Categorical analysis of anti–PF4/heparin antibody seroconversion events
Study and study drug . | No. patients . | Group 1, no. (%)* . | P . | Group 2, no. (%)† . | P . | Combined, no. (%) . | P . |
|---|---|---|---|---|---|---|---|
| Knee (PENTAMAKS)14 | > .999 | .07 | .13 | ||||
| Enoxaparin | 365 | 5 (1.4) | 14 (3.8) | 19 (5.2) | |||
| Fondaparinux | 388 | 5 (1.3) | 6 (1.5) | 11 (2.8) | |||
| Hip (PENTATHLON)15 | .37 | > .999 | .55 | ||||
| Enoxaparin | 984 | 1 (0.1) | 10 (1.0) | 11 (1.1) | |||
| Fondaparinux | 989 | 4 (0.4) | 11 (1.1) | 15 (1.5) |
Study and study drug . | No. patients . | Group 1, no. (%)* . | P . | Group 2, no. (%)† . | P . | Combined, no. (%) . | P . |
|---|---|---|---|---|---|---|---|
| Knee (PENTAMAKS)14 | > .999 | .07 | .13 | ||||
| Enoxaparin | 365 | 5 (1.4) | 14 (3.8) | 19 (5.2) | |||
| Fondaparinux | 388 | 5 (1.3) | 6 (1.5) | 11 (2.8) | |||
| Hip (PENTATHLON)15 | .37 | > .999 | .55 | ||||
| Enoxaparin | 984 | 1 (0.1) | 10 (1.0) | 11 (1.1) | |||
| Fondaparinux | 989 | 4 (0.4) | 11 (1.1) | 15 (1.5) |
Group 1 defined as formation of anti-PF4/heparin antibodies of IgG class from a negative baseline. Four patients in group 1 tested positive for heparin-dependent platelet-activating antibodies in the serotonin release assay (knee study: 1 in enoxaparin group, 2 in fondaparinux group; hip study: 1 in fondaparinux group).
Group 2 consisted of all non—group 1 patients who had evidence for an immune response, including the formation of IgM or IgA or both (but not IgG) anti—PF4/heparin antibodies or who had a positive test at baseline, but subsequently developed at least a 2-fold increase in reactivity in the EIA (by change in OD).