A primer in pretransfusion testing

Pretransfusion testing encompasses much more than testing a patient's sample in the laboratory. All aspects pertaining to this testing will be reviewed, from the clinician's order to the final step of when the blood product is ready to be issued to the clinical side from the laboratory. The importance of patient safety and positive outcomes will be stressed through discussion of positive patient identification and appropriate labelling in order to get the right product to the right patient at the right dose. Transfusion service does not stop in the laboratory; it is imperative that all who are involved in this service appreciate the significance of performing tasks accordingly to standards and regulations.     

Incomplete pretransfusion testing leads to surgical delays

BACKGROUND: The Joint Commission has highlighted the importance of having appropriate and complete pretransfusion testing before surgery begins. The maximum surgical blood ordering schedule (MSBOS) indicates which patients require preoperative transfusion testing. We determined the number of times surgical delays were caused due to the lack of completed pretransfusion testing. STUDY DESIGN AND METHODS: All transfusion events reported through the common medical event reporting system of eight networked hospitals over a 12‐month period were evaluated to determine how often patients experienced surgical delays due to not having complete pretransfusion testing. RESULTS: During this 12‐month period 12 patients were identified who were either in or en route to the operating room with incomplete pretransfusion testing leading to a delay in providing crossmatched red blood cells (RBCs). In 6 of 12 cases a new antibody was discovered, which required extra time for the provision of crossmatched RBCs, while in 4 of 12 patients the samples were not sent or were lost on the way to the blood bank. In the remaining two patients other parts of the pretransfusion testing process were not followed according to hospital policy. The median surgery start time delay was approximately 12 hours (range, 1‐168 hr) in 11 of 12 cases. One patient's case was not aborted when it was discovered that crossmatched RBCs were not immediately available due to newly detected alloantibodies. CONCLUSIONS: We identified three mechanisms by which delays in completing pretransfusion testing in surgical patients occurred. Adherence to the MSBOS and sample collection policies should reduce delays.     

Exponential error reduction in pretransfusion testing with automation

BACKGROUND: Protecting the safety of blood transfusion is the top priority of transfusion service laboratories. Pretransfusion testing is a critical element of the entire transfusion process to enhance vein‐to‐vein safety. Human error associated with manual pretransfusion testing is a cause of transfusion‐related mortality and morbidity and most human errors can be eliminated by automated systems. However, the uptake of automation in transfusion services has been slow and many transfusion service laboratories around the world still use manual blood group and antibody screen (G&S) methods. STUDY DESIGN AND METHODS: The goal of this study was to compare error potentials of commonly used manual (e.g., tiles and tubes) versus automated (e.g., ID‐GelStation and AutoVue Innova) G&S methods. Routine G&S processes in seven transfusion service laboratories (four with manual and three with automated G&S methods) were analyzed using failure modes and effects analysis to evaluate the corresponding error potentials of each method. RESULTS: Manual methods contained a higher number of process steps ranging from 22 to 39, while automated G&S methods only contained six to eight steps. Corresponding to the number of the process steps that required human interactions, the risk priority number (RPN) of the manual methods ranged from 5304 to 10,976. In contrast, the RPN of the automated methods was between 129 and 436 and also demonstrated a 90% to 98% reduction of the defect opportunities in routine G&S testing. CONCLUSION: This study provided quantitative evidence on how automation could transform pretransfusion testing processes by dramatically reducing error potentials and thus would improve the safety of blood transfusion.     

