[Confirmation of antiphospholipid antibody positivity: a year's results in a cohort of 113 patients].
OBJECTIVE
To evaluate the confirmation rate of antiphospholipid antibodies (aPL), to analyze their behaviour at confirmation time, and to study the clinical value of their confirmation.


METHODS
Blood samples from 380 subjects, enrolled in this study from June 1, 2007 to May 31, 2008, were tested for anti-cardiolipin (aCL) and anti-beta2glycoprotein (abeta2GPI) antibodies using an ELISA method and for Lupus anticoagulant (LA) using a series of clotting tests. The samples of the 113 subjects resulting positive at the first testing time were assayed again to confirm antiphospholipid positivity.


RESULTS
aPL positivity was confirmed in 67 out of the 113 subjects (59.3%). Medium-high antibody levels of all, except IgM aCL, aPL/ELISA had a significantly higher confirmation rate with respect to that in subjects with low levels. The confirmation rate in the category I antibody patients (multiple positivity) was higher than that in the category II antibody subjects (single positivity). LA positivity was confirmed only when it was associated to other aPL. The cut-off of 40 GPL produced a confirmation rate equal to that resulting from a 99th percentile cut-off. Confirmation of aPL positivity made it possible for us to confirm the diagnosis of antiphospholipid syndrome (APS) in 8 out of the 113 subjects originally resulting positive (7.1%). APS clinical features were vascular thrombosis in 4 of these and pregnancy morbidity in the other 4.


CONCLUSIONS
Our data emphasize aPL positivity confirmation selectivity, and medium-high antibody levels and category I antibodies (multiple positivity) had the best confirmation rates.
Cuffaro
S
S
Cattedra e U.O.C. di Reumatologia, Università di Padova, Padova, Italia. serena.cuffaro@gmail.com
Del Ross
T
T
Tonello
M
M
Bontadi
A
A
Olivieri
S
S
Salvan
E
E
Ruffatti
A
A
Punzi
L
L
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017152:Antibodies, Antiphospholipid; D016736:Antiphospholipid Syndrome / Q000145:classification / Q000175:diagnosis; D002308:Cardiolipins / Q000097:blood*; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D016682:Lupus Coagulation Inhibitor / Q000097:blood; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D010641:Phenotype; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis; D012307:Risk Factors; D013997:Time Factors; D053482:beta 2-Glycoprotein I / Q000097:blood / Q000276:immunology
D017152:Antibodies, Antiphospholipid; D002308:Cardiolipins; D016682:Lupus Coagulation Inhibitor; D053482:beta 2-Glycoprotein I