THERAPEUTIC APHERESIS

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1 THERAPEUTIC APHERESIS J. Sennesael Department of Nephrology, UZ Brussel Presentation Overview Definition of therapeutic apheresis Apheresis methods Mechanism of action of therapeutic plasma exchange (TPE) Kinetics of TPE Indications for TPE TPE in renal diseases TPE in neurological diseases Complications of TPE DEFINITION OF THERAPEUTIC APHERESIS 1

2 Definition of Therapeutic Apheresis Apheresis < gr. aphaeresis: taking away, to carry Commonly performed apheresis procedures Procedure name Description Leukocytapheresis Thrombocytapheresis RBC exchange Plasmapheresis Plasma exchange LDL apheresis A procedure in which the WBCs are separated from the blood. The cells may be discarded (acute leukemia) or used for transfusion (hematopoietic progenitor cells) A therapeutic procedure in which platelets are removed and discarded from a thrombocythemic patient. A therapeutic procedure in which abnormal RBCs are removed and replaced by donated RBCs. A procedure in which plasma is separated from the blood and returned without replacing the removed volume. A procedure in which a large volume of plasma is removed, usually plasma volumes. The removed plasma is replaced with a replacement fluid. A type of plasmapheresis procedure in which the removed plasma is modified to remove LDL cholesterol and then returned to the patient. Adapted from JL Winters, Hematology 2012 APHERESIS METHODS TPE Methods Centrifugation-based TPE Centrifugal force separates cells from plasma based on their specific gravity Hematology/Bloodbank Filtration-based TPE High permeable membrane separates plasma from cellular components Nephrology 2

3 Filtration-based TPE Standard dialysis machine HDF mode, low volume High permeable membrane (MWC kd) High Permeable Membranes for TPE Gambro plasma filter PF1000 (0.15 m², ETO) Filtration 25 ml/min (1.5 l/h) Asahi plasmaflo Polyethylene (copolymer coating) OP-02 (0.2 m², gamma) Filtration ml/m OP-5W (0.50 m², gamma) Filtration ml/m (1 unit FFP 250 ml) Apheresis Methods Method Pro Con Centrifugation Peripheral blood line sufficient Can separate any blood component Lower blood flow rate Loss of platelets Greater extracorporeal volume Citrate anticoagulation Filtration No loss of platelets Less extracorporeal volume Heparin (usually) Dialysis catheter needed Substance removal depends on membrane Higher blood flow rate 3

4 MECHANISM OF ACTION OF TPE Mechanism of Action of Plasma Exchange 1. Removal of known pathogenic substances from plasma Autoantibody: Thrombotic thrombocytopenic purpura (TTP), immune thrombocytopenic purpura (ITP), myasthenia gravis (MG), Guillain-Barré syndrome (GBS), neuromyelitis optica (NMO), anti-gbm glomerulonephritis (and Goodpasture s syndrome), ANCA-associated glomerulonephritis (and Wegener s granulomatosis), antiphospholipid crisis etc. Probable autoantibody: Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), multiple sclerosis (MS), etc. Antigen-antibody complexes: Hepatitis C vasculitis, systemic lupus erythematosus, etc. Alloantibody: Transplant sensitization, transplant rejection (humoral), transfusion reactions, etc. Paraproteins: Waldenstrom s, hyperviscosity, light-chain neuropathy, light-chain glomerulopathy, myeloma cast nephropathy, etc. Non-Ig proteins: Focal segmental glomerulosclerosis (FSGS) Endogenous toxins: Hypercholesterolemia, liver failure, systemic inflammatory response syndrome (SIRS), etc. Exogenous poisons: Amanita (mushroom), drugs, etc. DM Ward, J Clin Apher 2011 Mechanism of Action of Plasma Exchange 2. Restoration of deficient factors ADAMTS 13 in TTP Complement factors in ahus 3. Immunomodulatory effects Th 1 /Th 2 modulation: shift towards TH 2 (1) Suppression of IL-2 & IFN-gamma production (2) Increased Concanavalin A-induced suppressor function (1) H Goto, Ther Apher 2001; (2) S Shariatmadar, Am J Hematol

5 KINETICS OF TPE Kinetics of Plasma Exchange DM Ward, J Clin Apher 2011 Plasma Volume Exchange Plasma Volume Exchange Percent Removed 0 100% % % % % % % 5

