Routine Pretransfusion Testing Research Articles

Routine pretransfusion testing before primary total hip or knee arthroplasty are an expensive and wasteful routine. Systematic review and meta-analysis.

The excessive routine ordering of pretransfusion tests (blood typing, screening, and cross-matching) for surgical cases incurs significant unnecessary costs and places an undue burden on transfusion services. This study aims to systematically review the literature regarding the necessity of routine pretransfusion tests before total hip arthroplasty (THA) or total knee arthroplasty (TKA) and summarize their outcomes. A systematic review and meta-analysis were performed. The study's characteristics, the prevalence of over-ordering pretransfusion tests, transfusion rates, and potential cost savings to the healthcare system were analyzed. The study included 17,667 patients. Pooled results revealed a 96.3% over-ordering pretransfusion test rate (95% CI: 0.92-1.00; p < 0.001) among patients undergoing primary THA or TKA. The pooled prevalence of hospital transfusion rate was 3.6%. Notably, there were statistically significant differences in preoperative hemoglobin (Hb) levels between patients not requiring transfusion (Hb = 13.9g/dl; 95% CI 12.59-15.20; p < 0.001) and those needing transfusion (Hb = 11.9g/dl; 95% CI 10.69-13.01; p < 0.001) (p = 0.03). The per-patient total cost savings ranged from 28.63 to 191.27 dollars. Our study suggests that routine pre-transfusion testing for all patients undergoing primary THA or TKA may be unnecessary. We propose limiting pretransfusion test orders to patients with preoperative hemoglobin levels below 12g/dl in unilateral primary TKA or THA. This targeted approach can result in significant cost savings for healthcare systems and transfusion services by reducing the over-ordering of pretransfusion tests in these surgical procedures.

Characterization of Novel RHD Allele Variants and Their Implications for Routine Blood Group Diagnostics.

The Rh system, including the highly immunogenic D antigen, is one of the clinically most important blood group systems in transfusion medicine. Numerous alleles of the RHD gene are associated with variant RhD phenotypes. In case of Rh incompatibility, some of them can induce hemolytic transfusion reactions and hemolytic disease of the fetus and newborn. Thus, accurate blood group diagnostics are critical for safe transfusion therapy. We characterized phenotypes of four individuals revealing weakened D expression during routine pre-transfusion testing. Standard gel card matrix techniques with monoclonal and polyclonal anti-D antibodies were used for serological typing, complemented using D epitope and antigen density analysis. Genotyping employing PCR with sequence-specific primers, genomic and allele-specific Sanger sequencing and in silico protein analysis were performed. Four novel RHD alleles associated with weak D or partial D phenotypes were identified. One of the mutations is predicted to disrupt the terminal stop codon and result in an elongated translation of the mutant D protein that phenotypically exhibits a loss of D epitopes. Furthermore, a hybrid gene formed with the homologue RHCE gene is described. The presented data enhances the understanding of the Rh system and may contribute to continued advances in blood group diagnostics.

The CD47-Blocking Immune Checkpoint Inhibitor Maplirpacept Does Not Interfere with Blood Transfusion Compatibility Testing