Evaluation of a new automated instrument for pretransfusion testing

BACKGROUND: A number of automated devices for pretransfusion testing have recently become available. This study evaluated a fully automated device based on column agglutination technology (AutoVue System, Ortho, Raritan, NJ). STUDY DESIGN AND METHODS: Some 6747 tests including forward and reverse ABO group, Rh type and phenotype, antibody screen, autocontrol, and crossmatch were performed on random samples from 1069 blood donors, 2063 patients, and 98 newborns and cord blood. Also tested were samples from 168 immunized patients and 53 donors expressing weak or variant A and D antigens. Test results and technician times required for their performance were compared with those obtained by standard methods (manual column agglutination technology, slide, semiautomatic handler). RESULTS: No erroneous conclusions were found in regard to the 5028 ABO group and Rh type or phenotype determinations carried out with the device. The device rejected 1.53 percent of tests for sample inadequacy. Of the remaining 18 tests with discrepant results found with the device and not confirmed with the standard methods, 6 gave such results because of mixed-field reactions, 10 gave negative results with A2 RBCs in reverse ABO grouping, and 2 gave very weak positive reactions in antibody screening and crossmatching. In the samples from immunized patients, the device missed one weak anti-K, whereas standard methods missed five weak antibodies. In addition, 48, 34, and 31 of the 53 weak or variant antigens were detected by the device, the slide method, and the semiautomated handler, respectively. Technician time with the standard methods was 1.6 to 7 times higher than that with the device. CONCLUSION: The technical performance of the device compared favorably with that of standard methods, with a number of advantages, including in particular the saving of technician time. Sample inadequacy was the most common cause of discrepancy, which suggests that standardization of sample collection can further improve the performance of the device.     

The evaluation of a positive direct antiglobulin test in pretransfusion testing

The results of serologic studies on 879 blood samples with a positive direct antiglobulin test (DAT) are presented. All blood samples were from patients who were either anemic, for reasons other than blood loss, recently transfused, or had serum antibodies detected during routine pretransfusion tests. Blood samples from only 81 of the patients included in this study had serologically reactive eluates (64 autoantibodies, three antibodies to penicillin and cephalothin treated red blood cells, three passively acquired anti-A antibodies, and 11 transfusion-induced alloantibodies). The eluted antibodies were also detected in the serum by routine pretransfusion tests in 13 of the patients whose red blood cells eluted autoantibodies, and in five of the patients whose red blood cells eluted transfusion-induced alloantibodies. All but one of the 11 transfusion-induced alloantibodies were detected within 14 days posttransfusion. Based on these findings, a cost-effective and safe approach to the management of blood samples with a positive DAT would be to restrict the preparation and testing of eluates to those samples from recently transfused patients. It is the contention of the authors that the incorporation of the DAT in pretransfusion testing should primarily serve to detect alloantibody formation before such antibodies are evident in the serum, and should not be used to screen patients for unsuspected autoimmune hemolytic anemia. Furthermore, the authors question the necessity for blood banks to routinely perform an autocontrol on all blood samples from prospective transfusion recipients.     

Suitability of preadmission blood samples for pretransfusion testing in elective surgery

BACKGROUND: North American transfusion guidelines do not stipulate a time limit between drawing the specimen for pretransfusion testing and giving the transfusion to patients who have not received a transfusion or been pregnant in the preceding 3 months. British guidelines suggest that separated plasma and serum can be stored at -30 degrees C for up to 6 months, but they draw attention to the paucity of evidence concerning the use of stored samples. In Australia, transfusion guidelines recommend a maximum of 10 days' validity for pretransfusion specimens, which requires the patient to present for pretransfusion testing within 10 days of admission or to undergo retesting after admission, which in turn necessitates additional time in the hospital before operation. The study was performed to document the safety of using for pretransfusion testing a blood sample collected more than 10 days before surgery. STUDY DESIGN AND METHODS: Samples from 500 patients scheduled for elective surgery who had not been pregnant or received a transfusion in the previous 3 months were separately tested in blood group and antibody screens at an interval from 11 to 335 days before admission and again on admission. RESULTS: No clinically significant change was detected in the red cell antibody status of the paired samples of any patient. CONCLUSION: For patients who have not been transfused or pregnant in the previous 3 months, it is safe to crossmatch blood for transfusion by using a sample collected well in advance of elective surgery and stored at -30 degrees C.     