6 Calculating Volumes EXCHANGE VOLUME CALCULATED RELATIVE TO THE ESTIMATED PLASMA VOLUME (EPV): EPV(L) = 0.07 x weight (kg) x (1-hematoctrit) Ex: 80 kg male with Hct of 30 (0.3): EPV = 0.07 x 80 x 0.7 = 3.92 liter 1.5 plasma volumes = 3.92 x 1.5 = 5.9 liter 60 kg female with Hct of 35 (0.35): EPV = 0.07 x 60 x 0.65 = 2.73 liter 1.5 plasma volumes = 2.73 x 1.5 = 4.1 liter Number and Frequency of Treatments Underlying disease (daily in TTP, severe anti-gbm disease) Type of molecule IgM (75% intravascular): easily removed (90% in 2 sessions) IgG (45% intravascular): less easily removed (90% in 5 sessions) rebound phenomenon Desired endpoint (clinical improvement; reduction of specific substance) IN GENERAL: 5-7 sessions over 10 days, then pause and reassess M Ward, J Clin Apher 2011 Removal of Normal Plasma Components Coagulation factors Decline in F VIII, F IX, VWF (till 4 hours post PE) in F V, F VII, F X (till 24 hours post PE) Fibrinogen: 66% of pre-apheresis levels by 72 hours Inhibitors of coagulation Antithrombin Pseudocholinesterase Reduced metabolism of some drugs Prolonged neuromuscular blockade Antimicrobial Abs False negative test for infectious diseases Drugs Ceftriaxone, ceftazidime, tobramycin, cisplatin, vincristine, diltiazem, Verapamil, propoxyphene, propranolol, rituximab, IFN-alfa Adapted from JL Winters, Hematology

7 Replacement Fluids 5% Albumin or Albumin/Saline Fresh frozen plasma No viral transmission Rare reactions No depletion coagulopathy No depletion of IgG Expensive Depletion coagulopathy Depletion IgG Hypokalaemia Citrate-related problems (hypocalcemia, metabolic alcalosis) Anaphylactic reactions Viral transmission False positive testing for viral Ab INDICATIONS FOR TPE American Society for Apheresis Journal of Clinical Apheresis Volume 25- Issue Guidelines on the use of Therapeutic Apheresis in clinical practice Evidence based approach (Szczepiorkowski ZM et al.) 7

8 ASFA Guidelines Categories Redefinition of the Indications Evidence-Based Assessment of the Therapeutic Apheresis Literature Recommendations-Sub-Categories Focus on Treatment Approach to a given Clinical Condition Fact Sheets ASFA Categories Category I: Apheresis is accepted as first-line therapy (Primary of in conjunction with other modes of treatment) GRADE 1A: Strongly recommended, high quality evidence GRADE 1B: Strongly recommended, moderate quality evidence GRADE 1C: Strongly recommended, low to very low quality evidence ASFA Categories Category II: Apheresis is accepted as second-line therapy, either as standalone treatment or in conjunction with other modes of treatment GRADE 2A: Weak recommended, high quality evidence GRADE 2B: Weak recommended, moderate quality evidence GRADE 2C: Weak recommended, low to very low quality evidence 8

9 ASFA Categories Category III: Optimum role of Apheresis is not established. Decision making should be individualized Category IV: Published evidence demonstrates or suggests Apheresis to be ineffective or harmful. IRB approval is desired Indications for TPE Category I: Standard acceptable therapy Renal ANCA-associated RPGN (dialysis dependence, DAH) Anti-GBM disease (dialysis independence, DAH) Recurrent FSGS ahus (auto-ab to factor H) Ab-mediated transplant rejection Neurological Guillain-Barré syndrome Chronic idiopathic demyelinating polyneuropathy (CIDP) Myasthenia gravis Paraproteinemic polyneuropathy (IgG/IgA; IgM) Adapted from Szczepiorkowski ZM,