CD47 is a transmembrane glycoprotein that delivers an anti-phagocytic (“do-not-eat”) signal by binding to signal regulatory protein α (SIRPα) on the surface of macrophages. Many tumors express high levels of CD47 as a means to escape macrophage-mediated immune surveillance and blockade of the CD47-SIRPα pathway has emerged as a novel therapeutic strategy with demonstrated anti-tumor activity both in vitro and in vivo (Petrova et al. 2017; Weiskopf 2017). Maplirpacept (PF-07901801, TTI-622) is a soluble human SIRPαFc fusion protein with an IgG4 domain which acts as an innate immune checkpoint inhibitor that prevents CD47-SIRPα binding, engages activating Fcγ receptors on macrophages, and promotes phagocytosis of malignant cells (Lin et al. AACR 2018). Maplirpacept is currently in clinical development to treat patients with ovarian cancer, multiple myeloma, acute myeloid leukemia and lymphoma. Additionally, CD47 is expressed on red blood cells (RBCs) and plays a role in the natural clearance of aged RBCs by splenic macrophages in vivo (Oldenborg et al. 2000). CD47 expression on RBCs was shown to interfere with pre-transfusion laboratory testing in patients treated with the anti-CD47 mAb, Hu5F9-G4 (Velliquette et al. 2019). Unlike anti-CD47 mAbs, minimal binding to human RBCs is observed with Maplirpacept (Lin et al. AACR 2018). In this study we investigated whether the minimal binding of Maplirpacept to human RBCs precludes interference with routine pre-transfusion laboratory tests. RBC suspensions from healthy donors representing all 8 ABO-Rh blood groups were spiked with Maplirpacept at 0.6, 1.2 or 2 mg/ml or anti-CD47 (clone Hu5F9). Blood typing was performed according to the manufacture's protocol (Seraclone, Biorad) and observed for the presence or absence of agglutination. For cross matching experiments, plasma was prepared from blood of healthy donors and spiked with Maplirpacept or anti-CD47 at the same concentrations used for the blood typing experiments. RBCs from two healthy donors were mixed with plasma and an indirect antiglobulin test (IAT) was performed according to the manufacture's protocol (Coombs Anti-IgG, Biorad). Using RBCs from healthy donors representing the 8 major ABO-Rh blood groups, we now show that the addition of Maplirpacept does not cause agglutination of test RBCs and produces the expected blood typing result in a standard forward blood typing test. No interference was observed at the highest concentration tested. However, addition of an anti-CD47 mAb caused pan-agglutination as well as false positive blood typing results (Table 1). In a standard IAT that mimics the in vitro compatibility cross matching test performed prior to a blood transfusion, the anti-CD47 mAb gave false positive results while Maplirpacept produced results identical to the control serum condition (Table 2). This data is consistent with a study demonstrating interference by Hu5F9 in routine pre-transfusion blood testing (Velliquette et al. 2019). Additionally, no interference was observed when Maplirpacept was added to conditions which produced agglutination in a standard IAT across a range of blood types. Interference with RBC panel testing has important consequences in transfusion medicine as the presence of irregular antibodies can complicate the selection of suitable RBC units for treated patients. Here we demonstrate that interference with blood compatibility testing is dependent upon the type of CD47-blocking agent. Decoy receptors such as Maplirpacept, unlike anti-CD47 mAb, do not interfere with blood group serologic testing, which may confer a significant clinical advantage by negating the need for additional approaches to prevent interference.

A rapid ABO and RhD test demonstrates high fidelity to blood bank testing for RhD typing.

The rapid provision of blood products is life-saving for patients with massive hemorrhage. Ideally, RhD-negative blood products would be supplied to a woman of childbearing potential whose Rh type is unknown due to the risk of D-alloimmunization and the potential for hemolytic disease of the fetus and newborn to occur if RhD-positive blood products are transfused. Therefore, there is a need for a test that rapidly determines her RhD type. This study compared the RhD type determined using a rapid ABO and RhD test to the RhD type determined by an immunohematology reference laboratory. After receiving ethics review board approval, 200 random, unique, deidentified patient samples that had undergone routine pretransfusion testing in an immunohematology reference laboratory using column agglutination technology were collected and tested using a rapid ABO and RhD test (Eldoncard Home kit 2511). The RhD typing results from these two methods were compared to determine the accuracy of the rapid ABO and RhD test. The rapid ABO and RhD test produced results that were concordant with the transfusion service's results in 199/200 (99.5%) of cases, with a negative predictive value of 98.2% and 99.3% sensitivity. The single outlier was likely an RhD variant due to its serological characteristics. These data indicate that this rapid ABO and RhD test could be used for the rapid determination of a patient's RhD type, perhaps even in the emergency department, which could guide the selection of blood products provided during their resuscitation.

A rare case of clinically significant naturally occurring anti-Cw reported in a healthy male donor.

