Seasonal distribution of antiphospholipid antibodies.

BACKGROUND AND PURPOSE: The purpose of this study was to determine if there was a seasonal variation in antiphospholipid antibody (aPL) titers and whether this variation differed between stroke cases and control subjects. METHODS: IgG and IgM anticardiolipin and antiphosphatidyl serine antibody titers were obtained on serum samples from 884 stroke patients and 1024 control subjects over a 7-year period. Temporal distributions by month of blood draw were evaluated. RESULTS: Marked seasonal differences in the proportion of positive titers were found for control subjects, but no seasonal variability among patients was noted. In control subjects, positive titers occurred less frequently in the summer months, mirroring the seasonal trends seen in respiratory track infections and rheumatic fever. CONCLUSIONS: Our data suggest some aPL antibodies arise from different origins in patients and control subjects. The seasonality observed in the apparently normal population may be related to antibodies of infectious origin and is consistent with the reported lack of association with thrombosis of infection-related antibodies.

Performance of automated slidemakers and stainers in a working laboratory environment - routine operation and quality control.

The automated slidemaker/stainers of the four Beckman Coulter LH755 hematology systems in our laboratory are operated as analyzers, with similar requirements for setup, maintenance and quality control. A study was performed to confirm that these slide maker/stainers in routine use produce peripheral blood films that are completely satisfactory for microscopy and without cells, particularly abnormal cells, being pulled to the edges or sides of the film outside the usual working area. One hundred and thirty-nine automated blood films that had been produced during routine operation were compared with well-prepared manual films from the same patients. None of the films was unacceptable for microscopy. The distributions of normal white cell types within the counting areas of automated films compared with manual films, for all 139 samples for WBC from 1.0 to 352.8 x 10(9)/l; for blasts and promyelocytes in the 65 samples in which they occurred and for nucleated red blood cells in the 58 samples in which they occurred all fell within the expected limits of 200 cell differential counts of CLSI H20-A. Red cell morphology and the occurrence of WBC clumps, platelet clumps and smudge cells were comparable between the automated and manual films of all samples. We conclude that automated slidemaker/stainers, as typified by those of the Beckman Coulter LH755 system, are capable of producing blood films comparable with well-prepared manual films in routine laboratory use; and that the maintenance and quality control procedures used in our laboratory ensure consistent high quality performance from these systems.

Antiphospholipid antibodies accelerate plasma coagulation by inhibiting annexin-V binding to phospholipids: a "lupus procoagulant" phenomenon.

The antiphospholipid syndrome is a thrombophilic condition marked by antibodies that recognize anionic phospholipid-protein cofactor complexes. We recently reported that exposure to IgG fractions from antiphospholipid patients reduces the level of annexin-V, a phospholipid-binding anticoagulant protein, on cultured trophoblasts and endothelial cells and accelerates coagulation of plasma exposed to these cells. Therefore, we asked whether antiphospholipid antibodies might directly reduce annexin-V binding to noncellular phospholipid substrates. Using ellipsometry, we found that antiphospholipid IgGs reduce the quantity of annexin-V bound to phospholipid bilayers; this reduction is dependent on the presence of beta2-glycoprotein I. Also, exposure to plasmas containing antiphospholipid antibodies reduces annexin-V binding to phosphatidyl serine-coated microtiter plates, frozen thawed washed platelets, activated partial thromboplastin time (aPTT) reagent and prothrombin time reagent and reduces the anticoagulant effect of the protein. These studies show that antiphospholipid antibodies interfere with the binding of annexin-V to anionic phospholipid and with its anticoagulant activity. This acceleration of coagulation, due to reduced binding of annexin V, stands in marked contrast to the "lupus anticoagulant effect" previously described in these patients. These results are the first direct demonstration of the displacement of annexin-V and the consequent acceleration of coagulation on noncellular phospholipid surfaces by antiphospholipid antibodies.