentec”, Germany).
Results APS pts demonstrated a significantly higher frequency of IgG aCL, IgG and IgM ab2GPI in ELISA and IgG aCL in MLDA compared to SLE pts (p<0,05) (table 1). The agreement between both methods was good for IgG aCL, IgM aCL and fair for IgG ab2GPI, IgM ab2GPI (kappa=0,620, 0,628, 0,380 and 0,388, respectively). The frequency of discrepant results for IgG aCL, IgM aCL, IgG/ IgM ab2GPI was 16%, 18% and 30%. Multiple positivity for different aPL detected by ELISA occurred significantly more frequently in APS pts (27,8%) in contrast to SLE pts (7,1%, p<0,05). The number of multiple positive samples evaluated by MLDA in the APS group (13,9%) did not demonstrated a significant higher prevalence in comparison with the control group (7,1%, p>0,05). There was a relationship between ischemic stroke and the combination of high positive levels of IgG/IgM aCL, ab2GPI, aPS and aPI detected by MLDA in APS pts (OR 95%CI 2,45, 1,09-5,55, ρ=0,049). We didn’t find any associations between subtypes of aPL and thrombosis localization.
Conclusions MDLA present an alternative to ELISA for aPL evaluation and profiling in APS. The rate of false-positive aPL detected by MLDA in SLE pts was higher compared to ELISA. The combination of four high positive aPL measured by MLDA is a risk factor of ischemic stroke in APS.
Disclosure of Interest None Declared