Anti-Cw antibody is an immunoglobulin against the red cell antigen Cw which is a low frequency red cell antigen that belongs to the Rh antigen system. It is a clinically significant antibody and may cause haemolysis on exposure to antigen positive red cells. Due to its low frequency, it is not included in routine antibody screening panels. A 32years healthy male donor with no history of transfusion donated whole blood at the department of Transfusion Medicine & Blood Centre of our institute. As a part of routine pre-transfusion testing, the donor's samples were subjected to automated blood grouping and screening for unexpected red cell antibodies using 3 cells panel on solid-phase red-cell adherence (SPRCA) (Galileo Neo, Immucor, Norcross, USA). The antibody screening came out to be positive with a reaction in cell I of the antibody screening panel. Further the antibody was identified as anti Cw in using 16 cells panel, select cells and phenotyping. In the present case, the anti-Cw antibody was found to be reactive at 37°C and AHG phase which could lead to haemolytic transfusion reaction. The fact that the male donor had no history of transfusion or transplant led us to the conclusion that it was a naturally occurring, but a clinically significant antibody. This case highlights the importance of performing an antibody screening for healthy donors as well and urges transfusion services to procure screening cells which incorporate Cw positive cells.

Evaluating patients with autoimmune hemolytic anemia in the transfusion service and immunohematology reference laboratory: pretransfusion testing challenges and best transfusion-management strategies

The serologic evaluation of autoimmune hemolytic anemia (AIHA) confirms the clinical diagnosis, helps distinguish the type of AIHA, and identifies whether any underlying alloantibodies are present that might complicate the selection of the safest blood for any needed transfusion. The spectrum of testing is generally dependent on the amount and class (immunoglobulin G or M) of autoantibody as well as the resources and methodologies where testing is performed. The approach may range from routine pretransfusion testing, including the direct antiglobulin test, to advanced techniques such as adsorptions, elution, and red cell genotyping. When transfusion is needed, the selection of the optimal unit of red blood cells is based on urgency and whether time allows for the completion of sophisticated serologic and molecular testing methods. From the start of when AIHA is suspected until the completion of testing, communication among the clinical team and medical laboratory scientists in the transfusion service and immunohematology reference laboratory is critical as testing can take several hours and the need for transfusion may be urgent. The frequent exchange of information including the patient's transfusion history and clinical status, the progress of testing, and any available results is invaluable for timely diagnosis, ongoing management of the patient, and the safety of transfusion if required before testing is complete.

Is routine blood typing and screening necessary before primary total hip or knee arthroplasty in the 21st century?

Blood loss warranting transfusion is a relatively rare complication of major-joint arthroplasty procedures like total knee arthroplasty (TKA) and total hip arthroplasty (THA). Despite this rarity, pre-transfusion testing (blood typing, screening, and cross-matching) has become routine. We sought to determine if such routine testing is necessary for patients who undergo a primary TKA or THA by (1) measuring the current rate of intraoperative transfusions in primary TKA and THA patients, (2) identifying risk factors for transfusions, and (3) calculating the costs of such blood typing and screening. We retrospectively examined the records of 992 patients who underwent primary TKA, THA, or unicompartmental knee arthroplasty (UKA) to identify patients requiring intra-operative or in-hospital postoperative transfusions. Demographic and baseline clinical and laboratory data also were collected and analyzed to identify predictors of transfusion. Cost analysis was performed. The rate of intraoperative transfusion was 1.7% (17/992 patients), with rates of 2.1%, 1.6%, and 0% for TKA, THA, and UKA respectively. The in-hospital transfusion rate was 10.3%, with corresponding postoperative transfusion rates of 9.1%, 12.9%, and 2%. The only baseline variable significantly linked to transfusions on multivariable analysis was preoperative hemoglobin level, with preoperative Hgb <12 g/dl predictive of transfusions in both TKA (p=.02) and THA (p=.024) patients. Our study suggests that pre-transfusion testing for all patients undergoing primary UKA, TKA or THA is unnecessary. We recommend reserving routine pre-transfusion testing for patients with preoperative hemoglobin levels below 12 g/dl.