10 Indications for TPE Category I: Standard acceptable therapy Haematological Thrombotic thrombocytopenic purpura (TTP) Hyperviscosity in monoclonal gammopathies Autoimmune Cryoglobulinemia (severe, symptomatic) Adapted from Szczepiorkowski ZM, 2010 Indications for TPE Category II: Sufficient evidence to suggest efficacy as adjunctive therapy Renal ahus (Complement factor gene mutation) ABO incompatible kidney transplantation Desensitisation for DSA Myeloma cast nephropathy Neurological Acute disseminated encephalomyelitis Chronic focal encephalomyelitis (Rasmussen s) Lambert-Eaton myasthenic syndrome Multiple Sclerosis (acute disease, steroid resistant) Neuromyelitis Optica (Devic s syndrome) Adapted from Szczepiorkowski ZM, 2010 Indications for TPE Category II: Sufficient evidence to suggest efficacy as adjunctive therapy Haematological Pure red cell aplasia Cold agglutinin disease (life threatening) Red cell alloimmunisation in pregnancy Autoimmune Catastrophic anti-phospholipid syndrome Cryoglobulinemia (secondary to HCV) Poisoning/overdosing Mushroom poisoning Phytanic acid storage disease (Refsum s disease) Adapted from Szczepiorkowski ZM,

11 Indications for TPE Category III: Inconclusive evidence of efficacy or uncertain risk/benefit ratio Immune complex RPGN Nephrogenic systemic fibrosis Renal Neurological Multiple sclerosis (chronic progressive) Paraneoplastic neurologic syndromes Haematological Autoimmune hemolytic and aplastic anemia TMA (calcineurininhibitors, HSCT) Systemic sclerosis Autoimmune Adapted from Szczepiorkowski ZM, 2010 Indications for TPE Category III: Inconclusive evidence of efficacy or uncertain risk/benefit ratio TPE can be considered for the following occasions: 1. Standard therapies have failed 2. Disease is active or progressive 3. There is a marker to follow 4. It is agreed that it is a trial of TPE and when to stop 5. Possibility of no efficacy is understood by the patient Indications for TPE Category IV: Lack of efficacy in controlled trials Renal Goodpasture syndrome (dialysis dependent, no DAH) HUS (diarrhea associated, typical) Amyotrophic lateral sclerosis Inclusion body myositis Neurological TMA (gemcitabine, quinine) Coagulation factor inhibitors Rheumatoid arthritis (refractory) Dermato-/polymyositis Pemphigus Haematological Autoimmune Adapted from Szczepiorkowski ZM,

12 TPE IN RENAL DISEASES TPE in renal diseases Thrombotic microangiopathy Anti-glomerular basement membrane disease ANCA-associated vasculitis Hyperviscosity syndromes Cryoglobulinemia Recurrent FSGS Antibody mediated rejection Thrombotic Microangiopathy Clinical manifestations Laboratory abnormalities Fever Thrombocytopenia (No DIC) Renal failure TTP/HUS Neurologic deficits Microangiopathic hemolytic anemia schistocytes LDH haptoglobin 12

13 TPE in Thrombotic Microangiopathy Subgroup Response to TPE (%) TTP Primary Hereditary (ADAMTS 13 activity < 10%) Idiopathic or acquired Secondary Drugs (except mitomycin C) Collagen vascular disease Infection (except E. coli) Pregnancy Pancreatitis Stem cell transplant Malignancy Malignant hypertension Adapted from Clark WF, Sem Dial 2012 TPE in Thrombotic Microangiopathy Subgroup Response to TPE (%) HUS Primary: atypical HUS (ahus) Complement factor H, I or B C3 convertase, thrombomodulin Membrane co-factor protein (MCP-CD46) Secondary: diarrheal HUS (DHUS) E. coli O157: H7 (STEC) 0 Adapted from Clark WF, Sem Dial 2012 Thrombotic Microangiopathy: Adult TTP/HUS Test ADAMTS 13 Stool cultures E. coli O157: H7 Start TPE DIC Test INR, PT, D-dimer Secondary (50%) Idiopathic (50%) Stool + DHUS DIC TPE 50-70% response Collagen vascular disease, drugs, pregnancy, pancreatitis NO TPE for stem cell transplant, malignancy, mitomycin C TPE 80-90% response Supportive (volume repletion) TPE if severe acute onset/neurologic deficit Search sepsis or malignancy Adapted from Clark WF, Sem Dial

