A clinical study of anti-NDP in the sera of patients in a large repetitive hemodialysis program

Anti‐N‐Like and Anti‐Form Red Cell Antibodies in Chronic Hemodialysis Patients

Allogeneic red blood cell (RBC) transfusions and the use of reusable dialyzers sterilized with formaldehyde can lead to RBC alloimmunization in chronic hemodialysis patients. The formed RBC alloantibodies have been implicated in immediate kidney allograft failure and decreased RBC survival observed in these patients. Using indirect antiglobulin test, direct antiglobulin test (DAT), and direct Polibrene test (DPT), we detected an RBC alloimmunization rate of 17.2% (11/64) in transfused hemodialysis patients, and found the presence of anti-N-like and anti-Form antibodies in 5 (5.7%) and 53 (60.9%) individuals, respectively. The sensitivity rate of the DPT was significantly higher than that of the DAT in detecting anti-Form, but the DAT showed a higher specificity rate compared with the DPT. We conclude that patients treated with reusable dialyzers sterilized with formaldehyde may develop specific RBC alloantibodies that could increase the potential risk of hemolysis, decrease survival of RBCs, and increase the need of blood supply.

Resistance to erythropoietin: immunohemolytic anemia induced by residual formaldehyde in dialyzers

Because of inadequate renal synthesis of erythropoietin, the anemia associated with chronic renal failure has been treated successfully in most patients on hemodialysis with recombinant human erythropoietin. Hemolysis due to anti-Nform antibody in dialysis patients with the reused dialyzer may be one of the factors that cause refractoriness to erythropoietin therapy. Patients who do not respond to erythropoietin administration should be screened for anti-Nform antibody.

Formaldehyde kinetics and bacteriology in dialyzers

The kinetics of formaldehyde washout in new and reused dialyzers with 2% (w/v) and 4% formaldehyde solution was studied. Using a standard method of rinsing, the concentration of formaldehyde decreases exponentially, but the rate of decrease and the steady-state level depends on the type of dialyzer. The residual quantity of formaldehyde using a 4% solution is more than twice that seen with a 2% solution in similar dialyzers. Bacteriological tests on water-adapted, formaldehyde-resistant organisms indicate that a significant proportion of these organisms can survive a 4-hr incubation with 4% formaldehyde at 20 degrees C. However, increasing the temperature of incubation to 40 degrees C or the addition of ethanol up to 8% (v/v) improved the bacteriological efficacy of formaldehyde. Under these conditions, a 1% formaldehyde solution allows eradication of all organisms tested. Similar results were observed in multiple-use dialyzers inoculated with the same organisms. There was no effect of incubation at 40 degrees C on the in vitro clearance determinations of new and reused dialyzers.

An immunochemical study on anti-N antibodies from dialysis patients

The specificity of anti-N antibodies from dialysis patients was investigated by hemagglutination in-hibition tests, using various fractionation, fragmentation and modification products of human erythrocytic membrane sialoglycoproteins. The antibodies were found to react with the N and "N' antigens on the MN and Ss glycoprotein, respectively. The NH2-terminal leucine and the side chain(s) of sialic acid(s) in oligosaccharide(s) linked to the second, third and/or fourth position(s) of the glycoproteins represent parts of the binding site for the anti-N antibodies. Formaldehyde reacts with the amino group of the NH2-terminal leucine, presumably leading to the formation of the hydroxy-methylene-derivative. These modified N antigens represent the structures triggering the formation of anti-N antibodies in dialysis patients, which cross-react with the native N receptors.

Relationship between formaldehyde-related antibodies and cross-reacting anti-N-like antibodies in patients undergoing chronic haemodialysis

An attempt was made to determine the sequence of events leading to the production of two distinct antibodies in patients with chronic renal failure who regularly undergo haemodialysis with formaldehyde-resterilizable dialysis units by Multipoint (UK) or Cordis (USA). A distinct pattern emerged-namely, the production of anti-formaldehyde red cells started about six months after the beginning of haemodialysis treatment. Only when the titre of these antibodies reached 64 or 128 another, apparently cross-reacting, antibody appeared which reacted like an anti-N antibody. A strong direct antiglobulin reaction was found to be positive for formalin-treated red cells after five minutes' contact with specific antibody, indicating a high affinity of the antibody fo the formalin-altered red cell.

Haemolysis due to formaldehyde-induced anti-N-like antibodies in haemodialysis patients

During reuse of formaldehyde sterilized Kiil-dialysers, red cell survival, measured by means of 51Cr t/2, was significantly reduced (p less than 0.001) in 16 patients with anti-N-like positive sera, when compared with 19 antibody negative control patients (mean +/- SD: 16.5 +/- 2.7 versus 22.4 +/- 3.1 days.) In antibody negative patients (n = 10) replacement of formaldehyde sterilized dialysers by ethylene-oxide sterilized disposable dialysers resulted in a significant increase (p less than 0.002) of 51Cr t/2 (Mean +/- SD, days: Kiildialyser 16.3 +/- 1.9; disposable dialyser 20.3 +/- 3.5). This improvement took place, although antibody titres persisted during the 51Cr-measurements and declined thereafter only slowly. In antibody negative patients (n = 6) red cell survival did not increase, when formaldehyde as a sterilant was avoided. In antibody positive patients mean haematocrit rose significantly (p less than 0.05), whereas in none of the antibody negative patients a definite change of haematocrit occurred. The data demonstrate, that formaldehyde sterilisation of dialysers may cause antibody-mediated haemolysis contributing to the extent of renal anaemia. This immunohaemolysis may be corrected, in spite of continuing antibody persistance, when formaldehyde exposure is totally avoided, or possibly when minimized.

The role of formaldehyde in the formation of haemodialysis-associated anti-N-like antibodies

In the sera of 68 (20.9%) of 325 haemodialysis patients, a specific cold agglutinin, cross-reacting with anti-N, was detected. Each patient showing this anti-N-like antibody used a formaldehyde-sterilized dialyser. By contrast, the antibody was not found in any of the 73 patients using a non-formaldehyde-sterilized dialyser. The results of transfusion experiments indicate an in vivo haemolytic activity of the antibody. In vitro, formaldehyde pretreatment of erythrocytes increased the agglutinability of the cells by the anti-N-like antibody. This effect could be prevented when the MN receptor of the red cells was exposed to neuraminidase. Trace quantities of formaldehyde inevitably enter the patient during dialysis when a formaldehyde-sterilized dialyser is used. It is postulated that this in vivo formaldehyde exposure might interact with the MN receptor of the red cells, rendering it immunogenic, and thus induce the formation of the haemodialysis-associated anti-N-like antibody.