Abstract
IntroductionCurrently available clinical assays to detect antiphospholipid antibodies (aPL) test for IgG and IgM antibodies to cardiolipin (aCL) and β2-glycoprotein I (aβ2GPI). It has been suggested that testing for IgA aPL and for antibodies to Domain I (DI), which carries the key antigenic epitopes of β2GPI, could add value to these current tests. We performed an observational, multicenter cohort study to evaluate the utility of IgG, IgM and IgA assays to each of CL, β2GPI and DI in APS.MethodsSerum from 230 patients with APS (n = 111), SLE but not APS (n = 119), and 200 healthy controls were tested for IgG, IgM and IgA aCL, aβ2GPI and aDI activity. Patients with APS were further classified into thrombotic or obstetric APS. Logistic regression and receiver operator characteristic analyses were employed to compare results from the nine different assays.ResultsAll assays displayed good specificity for APS; IgG aCL and IgG aβ2GPI assays however, had the highest sensitivity. Testing positive for IgA aβ2GPI resulted in a higher hazard ratio for APS compared to IgM aβ2GPI. Positive IgG, IgM or IgA aDI were all associated with APS, and in subjects positive for aCL and/or aβ2GPI, the presence of aDI raised the hazard ratio for APS by 3–5 fold. IgG aCL, aβ2GPI, aDI and IgA aDI were associated with thrombotic but not obstetric complications in patients with APS.ConclusionMeasuring IgG aDI and IgA aβ2GPI and aDI may be useful in the management of patients with APS, particularly thrombotic APS.
Highlights
MethodsSerum from 230 patients with antiphospholipid syndrome (APS) (n = 111), systemic lupus erythematosus (SLE) but not APS (n = 119), and 200 healthy controls were tested for IgG, IgM and IgA antibodies to cardiolipin (aCL), aβ2GPI and aDI activity
Available clinical assays to detect antiphospholipid antibodies test for IgG and IgM antibodies to cardiolipin and β2-glycoprotein I
Positive IgG, IgM or IgA aDI were all associated with antiphospholipid syndrome (APS), and in subjects positive for antibodies to cardiolipin (aCL) and/or aβ2GPI, the presence of aDI raised the hazard
Summary
Serum from 230 patients with APS (n = 111), SLE but not APS (n = 119), and 200 healthy controls were tested for IgG, IgM and IgA aCL, aβ2GPI and aDI activity. Sera from (n = 200) healthy controls (HC) were obtained as part of the Health Survey for England (HSE) 2006 [35] and provided to us by the Health and Social Care Information Centre together with anonymised data on age, gender, ethnicity and confirmation that they had no long-term illness or history of cardiovascular disease. The clinical history of patients with APS (n = 111), summarised, was recorded in accordance with APS classification criteria [1]. Of 93 women with APS, 61 had a history of PM and 20 of those had suffered at least one thrombotic episode. Treatments at the time of sampling were recorded for patients with APS and SLE (Table 1)
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