Ebola virus disease,transmission risk to laboratory personnel,and pretransfusion testing

As Ebola virus has infected thousands of individuals in West Africa, there is growing concern about the appropriate response of hospitals in developed nations caring for patients and handling laboratory specimens for patients suspected of Ebola virus disease (EVD). Guidelines for caring for EVD patients are proliferating rapidly from national and state public health authorities, professional societies, and individual hospitals. It is no surprise that they differ from one another, and some very conservative recommendations call for suspension of routine laboratory testing, including pretransfusion testing. EVD is transmitted by direct contact with blood, secretions, organs, and other body fluids and not by airborne routes. Based on experimental and observational data, the US Centers for Disease Control and Prevention (CDC) recommends that clinicians follow contact and droplet precautions. Laboratory personnel are required to follow the blood‐borne pathogen standard, especially the use of appropriate barriers consisting of gloves, gown, goggles, mask to cover nose and mouth, and plexiglass shield, where splashes of potentially infectious materials may be generated. Their recommendations are permissive of clinically appropriate laboratory testing, including pretransfusion testing, using barrier isolation precautions. Most individuals with suspected EVD will have a fever of another etiology, such as Plasmodium falciparum malaria. We believe that forgoing all routine pretransfusion laboratory testing may result in a greater increase in poor clinical outcomes than any diminution in the risks to laboratory personnel will justify. It is imperative for all laboratory directors, working with institutional infection control and safety personnel, to evaluate their hospital policies for potentially infectious patients and provide a safe environment for their patients and employees.     

Polyethylene glycol versus low-ionic-strength solution in pretransfusion testing: a blinded comparison study

BACKGROUND: Polyethylene glycol (PEG) has been shown to potentiate antigen-antibody reactions. STUDY DESIGN AND METHODS: To investigate the utility of PEG in pretransfusion testing, a blinded comparison study of PEG and a low-ionic-strength additive solution (LISS) was conducted. A total of 500 patient samples were tested in parallel with reagent antibody-detection cells using blind-coded PEG and LISS potentiators. RESULTS: In 34 (34%) of 100 samples with known antibodies in the Rh, Kell, Duffy, Kidd, and MNS systems, PEG antiglobulin reactions were stronger (total score, 382) than LISS antiglobulin reactions (total score, 216), and in 66 cases (66%), they were equal to those of LISS. Of 400 samples without detectable antibodies, 384 were negative with PEG and LISS, and 16 were positive in PEG tests and negative in LISS. Seven of the 16 were clinically important antibodies (D, 1; E, 3; Fya, 1; Jka; 1; Jkb, 1), and four were clinically benign antibodies (Le(a), 2; McCc, 1; Sda, 1). Five of the 16 demonstrated inconclusive PEG reactions, for a false-positive rate of 5 in 400 (1.3%). Of the 500 samples, none was negative in PEG tests and positive in LISS (0% false-negative rate). CONCLUSION: Although PEG demonstrates a relatively high false-positive rate, PEG is more sensitive than LISS in detecting clinically significant antibodies.     

Advances in pretransfusion infectious disease testing: ensuring the safety of transfusion therapy

The public expects a zero-tolerance policy for the transmission of infectious agents by blood transfusion. Although unrealistic, the efforts to reach this goal have produced an extremely safe albeit costly blood supply [82]. Blood collecting agencies, the FDA, physicians, and scientists have over the past 20 years created a complex system of layers of protection to interdict transfusion-transmitted infections (Fig. 2). As new, exotic, potentially blood transmittable infectious agents evolve [83], new barriers will be erected to [figure: see text] interdict these agents. In the interim, the US blood supply is the safest in the world.     

