Abstract Background and Aims Therapeutic plasmapheresis (TP) is an established therapy in different pathology according to international guidelines. There is different method of TP such as single plasma exchange (SPE) and Double plasmafiltration (DFPP) defined as non selective or semi selective method. Centrifugal (cSPE) and Filtration-membrane based (mSPE) are two different methods of SPE. These methods were already compared but few data exist about comparison of cSPE and DFPP. Objective of this ancillary study is to compare procedure time, biological variation and microcosting of patients treated with cSPE vs DFPP in a prospective single case study (Moranne O BMC neurology 2022). Method Lymphapheresis study included 5 patients with idiopathic CIPD treated with chronic TP with regular interval time and clinically stable. Vascular access was central venous catheter (CVC) for 2 patients and peripheral venous access (PVA) for 3 others. cSPE or DFPP was randomized at inclusion then patient was alternatively treated for 6 consecutive session by SPEc (Comtec, FMC KABI) or DFPP (HF 440 Infomed) sessions for a total of 30 session. The target plasma TPV) volume to be processed was 1.5 of total plasma volume and was not modified during the study. Anticoagulation was non fractionated heparin for DFPP with CVC and regional citrate for others. For each session replacement fluid was 100% human serum albumin (HSA) 4% for cSPE and 500 mls HSA for DFPP. We compare cSPE and DFPP considering each patient for (i) time session (including time preparation, time device and time before living) (ii) clinical tolerance (iii) biological tolerance (variation before and after session of Hb, Platelet, Fibrinogen) and (iv) microcosting. Quantitative values were described with median interquartile and compared with mixed model regression analysis. Results Patients have median age of 62 [56-68] years with 100% male and a BMI of 27 [23-31]. Patients were treated alternatively with 15 session of cSPE and 15 session of DFPP without difference of TPV between session (4500 mls) but significant higher blood volume process because of lower plasma fraction filtration with DFPP. Time session was not different between TP method but depend on vascular access. No difference was observed for clinical tolerance and Hemoglobin variation between methods. However a significant higher decreased of platelet and fibrinogen was observed during session with cSPE vs DFPP. The quantity of SHA infused during session was significantly higher with cSPE vs DFPP (180 g vs 20 g). Finally according to hospital's perspectives the cost is not very different between cSPE and DFPP but depends on specific material resources and pharmaceutical products of methods. Conclusion We show some differences between methods.