14 Thrombotic Microangiopathy: Child Bloody diarrhea Stool culture E. coli O157: H7 No diarrhea Test complement DIC Test INR, PT, D-dimer D-HUS Conservative (volume repletion) Infusion FFP (?) a-hus TPE Eculizumab DIC Search sepsis or malignancy Adapted from Clark WF, Sem Dial 2012 TPE for TTP ASFA Indication: category I Rationale: TPE is superior to FFP infusions 1,2 Replacement Fluid: FFP Interval/duration: TPE < 24 hours of presentation plasma volume (60-75 ml/kg) daily (platelets > 150x10 3 ; LDH normal) Adjunctive therapy: corticosteroids (3) Standard dose (1 mg/kg) > high dose (10 mg MPS/kg/day x3) followed by 2.5 mg/kg/day (CR 53.4% vs 23.4%, p = 0.03) (1) GA Rock; NEJM 1991 (2) M Michael, Cochrane Database Syst Rev 2009 (3) SJ Brunskill, Transf Med 2007 TTP: Response to Initial Therapy Rapid response (1-2 days) Non-focal neurologic symptoms Moderate response (3-10 days) Thrombocytopenia Parameters of hemolysis Slow response (weeks-months) Anemia Renal impairment (unpredictable, often incomplete) Treatment requires persistence and patience 14

15 TTP: Follow-up and Outcome Follow-up Duration of initial treatment is undefined Monitor blood cell count and LDH Outcome Relapse rates 29-82% Chronic renal failure ( 25%) Long-term neurologic effects (incidence?) TTP: Relaps or Refractory Patients Continue/intensify TPE Rituximab (1) Initial 375 mg/m² Weekly (x4) Splenectomy? IVIG? (1) S Jasti, J Clin Apher 2008; I de la Rubia,Transf Apher 2012 TPE for ahus ASFA indication: Category I (factor H Ab) Category II (complement factor gene mutations) Rationale: no controlled trials, expert opinion (1) Replacement fluid: FFP Interval/duration: plasma volumes daily (platelets > 150 x 10³; LDH normal) 5x/week for two weeks 3x/week for two weeks Subsequently according to evolution Uncontrolled disease: eculizumab (2) (1) C Loirat, Pediatr Nephrol 2008 (2) J Nürnberger, N Engl J Med

16 Diarrheal HUS: Treatment Supportive care FFP infusion: no significant benefit (1) TPE: benefit in adults with severe acute onset D-HUS (2) (1) G Rizzoni, J Pediatr 1988 (2) E Colic, Lancet 2011 TPE in Anti-glomerular Basement Membrane Disease ASFA indication: Serum creatinine < 500 µmol/l: category I Diffuse alveolar hemorrhage (DAH) irrespective of serum creatinine: category I Rationale for TPE: Lower post therapy serum creatinine, lower incidence of ESRD, more rapid decline of anti-gbm (1) Less severe pulmonary hemorrhage (2) Replacement fluid: albumin (FFP 2 4 units last portion of exchange if DAH or kidney biopsy) Interval/duration: TPE plasma volume daily/every other day minimum 14 days Consider continuing TPE if serum creatinine & anti-gbm level not significantly declined Adjunctive therapy: corticosteroids, cyclophosphamide (1) JB Levy, Ann Int Med 2001 (2) CO Savage, BMJ 1981 TPE in ANCA-associated Vasculitis ASFA indication: RPGN (Screat > 5.7 mg/dl); dialysis dependence (1) : category I Diffuse alveolar hemorrhage (DAH) (2) : category I Rationale for TPE: TPE is superior to IV MPS pulses in patients with severe renal involvement: renal recovery at 3 months: 69% vs 50% progression to ESRD: 24% risk reduction Replacement fluid: albumin (FFP 2-4 U last portion of exchange if DAH or kidney biopsy) Interval/duration TPE plasma volume 6-9 treatments over 2 weeks Daily initially if concomitant anti-gbm Adjunctive therapy: corticosteroids, cyclophosphamide (1) D Jayne, JASN 2007 (2) PJ Klemmer, Am J Kidney Dis

