Table 3.
25 patients in whom presenting clinical features were subsequently attributed to systemic infection and who had ADAMTS13 activity measured are compared to 62 patients with severe ADAMTS13 deficiency (activity <10%) in whom presenting clinical features were attributed to TTP.
| Clinical features and outcome | Patients with systemic infection (N=25) | Patients with ADAMTS13 <10% (N=62) | P |
|---|---|---|---|
| Demographic features | |||
| age (median, range) | 60 (26–85) | 39 (9–71) | <0.001 |
| race (% black) | 2 (8%) | 23 (37%) | 0.007 |
| gender (% women) | 11 (44%) | 51 (82%) | <0.001 |
| Clinical features | |||
| fever (%) | 15 (60%) | 13 (21%) | 0.001 |
| neurologic abnormalities (%) | |||
| major | 15 (60%) | 31 (50%) | 0.183 |
| minor | 7 (28%) | 12 (19%) | |
| none | 3 (12%) | 19 (31%) | |
| major neurologic abnormalities (%) | |||
| coma | 13 (52%) | 5 (8%) | <0.001 |
| stroke | 2 (8%) | 8 (13%) | 0.717 |
| seizure | 3 (12%) | 10 (16%) | 0.749 |
| focal deficits | 3 (12%) | 23 (37%) | 0.021 |
| Laboratory data (median, range) | |||
| hematocrit (%) | 25 (15–40) | 21 (13–30) | 0.005 |
| platelet (μL × 10–3) | 13 (2–71) | 11 (2–101) | 0.043 |
| LDH (U/L) | 1006 (256–3459) | 1378 (274–3909) | 0.087 |
| creatinine (mg/dL) | 3.7 (0.8–11.1) | 1.3 (0.7–6.5) | <0.001 |
| Pentad of clinical features (%) | 11 (44%) | 2 (3%) | <0.001 |
| Outcome | |||
| death (%) | 16 (64%) | 9 (15%) | <0.001 |
| relapse (% of survivors) | 0/9 (0%) | 18/53 (34%) | <0.001 |
Six of the 31 patients with systemic infections were excluded from this analysis because they did not have ADAMTS13 measurements. Six of all 68 consecutive patients who had ADAMTS13 activity <10% were excluded from this analysis because their clinical features were attributed to other disorders. Four of the six patients had systemic infection and are included in the infection group; in 2 additional patients the presenting clinical features were subsequently attributed to systemic malignancy and graft-vs.-host disease together with infection. Laboratory data are the most abnormal values from the day of diagnosis ± 7 days. Major neurologic abnormalities were coma, stroke, seizures, or focal neurologic signs; minor abnormalities in these 87 patients included headache, ataxia, blurred vision, and mental status changes with transient confusion.(11) The pentad of clinical features includes microangiopathic hemolytic anemia, thrombocytopenia, neurologic abnormalities (major or minor), renal function abnormalities (any serum creatinine value ≥1.5 mg/dL), and fever. For categorical data, the chisquare test was used except for the comparisons of stroke, seizure, the pentad of clinical features, and relapse. For these four clinical features the Fisher's exact test was used. Although the median values and ranges for the hematocrits and platelet counts are similar and overlapping, there was more difference in the interquartile ranges. The middle 50% of values, quartiles 1 to 3, for the patient groups for hematocrit were: Infection, 23–26%; ADAMTS13<10%, 18–24% and for platelet count: Infection 9000–19,000/μL; ADAMTS13<10%, 6000–15,000/μL