Recent advances in blood group genotyping

: Red blood cell (RBC) antigen typing of both recipients and donors is vital for safe and effective transfusion. Despite the existence of >330 RBC antigens, current routine pre-transfusion testing only includes matching the patient and donor for ABO and D, since serologic typing methods are difficult to scale for routine non-ABO/D antigen typing (i.e., extended antigen typing). While PCR-based genotyping can be used to broadly genotype most antigens, current assay formats limit the number of genetic changes and samples that can be simultaneously tested (~50 genetic changes and ~100 samples per run). However, the emergence of RBC antigen genotyping using next-generation sequencing (NGS) and high-density DNA arrays have the potential to overcome many of these limitations. NGS allows an unprecedented evaluation of genetic changes including novel genetic changes and complex structural variations (SVs), representing the new gold standard for RBC antigen genotyping. High-density DNA arrays allow for low cost evaluation of all known genetic changes including SV with the ability to run 1,000s of samples at a time. As such, NGS will likely replace conventional PCR genotyping for discordants and complex serologic workups and offer an unprecedented level of discovery for new RBC antigens. High-density DNA arrays have the potential to allow for routine genotyping of all blood donors for all genetically understood antigens, something that will fundamentally change the practice of transfusion medicine.

Red cell alloimmunization in multitransfused chronic renal patients on haemodialysis in a tertiary care centre of Jammu region

Background: There is a high incidence of alloimunization in many patients with diseases that require repetitive blood transfusions. One such group is chronic renal failure patients as majority of them have severe anemia due to deficiency of erythropoietin. As many such patients are unable to afford erythropoietin, they are treated with blood transfusions. This study was thus undertaken to study alloimunization in such patients at our center.Methods: A total of 96 patients found eligible were enrolled in this cross-sectional study that was carried out from June 2016 to august 2016. After detailed history, antibody screening was done by using Immucor Panoscreen three vial set and if screening came out to be positive antibody identification was then done by using Immucor Panocell-10.Results: 96 patients including 76 male and 20 female patients recieved a total of 912 transfusions. Alloantibodies were detected in a total of 12 patients (12.5%). Of these 12 patients 8 patients had a single antibody whereas 4 patients developed two antibodies. The antibodies developed at a rate of 1.8% per transfusion (16/912). On alloantibody type identification, the most common type found was anti E (4/16) followed by both anti D and anti C in 3 patients each.Conclusions: Alloimmunization to minor erythrocyte antigens occurs in many patients of chronic renal failure. This results in frequent pre-and post-transfusion complications. Inclusion of antibody screening test in routine pretransfusion testing protocol for the patients who are at higher risk of alloimmunization and require long-term transfusion dependence is desirable.

Screening and identification of red blood cell alloantibodies among hemodialysis patients in National Institute of Urology and Nephrology

Background It is well known that alloimmunization to red blood cell antigens resulting from the genetic disparities between the donor and the recipient is one of the risks of blood transfusion. Alloimmunization can result in clinical hemolysis and difficulty in cross-matching blood. The risk of alloimmunization is higher in patients who have received multiple blood transfusions such as renal failure patients on dialysis who receive blood transfusions. The antibody-screening test (2–3 cells panel) used to detect unexpected antibodies is not a mandatory pretransfusion testing in our blood bank of National Institute of Urology and Nephrology (NIUN), and is performed routinely in limited blood centers. Aim This study was conducted to screen and identify different types of red cell alloantibodies and the factors influencing the development of alloantibodies among patients on dialysis in NIUN. Patients and methods This study was conducted in the blood bank of NIUN, Egypt. A total of 192 patients (102 males and 90 women) who were diagnosed to have chronic renal failure, on regular hemodialysis for at least 1 year, their age more than 20 years, anemic (hemoglobin Results Red cell alloantibodies were detected in 10 (5.2%) patients (two men and eight women). The prevalence of alloantibodies detected in patients with positive results were anti-E (2.1%), anti-K (1.6%), antibodies of unknown specificity (1.6%), and antibody against high-incidence antigen (0.5%). There was a significant difference between sex and the number of blood units transfused with alloimmunization (P = 0.048 and 0.037, respectively). Conclusion The prevalence of alloimmunization among chronic renal failure patients on dialysis was 5.2%. The most common alloantibodies were anti-E (the Rhesus system) (2.1%) and anti-K (the Kell system) (1.6%) and the risk of alloimmunization is known to be influenced by the recipient sex (more in females) as well as the number of blood units transfused. So, antibody screening and identification tests are recommended as a routine pretransfusion testing protocol at least for the patients who are at higher risk of alloimmunization and require long-term transfusion dependence, which will definitely add significant value in blood safety.