17 TPE in Hyperviscosity Syndromes ASFA indication: neurological symptoms (convulsions, coma) in monoclonal gammopathies or cryoglobulinemia: category I Rationale: Prevalence hyperviscosity symptoms with 4 and 5 cp = 67% and 75% (1) One single TPE ( plasma volume) reduces plasma viscosity by 20-30% (2) Replacement fluid: albumin (1/3)/saline (2/3) Interval/duration: Daily until acute symptoms abate (1-3 TPEs) Maintenance 1 TPE every 1-4 weeks ( clinical symptoms) Adjunctive therapy: chemotherapy (1) BD Adams, Emerg Clin N Am 2009 (2) M Ballestri, 2007 TPE for Recurrence of Primary FSGS ASFA indication: posttransplant recurrence of idiopathic FSGS: category I Rationale: TPE + high dose cyclosporine: 75% remission (1) Remission correlates with reduction of serum supar < 2000 pg/ml (2) Replacement fluid: albumin or albumin/ffp Interval/duration: Daily for 3 days + 3 times/week for 2 weeks (minimum 9) Tapering guided by degree of proteinuria Adjunctive therapy: corticosteroids, cyclosporine, rituximab(?) (1) ME Schachter, Clin Nephrol 2010 (2) C Wei, Nat Medicine 2011 TPE for Cryoglobulinemia ASFA indication: Severe organ damage (skin, kidney, neuropathy): category I Cryocrit not to be used as criterion Rationale: No RCT TPE associated with 70-80% clinical improvement (1,2) Replacement fluid: albumin or plasma Interval/duration: plasma volume exchange every 1-3/days Reevaluate after 8 procedures Weekly/monthly according to symptoms Warm room and warmed lines/replacement solutions Adjunctive therapy: according to underlying disease (1) EM Berkman, Transfusion 1980 (2) GE Russo, Transf Sci

18 TPE for Antibody Mediated Rejection (AMR) ASFA indication: antibody mediated rejection: category I Banff criteria 2001: (1) DSA; (2) allograft histology (PMN glomerular/peritubular); (3) allograft IF (C 4 d peritubular capillaries) Rationale: TPE alone (removal DSA): no benefit in RCT (1) Immunoadsorption: superior evidence (2) TPE + IVIg (inhibition of residual DSA): 50-90% reversal of AMR and improved graft survival (70-80%) (3) Replacement fluid: albumin or albumin/saline Interval/duration: no evidence based protocol Set number of TPE, usually 5 or 6, daily or every other day TPE procedures based on renal function, decrease in DSA Low dose IVIg ( g/kg) at end of each procedure Adjunctive therapy: corticosteroids, MMF, rituximab, bortezomib (1) HJ Gurland, Kidney Int Suppl 1983 (2) GA Bohmig, Am J Transplant 2007 (3) C Lefaucheur, Am J Transplant 2009 TPE IN NEUROLOGICAL DISEASES TPE in neurological diseases Guillain-Barré syndrome Chronic inflammatory demyelinating polyneuropathy (CIDP) Myasthenia gravis 18

19 TPE for Guillain-Barré Syndrome ASFA indication: severe disease impairing independent walking or requiring mechanical ventilation: category I Rationale: Anti-LOS/ganglioside antibodies 4 RCT: improvement in disability and ventilation need within 4 weeks (1-3) Replacement fluid: albumin/saline Interval/duration: plasma volume every other day 5 to 6 procedures over 2 weeks Alternative therapy: IVIG equally efficacious as TPE (4) 0.4 g/kg for 5 consecutive days (1) M.Farkkila, Neurology 1987 (2) Guilliain Barré Study group, Neurology 1985 (3) French Cooperative Group on Plasma exchange in Guillain Barré Syndrome, Ann Neurol 1987 and 1997 (4) RA Hughes, Cochrane Syst Rev 2001 TPE for Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) ASFA indication: short term treatment of CIDP: category I Rationale: Autoantibodies against proteins and glycolipids of peripheral nerves 2 RCT: improvement nerve conduction and neurologic-disability score (1-2) Replacement fluid: albumin/saline Interval/duration: plasma volume, 2 to 3 times/week until improvement (4-6 weeks) Taper as tolerated Adjunctive therapy: Corticosteroids, azathioprine, MMF, CsA IVIG equally efficacious as TPE: 0,4 g/kg once a week, x 3 0,2 g/kg once a week, x 3 (1) PJ Duyck, NEJM 1986 (2) AF Hahn, Brain 1996 (3) PJ Duyck, Ann Neurol 1994 TPE for Myasthenia Gravis ASFA indication: myasthenic crisis and pre-thymectomy: category I Rationale: Autoantibodies towards antigens in the postsynaptic membrane (AChR: 80-90%; MuSK: 10%) NO RCT Replacement fluid: albumin/saline Interval/duration: plasma volume every other day 5 tot 6 procedures over 2 weeks Adjunctive therapy: Thymectomy, acetylcholinesterase inhibitor, corticosteroids, azathioprine, MMF IVIG equally efficacious as TPE (1) : 0.4 g/kg/day on 3 to 5 consecutive days (1) P Gadjos, Ann Neurol

