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| Naturally occurring anti-P1 with high thermal amplitude complicating ABO blood grouping |
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Shirin Ferdowsi1, Saeed Mohammadi2, Moharram Ahmadnezhad1, Fahimeh Herfat1, Azita Rezvani1, Peyman Eshghi3, Arezoo Oodi1
1 Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran
2 Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine; Hematology-Oncology and Stem Cell Transplantation Research Center; Research Institute for Oncology, Hematology and Cell Therapy, Tehran University of Medical Sciences, Tehran, Iran
3 Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine; Pediatric Congenital Hematologic Disorders Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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| Date of Submission | 29-Jan-2021 |
| Date of Decision | 09-Jun-2021 |
| Date of Acceptance | 18-Jul-2021 |
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 Abstract | | |
Anti-P1 is immunoglobulin M type and occurs naturally; it is often detected as a weak- and cold-reactive antibody. However, in rare cases, it is reactive at 37°C or shows hemolytic transfusion reactions. The presence of high thermal amplitude of anti-P1 cannot be ignored and requires cross-match compatible red blood cells for transfusion. In the present study, we report three cases with ABO discrepancy due to anti-P1 that was identified as a cold-reacting antibody with high thermal amplitude.
Keywords: Blood group discrepancy, cold antibody, high thermal amplitude
How to cite this URL:
Ferdowsi S, Mohammadi S, Ahmadnezhad M, Herfat F, Rezvani A, Eshghi P, Oodi A. Naturally occurring anti-P1 with high thermal amplitude complicating ABO blood grouping. Asian J Transfus Sci [Epub ahead of print] [cited 2023 Mar 24]. Available from: https://www.ajts.org/preprintarticle.asp?id=345972 |
| Introduction | |  |
Anti-P1 is a naturally occurring antibody that is often present in P2 individuals. This antibody is a clinically insignificant immunoglobulin M (IgM) antibody that does not react at temperatures above of 25°C. However, in rare cases, it is reactive at 37°C or shows hemolytic transfusion reactions (HTRs).[1],[2],[3] The presence of high thermal amplitude of anti-P1 cannot be ignored and requires cross-match compatible red blood cells (RBCs) for transfusion. Here, we report three rare cases presented as blood group discrepancy due to naturally occurring anti-P1 that reacts at 37°C and antihuman globulin (AHG) phase.
| Case Reports | | |
Case presentation 1
A request for two units of packed red cells was received at the blood bank for a 61-year-old male patient. Medical history revealed that the patient is a known case of gastric cancer. There was no history of blood transfusion and chemotherapy was not started yet. Forward grouping showed A Rh positivity, while reverse blood grouping showed positive reactivity with A1 and B cells using the tube method [Table 1]. Because this serologic picture can be observed in a case with an A2 phenotype, the RBC was tested with anti-A1 lectin (Immucor). The RBC was positive for A1. Therefore, it is concluded that the unexpected reactivity in the reverse typing was not attributed to anti-A1. The patient serum was tested with a three-cell screen panel (Immucor) and showed a strong reaction to cell I and II at room temperature (RT), 37°C and AHG phase. Identification of antibody was done using 11-cell identification panel (Immucor) and pattern clearly, suggesting of anti-P1 [Figure 1]. Direct antiglobulin test (DAT) and autocontrol were negative. Red cell phenotype of the patient was also performed and showed the absence of the P1 antigen. To differentiate the immunoglobulin class of anti-P1, the patient's plasma was treated with dithiothreitol (DTT) and the antibody was found to be of IgM type. Neutralization of anti-P1 in the patient's plasma was performed using commercially available P1 substance (Immucor). Neutralized serum was used for reverse grouping, and blood group was confirmed to be A positive. In addition, patient's serum and P1-positive RBCs were tested only in the indirect antiglobulin test (IAT) phase, without reading at Immediate Spin (IS) and 37°C that showed positive reactivity. Because cross-match was incompatible due to the presence of cold antibody, prewarmed technique was used. The patient serum was placed into one tube and the reagent RBC was placed in the separate tube. All were warmed to 37°C, and then, 2 drops of prewarmed serum was transferred to a tube containing prewarmed red cells. Tubes were incubated at 37°C for 30 min. After washing three times with 37°C saline, anti-IgG was added according to the manufacturer's direction. No agglutination at the end of the procedure would be considered as negative cross-matching. Consequently, anti-P1 was identified as a cold-reacting antibody with high thermal amplitude, and P1 antigen-negative units were prepared for transfusion to avoid any risk. These units were IAT compatible in cross-match and transfusion was uneventful. | Figure 1: Antigram of 3 cells and 11 cells panels used in antibody identification (anti P1 Antibody)
