Preservation of factor VIII activity in plasma by different freezing techniques, as determined with a chromogenic microtray assay

Progressive Prothrombotic State in Women With Advancing HIV Disease

BACKGROUND

HIV-infected patients are at increased risk for venous thrombotic events (VTEs). We sought to determine if advancing stages of HIV were associated with coagulation abnormalities that could predispose to VTE.

METHODS

Functional protein S, factor VIII activity, and lupus anticoagulant were assayed in 144 participants of the Women's Interagency HIV Study. Women with conditions associated with VTE (cancer, pregnancy, hormone use, acute infection, cancer, and autoimmune disease) were excluded. Subjects included 34 women with history of clinical AIDS, 11 with immunologic AIDS (CD4 count, <200 cells/dL), 49 with asymptomatic HIV, and 50 HIV-negative comparators.

RESULTS

We found progressive decreases in protein S, when comparing HIV-negative women (median, 76%) to women with asymptomatic HIV (median, 67%), immunologic AIDS (median, 62%), or clinical AIDS (median, 46%; P < 0.0001). Similarly, advancing HIV was associated with stepwise increases in factor VIII, from a median of 116% in HIV-negative women to 149% in those with asymptomatic HIV, 196% in those with immunologic AIDS, and 211% in those with clinical AIDS (P < 0.0001). No subject had lupus anticoagulant.

CONCLUSIONS

Advancing HIV is associated with progressive abnormalities of protein S and factor VIII; both of which are associated with increased risk for VTE, thus providing a biologic mechanism for the increased prevalence of VTE in HIV.

Stability of canine factor VIII and von Willebrand factor antigen concentration in the frozen state

The stability of factor VIII and von Willebrand factor antigen concentration in the frozen state was assessed. Citrated plasma was obtained from 10 healthy, mixed breed dogs and separated into 300 microliters aliquots. One aliquot was assayed immediately and the others were frozen at either -20 degrees C or -70 degrees C. The activity of factor VIII and the concentration of von Willebrand factor antigen were measured after one week and one, two, three, four, five, six, eight and 10 months of storage. There were minor changes in both variables, particularly after four months, resulting in a decrease in the activity of factor VIII and an increase in the concentration of von Willebrand factor antigen. The changes were more pronounced at -20 degrees C. However, both factors remained relatively stable for the whole period.