title: Anticardiolipin antibodies: clinical consequences of "low titers".
abstract: OBJECTIVE
  To clarify the implications of low levels of immunoglobulin (Ig)-G or IgM anticardiolipin antibodies.
  
  
  METHODS
  Women who underwent clinically indicated testing for antiphospholipid antibodies were divided into four groups based on results: 1) high-positive (lupus anticoagulant or more than 19 IgG binding units of anticardiolipin antibodies; N = 131), 2) low-positive IgG (fewer than 20 IgG binding units; N 93), 3) IgM only (more than nine IgM binding units; N 97), and 4) negative (N = 153). The development of antiphospholipid antibody-related disorders was assessed for the time interval from initial antibody testing to patient interview. The median study interval for each group was at least 4 years. Forty-five percent of women had repeat testing at the time of interview.
  
  
  RESULTS
  Women in the high-positive group were more likely to develop at least one new medical complication than those in the low-positive IgG (odds ratio [OR] 4.49, 95% confidence interval [CI] 2.01-10.03), IgM only (OR 6.00, 95% CI 2.65-13.59), and negative (OR 9.11, 95% CI 3.92-21.2) groups. In contrast, the low-positive IgG, IgM only, and negative groups had similar risks for the development of new disorders. Twelve of 129 (9.3%) women in the low-positive IgG, IgM only, or negative groups had lupus anticoagulant or more than 19 IgG binding units on retesting. Half of these women developed at least one new disorder.
  
  
  CONCLUSIONS
  Women with IgM or low levels of IgG anticardiolipin antibodies comprise distinct populations from those with lupus anticoagulant or moderate to high levels of anticardiolipin antibodies. These women are not at risk for antiphospholipid antibody-related disorders beyond the risk conferred by their medical histories. However, repeat testing is warranted with new or recurrent clinical symptoms.
authors.affiliation: Department of Obstetrics and Gynecology, University of Utah School of Medicine, Salt Lake City, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Silver
authors.forename: T F
authors.initials: TF
authors.lastname: Porter
authors.forename: I
authors.initials: I
authors.lastname: van Leeuween
authors.forename: G
authors.initials: G
authors.lastname: Jeng
authors.forename: J R
authors.initials: JR
authors.lastname: Scott
authors.forename: D W
authors.initials: DW
authors.lastname: Branch
mesh_terms: D000328:Adult; D017153:Antibodies, Anticardiolipin / Q000097:blood*; D016736:Antiphospholipid Syndrome / Q000150:complications / Q000276:immunology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D016682:Lupus Coagulation Inhibitor / Q000097:blood; D011247:Pregnancy; D011248:Pregnancy Complications / Q000209:etiology
chemical_list: D017153:Antibodies, Anticardiolipin; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D016682:Lupus Coagulation Inhibitor