Prevalence of red blood cell antibodies among transfused patients at Komfo Anokye teaching (Kath) hospital, Ghana

Red blood cell (RBC) alloimmunisation is a common problem in transfused patients because of the possibility of haemolytic reaction and limited availability of compatible blood. In highincome countries, pre-transfusion antibody screening is performed routinely. In Ghana, patients are transfused with ABO Rh ‘D’ compatible blood without screening for immune antibodies. We therefore studied the prevalence and specificities of RBC antibodies in transfused patients at Komfo Anokye Teaching hospital, Ghana. The study was cross-sectional, involving previously transfused patients who required another transfusion. Participants’ basic data on demography and transfusion history were recorded. Blood samples were screened and subsequently typed for RBC antibodies using a column gel agglutination test. A total of 106 transfused patients, 52 male and 54 females were enrolled. The patients had previously received a median of 4 RBC units (range 1-14). Of these, ten patients (9.4%) had 11 RBC alloantibodies, whose specificities were 2 anti-K; 2 anti-C; one each of anti-D, -E, -M, and -S; and 3 were pan-reactive. The number of transfusion episodes was significantly associated with the rate of alloimmunisation (p=0.000). In conclusion the overall alloimmunisation rate in the study was 9.4% and this was significantly associated with increasing number of transfusion episodes. Antibodies were mainly directed against antigens in the Rhesus system and K antigen. We recommend that antibody screening be incorporated into routine pre-transfusion testing procedures in Ghana. Keywords: Alloimmunisation, multi transfusion, Alloantibody

An experience of the introduction of a blood bank automation system (Ortho AutoVue Innova) in a regional acute hospital

This paper reports on an evaluation of the introduction of a blood bank automation system (Ortho AutoVue® Innova) in a hospital blood bank by considering the performance and workflow as compared with manual methods. The turnaround time was found to be 45% faster than the manual method. The concordance rate was found to be 100% for both ABO/Rh(D) typing and antibody screening in both of the systems and there was no significant difference in detection sensitivity for clinically significant antibodies. The Ortho AutoVue® Innova automated blood banking system streamlined the routine pre-transfusion testing in hospital blood bank with high throughput, equivalent sensitivity and reliability as compared with conventional manual method.

Efficiency of RBC Antibody Detection Methods: Comparison of Manual Indirect Antiglobulin Test (IAT) to a Method Using Very Low Ionic Strength Conditions (vLIS/IAT).

Abstract 2276Is has long been known that RBC antibody detection is enhanced following a decrease in the ionic concentration. In the past we added into our routine pre-transfusion antibody screen a new test, which employs ionic strength conditions between 15 to 17% of the ionic strength of 0.9% NaCl (vLIS/IAT): 2 drops of patient's plasma and one drop of 3% RBC are incubated for 15 minutes in 0.5 mL of 5% mannitol, pH 6.0 with phosphate buffer, containing 8mM EDTA. The RBCs are washed with normal saline and tested for agglutination by an anti-IgG reagent. Other published low ionic strength methods decrease the ionic concentration less, up to about 50%.In the process of pre-transfusion testing we found 711 patients with one, two or more blood group antibodies. The following table shows the specificities and quantities of clinically significant antibodies detected by these two methods. The following antibody specificities were not included: those that were present only in small quantities, directly agglutinating IgM antibodies and anti-Lea and Lebantibodies which are usually considered to be clinically insignificant.Antibody specificityTotal Number detected% Detected by IAT% Detected by vLIS/IATC7171.8%93.0%c3680.5%92.0%D14768.7%97.3%E22040.3%95.5%Fya4470.5%95.5%Jka6060.0%96.7%K15489.0%76.0%M2334.8%87.0%S1850.0%100%Total773Avg. 62.8%Avg. 92.6%Overall, vLIS/IAT detected an increase in clinically relevant antibodies compared to IAT. This is clearly seen in the case of anti-E, anti-D, anti-Jka, anti-M and anti-S antibodies. Anti-K antibodies, however, were detected preferably by IAT. It should be noted that more anti-Le antibodies, although not shown here, were detected either by IAT or by direct agglutination (IgM antibodies).In summary, these data show that vLIS/IAT improved antibody detection when incorporated into routine pre-transfusion tests. They also indicate that one method does not detect all clinically significant antibodies; therefore it is beneficial to use two methods which in combination cover the varying spectra of RBC antibodies. Disclosures:No relevant conflicts of interest to declare.