The evolution of pretransfusion testing: from agglutination to solid-phase red cell adherence tests

Hospital transfusion services and blood centers still use manual hemagglutination tests for most of their serological procedures. Automation of hemagglutination reactions has proven to be difficult, primarily because hemagglutination lacks an objective endpoint which can be easily interpreted by inexpensive instruments. Alternatively, solid-phase red cell adherence assays for ABO cell and serum grouping, Rh typing, red cell and platelet antibody screening, red cell and platelet crossmatching, IgA deficiency screening, hepatitis B surface antigen, and HIV antibody screening have been developed. The performance of these assays compares favorably with current hemagglutination and enzyme immunoassay methods. All of these tests share a common objective endpoint of adherence or nonadherence of indicator red cells. This uniformity allows easy interpretation of results visually, spectrophotometrically, or by image analysis. The latter technique has the potential to revolutionize the reading and interpretation of all agglutination tests. Solid-phase red cell adherence tests in microplates are ideal for batch processing large numbers of specimens. However, adherence tests are not restricted to this format. Therefore, blood grouping dipsticks have been produced, which permit testing of individual blood samples even outside of the laboratory.     

The evaluation of a positive direct antiglobulin test (autocontrol) in pretransfusion testing revisited

Direct antiglobulin tests (DATs) using anti-IgG were performed on 65,049 blood samples from prospective transfusion recipients; 3570 tests (5.49%) were positive. Using criteria published previously (primarily excluding patients not transfused within the preceding 14 days), 778 samples from other than neonatal patients were selected for further evaluation. Eluates that did not react were obtained on 518 (66.6%) of these samples. Warm-reactive autoantibodies were apparent in 192 eluates, while 16 contained drug-related antibodies, anti-A or anti-B from prior transfusion with ABO mismatched blood components, or anti-D passively acquired from immune serum globulin. Fifty-two eluates contained alloantibodies; however, in only six of these cases did the corresponding serum lack unexpected alloantibodies, as determined by routine pretransfusion studies. Three additional weakly reactive clinically significant alloantibodies were detected solely through additional serum tests performed on DAT-positive samples. On the basis of these findings, the DAT had a low predictive value when used to detect the early manifestations of an immune response to recently transfused red cells. Elimination of the autocontrol from routine pretransfusion testing, therefore, carries minimal risk to patients yet will undoubtedly contribute to the containment of health care costs. Moreover, the risk is lower than that associated with the elimination of the antiglobulin crossmatch.     

How do we use molecular red blood cell antigen typing to supplement pretransfusion testing?

The molecular basis of many blood group antigens is known, and it provides a means for predicting the red blood cell phenotype. Molecular typing methods are useful when serologic typing cannot be performed, due to sample or reagent limitations. We discuss the implementation of a commercial molecular typing assay at our Transfusion Service, the indications for testing, and the advantages and drawbacks of the assay. We also present our algorithm for selecting candidates for testing.     

Comparison of a manual hexadimethrine bromide-antiglobulin test with saline- and albumin-antiglobulin tests for pretransfusion testing

A prospective double-blind study compared a manual hexadimethrine bromide (Polybrene) antiglobulin antibody detection test (P-AHG) and crossmatch with the albumin-antiglobulin antibody detection test and saline-antiglobulin crossmatch routinely used in our laboratory. A total of 10,084 pretransfusion blood samples from approximately 6000 patients were tested. The P-AHG method detected 153 of 157 alloantibodies for which antigen-negative, crossmatch-compatible blood is routinely provided. All four antibodies not detected were anti-K. The routine techniques detected 147 of the 157 alloantibodies. The P-AHG method detected only 36 percent of the alloantibodies for which crossmatch-compatible blood is routinely provided without determination of the antigen status of the donor unit's red cells (e.g., anti-Lea), whereas the routine method detected 91 percent of such antibodies. Eighty-six percent of the 189 alloantibodies detected by the Polybrene technique were found before the addition of antiglobulin. The manual Polybrene test is a rapid and sensitive technique; it may be used without an antiglobulin phase as a routine crossmatch procedure when accompanied by a sensitive antibody detection test that includes antiglobulin and an additional test to ensure ABO compatibility.