The experience of treating patients with thrombotic thrombocytopenic purpura with solvent detergent plasma – response to McCarthy

Abstract

The letter from Dr McCarthy is very interesting as it describes the treatment of a large number of patients with thrombotic thrombocytopenic purpura (TTP) albeit in an apparently nonrandomised fashion. In our paper (Rock et al, 2005), we described a study that was designed to compare cryosupernatant plasma (CSP) with fresh frozen plasma (FFP) in the treatment of TTP. The study was designed to enter a total of 236 patients, but was halted due to a lack of funding after only 52 patients were entered. The study was unable to show a significant difference between CSP and FFP; however, we did not accrue a sufficient number of patients to achieve statistical significance. This data appears to be similar to that reported by Dr McCarthy in his 62 patients treated with FFP and 48 patients with CSP who had 75% and 70% survival respectively. This data are also similar to that reported by Zeigler et al (2001), who did not find a significant difference in outcome in the 24 patients they treated with CSP or FFP. We take the point that the solvent detergent plasma (SDP) provided by Vitex had a decreased total amount of von Willibrand Factor (VWF) and lacked the very high molecular weight VWF multimers normally found in plasma. However, our study (Rock et al, 2005), as referred to by Dr McCarthy,