Antibody elutions in Thai patients with a positive direct antiglobulin test.

The direct antiglobulin test is performed to determine whether an anaemic patient with evidence of haemolysis has autoimmune or alloimmune haemolytic anaemia. We determined the antibody specificity of eluted IgG antibodies from patients' blood samples with a positive direct antiglobulin test. Overall, 134 Thai patients were included in this study. EDTA blood samples were obtained from recently transfused patients, patients with unexplained anaemia and patients who had serum antibodies detected during routine pre-transfusion tests from different hospital blood banks. These complicated samples were sent to the National Blood Centre of the Thai Red Cross Society for investigation and to find compatible blood components. Each blood sample underwent a direct antiglobulin test with the gel technique using polyspecific antihuman globulin and mononospecific anti-IgG and anti-C3d. Acid eluates were prepared from the samples for which the direct antiglobulin test was positive and the specificities of the eluted antibodies were determined by the gel technique. Of the samples tested, 101 showed a positive direct antiglobulin test result (75.4%) using polyspecific antihuman globulin sera whereas only 95 samples (70.9%) were positive with anti-IgG or anti-IgG and anti-C3d. Moreover, 54 of 95 eluates (56.8%) were positive for antibody screening and tested with the reagent panel cells. Twenty-one eluates had specific alloantibodies, which were concordant with the findings in the patients' sera and all patients had a history of blood transfusion. Additionally, 33 eluates contained pan-agglutinins. Interestingly, alloantibodies could be determined using titration studies in 5 of 26 eluates with pan-agglutinins. Although the direct antiglobulin test is not routinely performed in pre-transfusion screening, this test and elution studies would be useful in patients with a history of previous transfusions, and in those for whom compatible blood cannot be found.

LETTERS TO THE EDITOR: Comparison of three low‐ionic‐strength solutions for routine pretransfusion testing: antibody screening/identification, cross‐matching, immune anti‐ABO detection, and direct antiglobulin tests

LETTERS TO THE EDITOR: Comparison of three low‐ionic‐strength solutions for routine pretransfusion testing: antibody screening/identification, cross‐matching, immune anti‐ABO detection, and direct antiglobulin tests

Les phénotypes érythrocytaires rares : un enjeu de santé publique

A rare blood group is usually defined as the absence of a high prevalence antigen or the absence of several antigens within a single blood group system, if its prevalence in France is 4/1000 or less in the general population. An individual with a rare blood phenotype can develop a naturally-occurring or immune antibody corresponding to his rare specificity. In case an extremely low stock of compatible blood is available at the national level, a so-called “transfusion deadlock” is described. Most of the individuals with a rare blood group are coincidently identified when a routine pretransfusion testing or pregnancy follow-up is performed, if the antibody(ies) corresponding to the rare specificity is(are) present. Other individuals are discovered following a systematic red cell typing, or family investigations in siblings. One hundred and twenty-one rare blood specificities and 42 rare blood genotypes are currently defined at the French National Reference Laboratory for Blood Groups (CNRGS–Paris). The French national registry of individuals with a rare blood phenotype/genotype includes about 9600 people, who are urged to regularly donate blood for the National Rare Blood Bank. This bank, based on a homologous blood transfusion program, is in charge of the long-term storage of rare frozen blood units, that can only be delivered after receiving authorization from the CNRGS. The global and individual care management of the individuals with a rare blood group, concerning potentially several hundred thousand people in France, requires a close cooperation between all the protagonists within the transfusion chain.

Electronic Crossmatching

The crossmatch (XM) is an important part of routine pretransfusion testing. It is used to detect ABO incompatibility and other clinically significant antibodies. The XM has been modified many times and, in recent years, has been abbreviated. The 2 common types of XM currently being done are the immediate spin XM for antibody-negative patients and the antiglobulin XM for the rest. The antiglobulin phase of the XM is generally considered optional, unless a clinically significant antibody is present. Originally, the XM was intended to be a final check for ABO compatibility and for the detection of unexpected antibodies. Electronic crossmatching was first introduced at the University of Michigan Medical Center in 1992. This paper summarizes the basic principles, current guidelines, regulatory requirements, and some recommendations that may prove useful for the implementation of electronic crossmatching.