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Case presentation 2
A 64-year-old female (gravida 8, para 8) with no history of blood transfusion was admitted in the hospital for surgery. On blood grouping, the patient's forward grouping was “A” and reverse was “O” using the tube method [Table 1]. Anti-A1 was ruled out after confirming the RBCs tested as group A1. The patient's IAT was found to be positive, while DAT and autocontrol were negative. Antibody screening and identification were performed using the tube method (3-cell and 11-cell panel), and anti-P1 was identified in the patient's plasma. To differentiate the immunoglobulin class of anti-P1, the patient's plasma was treated with DTT. Abrogation of reactivity with DTT treatment suggests that the anti-P1 was the IgM class. To confirm the antibody specificity, three red cells positive for the P1 antigen and three cells negative for the P1 antigen were crossing matched with the patient's serum. The results showed a reaction to the positive cells and no reaction with negative cells for this antigen. Neutralization of anti-P1 in the patient's plasma was performed, and reverse blood grouping was repeated using this serum. The patient's blood group was determined as A Rh negative. Red cell phenotype of the patient also showed the absence of the P1 antigen.
Case presentation 3
Forward grouping showed the AB-positive blood group and reverse grouping showed 3+ agglutination with A cells using the tube method in a 33-year-old woman with no history of blood transfusion and pregnancy. Antibody screening and identification was done with 3-cell and 11-cell panel, respectively. Three-cell panel was positive with cell III at RT, 37°C and AHG phase but was positive with the cell I and II just at RT. The 11-cell panel identified anti-P1. DTT treatment of the patients' serum was done, and the reaction in the P1-positive cell of the screening panel was abolished. This suggested that the antibody was IgM and not IgG and therefore probably naturally occurring. Discrepancy in blood grouping was eliminated after neutralization of serum with commercially P1 substance, and blood grouping was confirmed as AB negative.
| Discussion | | |
In the present study, we observed positive reactions at RT, 37°C and AHG phase that indicated our patients had anti-P1 as a cold antibody with high thermal amplitude. For transfusion in these patients, P1 antigen-negative units were prepared. These units were IAT compatible in cross-match and transfusion was uneventful. The anti-P1 was a naturally occurring IgM antibody and not an immune-type antibody since our patients did not have any past history of transfusion.
In a study that was reported by Ackley et al.,[4] a blood donor (a 63-year-old woman) with ABO typing discrepancy was identified due to anti-P1 with reactivity in RT. In another study, Smith et al.[2] identified a case with mild HTR due to an IgM anti-P1 reactive at 37°C. Additional cases with complement-binding antibodies against the P1 antigen reacting at 37°C and causing both immediate and delayed HTRs have been reported.[3],[5]
| Conclusion | | |
The clinically significant antibodies are those active at 37°C or in the AHG phase. Cases that reported in the present study showed that anti-P1 is a significant antibody that can cause discrepancy in ABO blood grouping and cross-match incompatibility. Therefore, our study highlights the importance of detecting the high thermal amplitude of anti-P1. For transfusion in these patients, RBC units that is compatible on the antiglobulin cross-match is necessary.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
| 1. | Thakral B, Bhattacharya P, Agnihotri N, Sharma R, Marwaha N, Gopalan S. Acute hemolytic transfusion reaction by anti-P1 antibody in pregnancy. Am J Hematol 2005;78:163-4.  |
| 2. | Smith D, Aye T, Er LS, Nester T, Delaney M. Acute hemolytic transfusion reaction due to anti-P1: A case report and review of institutional experience. Transfus Med Hemother 2019;46:380-3. |
| 3. | Arndt P, Garratty G, Marfoe R, Zeger G. An acute hemolytic transfusion reaction caused by an anti-P1 that reacted at 37°C. Transfusion 1998;38:373-7. |
| 4. | Ackley RJ, Byrne KM, Weddington PE. Anti-P1: Don't miss the obvious. Immunohematology 2007;23:130-2. |
| 5. | Girelli G, Pupella S, Perrone MP, Screnci M. Transfusion reaction caused by anti-P1 antibody. Transfus Sci 1993;14:405-7. |
Correspondence Address:
Arezoo Oodi,
Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran
Iran
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/ajts.ajts_12_21
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