20 COMPLICATIONS OF TPE General Complications Catheter-related Thrombosis/hemorrhage; infection; pneumothorax Anticoagulation-related Bleeding risk Pulmonary embolism if reinfused blood not properly anticoagulated Oncotic pressure-related Hypotension if hypo-oncotic fluid replacement Pulmonary edema if serum protein much higher post TPE Elimination of drugs Drugs with high protein binding: antibiotics, anti-epileptic drugs, diltiazem, thyroxin, cyclophosphamide, azathioprine Biologicals: administer after TPE Complications when substituting albumin and/or saline Depletion coagulopathy 1 plasma exchange: coagulation factors 60%; recovery 48 hours Multiple treatments/week: pronounced depletion; recovery > 72 hours if bleeding risk (Goodpasture, postbiopsy, ): substitute 2-4 FFP Depletion of immunoglobulins 1 plasma exchange:serum Ig 60%; total body Ig stores 20% Multiple treatments/concomittant IS: risk opportunistic infections serum Ig < 500 mg/dl: IVIG mg/kg Hypokalemia 25% reduction in K + post TPE (intravasal dilution) history arrhythmia/digoxin use: add 4 mmol K + /liter albumin 5 % Albumin (Na + : 145 mmol/l; K + : <2 mmol/l; Ca 2+ : 2-3 mg/dl; Citrate: 3 mmol/l 20

21 Complications when substituting albumin and/or saline Hypocalcemia Pyrogenic reactions Anaphylactoid reactions Flushing, hypotension, abdominal cramps in patients with ACE-I 5 % Albumin (Na + : 145 mmol/l; K + : <2 mmol/l; Ca 2+ : 2-3 mg/dl; Citrate: 3 mmol/l Complications when substituting FFP Anaphylactic reactions (1.5-20%) Symptoms: fever, urticaria, pruritus, wheezing, hypotension; cardiopulmonary collapse rare interrupt procedure, antihistamines, corticosteroids, epinephrine if needed pretreatment with antihistamines and/or corticosteroids Citrate-induced hypocalcemia Citrate infused as anticoagulant or contained in FFP (17.5 mmol/l) Symptoms: perioral or distal extremity tingling; lightheadedness, nausea, vomiting; abdominal cramps, tetany, seizures; chest tightening; arrhythmia ( QT) if C a 2+ i < 35% monitor Ca 2+ i (30-60 min); prophylactic IV calcium Complications when substituting FFP Citrate-induced metabolic alcalosis Citrate HCO 3 : accumulation in renal failure if TPE and dialysis required same day: TPE first Transfusion-related lung injury (TRALI) Leucoagglutination in pulmonary circulation (HLA/leucocyte donor Ab) Symptoms: dyspnea, cyanosis (non cardiogenic pulmonary edema), hypotension 21

22 Potential Causes for Hypotension during TPE Cause Hypovolemia Inadequate volume replacement; hypooncotic fluids Anaphylaxis Reaction to plasma components Membrane bio-incompatibility Cardiac arrhythmia Citrate-induced hypocalcemia Hypokalemia (digitalis) Prevention/Treatment Bradykinin reactions Avoid ACE-I Slow removal of plasma Replace with 5% albumin, FFP, colloid (60-80%) + saline (20-40%) Minimize FFP (Pre)treatment with antihistamines, corticosteroids Minimize FFP, slow infusion IV calcium prophylaxis TRALI Minimize FFP Hemorrhage Access-related Anticoagulation, depletion coagulopathy Adequate anticoagulation Adequate FFP Pulmonary embolus Adequate anticoagulation Adapted from Kaplan A, Seminars in Dialysis, 2012 References Kaplan A. Am J Kidney Dis. 2008;52: Szczepiorkowski ZM, Winters JL. J Clin Apher. 2010;25: Seminars in Dialysis. Vol. 25, Nr. 2 (March-April),