Cesarean section: Is pretransfusion testing for red cell alloantibodies necessary?

Routine pretransfusion testing for red cell alloantibodies (RBCab) in cesarean patients is standard practice in many obstetric centers. The objective of the present study was to evaluate the usefulness of this test. A retrospective study was conducted using computerized registers to extract data on blood transfusions and the occurrence of RBCab in cesarean patients. A total of 4434 admissions for cesarean section were identified. Only 10 patients (0.23%) had clinically significant RBCab, which had not been previously detected. Blood transfusions were required in relation to 147 cesarean sections (3.3%). A number of preoperative conditions, traditionally believed to be risk factors for preoperative and postpartum hemorrhage, occurred more frequently in transfused patients than in nontransfused. The probability of a cesarean patient having a previously undetected clinically significant RBCab and receiving a blood transfusion during admission for delivery was estimated to be 9.0 x 10(-5) (1 in 11 050 cesarean sections). Analyses of the time relationships between cesarean sections and initiation of blood transfusions indicated that most often there would be enough time for postoperative antibody screening and/or cross matching if the routine pretransfusion testing was omitted. These findings suggest that routine pretransfusion testing in cesarean patients can be omitted.

The gel test: sensitivity and specificity for unexpected antibodies to blood group antigens

The recently FDA-licensed anti-IgG gel test for pretransfusion antibody detection requires crossover validation before implementation. Six hundred coded samples sent for routine pretransfusion tests were used to compare GEL (ID-MTS, Ortho Diagnostic Systems Inc., Raritan, NJ) with Löw and Messeter's low-ionic-strength saline (LISS). There were 456 GEL-LISS-, 97 GEL+LISS+, 45 GEL-LISS+, and 2 GEL+LISS- tests. The 144 positive tests involved 157 antibodies; 67 of these (cold auto, anti-M, -Le, etc.) were considered harmless with respect to transfusion management. GEL-LISS+ tests included seven samples containing potentially significant antibodies (assumed from specificity): anti-K(4), -Jka, -Fyb, and -S. Two potentially significant antibodies (anti- C and -D) were GEL+LISS-. Sensitivity and specificity for potentially significant antibodies were 92% and 96% for GEL, and 98% and 90% for LISS, respectively. The seven GEL-LISS+ samples associated with potentially significant antibodies were from six patients. Five of these antibodies, all detected in immune-suppressed patients, reacted predominantly as agglutinins in LISS. None of these seven antibodies were detected reliably by polyethylene glycol and LISS-additive tube methods. In light of the immune status of the patients with GEL-LISS+ agglutinins with specificity normally considered potentially significant, and because other valid methods did not detect these antibodies, their clinical importance is questionable. Excluding these questionable antibodies, GEL has the same sensitivity and better specificity than LISS. GEL is a valid method for pretransfusion antibody detection.

Lack of clinical significance of "enzyme-only" red cell alloantibodies.

In a retrospective study on samples from 10,000 recently transfused patients, 35 samples were found to contain an antibody that reacted with ficin-treated red cells but was not demonstrable by low-ionic-strength saline solution and indirect antiglobulin test (LISS-IAT). In those 35 patients, the specificity of the antibody was such that each patient would have been transfused with antigen-negative blood had the antibody reacted in LISS-IAT. Tests on red cells from the units already transfused showed that 19 patients had among them received, by chance, 32 antigen-positive and 74 antigen-negative units. The remaining 16 patients had among them received 57 units that were, again by chance, all antigen negative. One patient given antigen-positive blood suffered a delayed transfusion reaction; in two others the antibodies became LISS-IAT active after transfusion. However, similar changes to the LISS-IAT-active state were seen with two antibodies of patients given only antigen-negative blood. Also found in the 10,000 patients were 28 clinically insignificant antibodies, 77 sera in which the antibody was too weak to identify, and 216 autoantibodies that reacted only with ficin-treated red cells. These data support a belief, generally held in the United States but not necessarily elsewhere, that the use of protease-treated red cells for routine pretransfusion tests creates far more work than the accrued benefits justify.