In vitro bleeding time test can diagnose thrombotic thrombocytopenia purpura and can possibly monitor therapeutic plasma apheresis.

Thrombotic thrombocytopenia purpura (TTP) is perplexing, mainly because of its difficult diagnosis and dramatic clinical presentations, high mortality rates, and the effectiveness of empirical plasma infusions and plasma exchanges. Scientific evidence supports the hypothesis that TTP results from platelet hyperagglutination. To support this, a new in vitro bleeding time (Platelet-Stat) test was used. Eleven patients had a mean in vitro bleeding time of 7.3 ± 2.1 seconds prior to plasma exchange and eight patients had a mean of 13.6 ± 4.7 seconds after the plasma exchange procedure. Normal controls were 14 ± 2 seconds. The test was used to monitor plasma exchanges in two patients. At the time the platelet count and LDH returned to normal, the Platelet-Stat remained shortened. The two patients relapsed and required continued plasma exchanges until Platelet-Stat corrected to normal. These results suggest that plasma exchanges may be effectively monitored by Platelet-Stat rather than the traditional parameters, i.e., LDH. Therefore, the Platelet-Stat test may be a useful test to diagnose TTP and monitor therapy in this disease.