Impact of extracorporeal photopheresis on blood and coagulation parameters

Extracorporeal photopheresis (ECP) is considered a safe treatment modality. We aimed to assess blood parameters including coagulation during ECP over time. We performed a long‐term retrospective single‐center chart review (laboratory parameters) of adult patients (n = 172) who had received ECP for any indication. We observed a significant decrease (p < 0.05) in erythrocytes, hemoglobin, and leukocytes compared to baseline levels after only one ECP procedure. This decrease persisted after 3‐, 6‐, 9‐, and 12‐months of ECP. A significant pathological decline of hemoglobin was observed in a higher proportion (26.4% and 25.2%, respectively) of patients after 6 (p = 0.0007) and 12 (p = 0.012) months of ECP. Mean corpuscular volume as well as hematocrit was significantly decreased at 3‐, 6‐, 9‐, and 12‐months of evaluation compared to baseline (p < 0.05). After 9 and 12 months of ECP we observed a further decline in lymphocyte counts (p < 0.05). Various coagulation parameters did not change significantly during ECP treatment. Even though not all alterations observed in peripheral blood of ECP patients in the present study were of clinical significance, risk for developing persistent anemia must be considered in patients undergoing ECP.

observed a significant decrease (p < 0.05) in erythrocytes, hemoglobin, and leukocytes compared to baseline levels after only one ECP procedure. This decrease persisted after 3-, 6-, 9-, and 12-months of ECP. A significant pathological decline of hemoglobin was observed in a higher proportion (26.4% and 25.2%, respectively) of patients after 6 (p = 0.0007) and 12 (p = 0.012) months of ECP. Mean corpuscular volume as well as hematocrit was significantly decreased at 3-, 6-, 9-, and 12-months of evaluation compared to baseline (p < 0.05). After 9 and 12 months of ECP we observed a further decline in lymphocyte counts (p < 0.05). Various coagulation parameters did not change significantly during ECP treatment. Even though not all alterations observed in peripheral blood of ECP patients in the present study were of clinical significance, risk for developing persistent anemia must be considered in patients undergoing ECP. (c) retransfusion of the treated buffy coat. In detail, the ECP method includes using small amounts of blood, which are treated with heparin as an anticoagulant, because the leukocytes (should be used consistently in the text…if it's better in American style with leucocytes pl use this consistently) re subsequently collected in 3-6 cycles. 1 At the end of each leukocyte collection cycle, an accumulation of blood (extracorporeal volume: 120-150 ml), with a reduced number of leukocytes, is reinfused from the ECP device into the peripheral circulation before preparing for the next cycle. When all cycles are completed, leucocytes are pretreated with 8-methoxypsoralen and then exposed to UV-A irradiation (corresponding to about 5% of all circulating cells). Thereafter, leukocytes are reinfused into the patient. 1 Edelson et al. introduced ECP in the early 80s. 2 Although ECP was initially developed for patients with cutaneous T-cell lymphoma (CTCL), it has also shown promising efficacy in a number of other severe and difficult-to-treat diseases, including graftversus-host disease (GvHD), systemic sclerosis (SSc), and atopic dermatitis (AD). [3][4][5][6][7] Even though ECP is generally well tolerated, there is a lack of studies systematically investigating laboratorybased adverse events (AEs) under ECP. [7][8][9][10][11][12] Based on these considerations, we chose a reasonable sample size of ECP patients to evaluate acute and chronic changes in peripheral blood parameters including coagulation.

| Patients
For this retrospective analysis, we included patients who were treated with ECP over the past 20 years at the Department of Dermatology, Ruhr-University of Bochum Germany. Only patients who had a history of at least 3 months of ECP treatment were included. Concomitant therapies were also evaluated. The study was conducted according to the declaration of Helsinki and followed a protocol approved by our institutional ethics review board (#4222-12).

| Extracorporeal photopheresis
ECP treatment was performed using UVAR XTS (Therakos Inc., Raritan, NJ, USA) or CELLEX (Mallinckrodt, Dublin, Ireland) instruments as recommended by updated European dermatology forum guidelines. 3,4 Most patients started ECP via peripheral venous access. During the course of treatment, a port catheter (TITAN-PORT D, Pakumed GmbH, Germany) was implanted in some patients. In most cases, ECP was performed on two consecutive days every 4 weeks, except for patients with CTCL and AD receiving two consecutive ECP procedures every 2 weeks over a 6-12-week period. 3,4 Heparin was used as an anticoagulant.

| Statistics
Data analysis was performed using the statistical package MedCalc Software version 19.6.1 (MedCalc, Ostend, Belgium). Distribution of data was assessed by the D'Agostino-Pearson test. For non-normally distributed data, the median and range were calculated. Data were analyzed using the Friedman-ANOVA, Spearman correlation procedure, and Chi 2 -test. p-values less than 0.05 were considered significant.

| RESULTS
All in all, 172 patients were included (103 males, 69 females; median [range] age: 53 years ). Among these were patients with AD  In 56% of patients studied, IDA could be detected over time. 9 In the present study, the number of patients with a pathological decrease in hemoglobin levels roughly doubled compared to baseline levels with a total incidence of 25% over time. This relatively low incidence compared to the studies discussed above may be explained by differences in the patient population. Specifically, our patient collective included a high percentage of patients with AD who are generally not prone to develop anemia. As expected, a decrease in hemoglobin levels, MCV, and hematocrit was also accompanied by a decrease of erythrocyte count. Erythrocyte loss may be explained by blood clotting that may occur during the leukapheresis procedure and technical issues during Anticoagulation through heparins or citrate is essential for maintaining the extracorporeal blood flow on the apheresis circuit. 17

ACKNOWLEDGMENTS
We would like to thank all colleagues at our ECP unit who have been treating our patients with great care and devotion over a period of 25 years. This work is part of the doctoral thesis of Maria Chatzipantazi.

CONFLICT OF INTEREST
Thilo Gambichler has received speakers and/or advisory board honoraria from BMS, Sanofi-Genzyme, MSD, Novartis Pharma, Roche, Abbvie, Almirall, Janssen, Lilly, Pfizer, Pierre Fabre, Merck-Serono, outside the submitted work. Laura Susok has received speakers and/or advisory board honoraria from BMS, Sun-Pharma, MSD, and Novartis. All other authors have no conflict of interest to declare.

AUTHOR CONTRIBUTIONS
Thilo Gambichler and Laura Susok contributed to the study conception and design. Material preparation, data collection, analysis, and interpretation were predominantly performed by Thilo Gambichler, Maria Chatzipantazi, Rene Stranzenbach, Alicia Feldkamp, and Laura Susok. The first draft of the manuscript was written by Thilo Gambichler. All authors read the manuscript, revised it critically, and approved the final manuscript.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding author upon reasonable request.