Impact of centrifugal therapeutic plasma exchange on platelet counts in patients with neurological autoimmune diseases

[Objective] To assess the effect of a centrifugal haemocyte separator on platelet counts in patients with neurological immune-mediated disorders during/after therapeutic plasma exchange (TPE). [Methods] This study included 189 patients (108 females and 81 males) who were treated in the department of neurology at Huashan Hospital, Fudan University, from March 2021 to March 2022. A total of 820 TPE treatments were carried out. Each patient received 2 to 5 TPEs, with each TPE amounting to the patient's plasma volume. The peripheral blood cell counts of the patients were evaluated before TPE and after 2 to 5 TPEs. [Results] The duration of a single TPE in this study was 94(84,107) minutes, and the actual volume of a single TPE replacement was 2 456(2 142, 2 785) mL. The number of patients who underwent TPE for 2, 3, 4, and 5 sessions was 17, 28, 18, and 126, respectively. The platelet (PLT) counts of the patients before and after the TPE were 195×109/L (range:150 to 245) and 220×109/L (range:170 to 270), respectively (P<0.05). Consequently, the overall PLT counts exhibited a significant decrease from baseline following TPE, yet the PLT counts remained within the normal range after TPE. Spearman's correlation analysis indicated that platelet loss did not correlate with the duration of TPE (ρ=0.037), the age of the patient (ρ=0.015), or the volume of the single replacement fluid (ρ=0.034), P>0.05, weakly correlated with the number of TPE sessions (ρ=0.017), and moderately correlated with the PLT counts before TPEs (ρ=0.446). [Conclusion] The TPE procedure exhibited a measurable impact on the patients' platelet levels, but the platelet counts remained within the normal range, therefore did not interfere with the patients' subsequent treatment protocols. The decrease in platelet level was correlated with the baseline platelet level before treatment and the number of TPE sessions.