The direct antiglobulin test (DAT; sometimes referred to as the "Coombs" test) continues to be one of the most widely used assays in laboratory medicine. First described about 70 years ago, it is ...elegantly simple in design, yet it is widely complex in its applications and interpretations, and it is prone to false-positive and false-negative results. The overall objective of our review is to provide practicing pathologists with a guide to identify situations when the DAT is useful and to highlight disease-specific shortcomings as well as general pitfalls of the test. To accomplish these goals, this review will discuss the following: (1) the history of the DAT, (2) how the test is performed in the clinical laboratory, (3) clinical situations for its use, (4) its interpretation, and (5) the pitfalls associated with DAT assays, including causes of false positivity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
The ideal way to screen for the presence of alloantibodies is by antibody screening panels which represent all clinically significant antigens in appropriate dosage. Most centers use pooled O-cells ...for antibody screening as it has antigens of non-ABO blood group systems that are prevalent in a representative population. Pooled O-cells sometimes fail to detect antibodies to less prevalent red blood cell antigens with reduced expression or show a dosage phenomenon. Despite pooling 4 to 5, O-donor segments, sometimes, it is difficult to detect clinically significant antibodies. False-negative indirect Coombs test by pooled O-cells may delay getting a compatible unit for elective cases where type and screen policy is used. Donor units with weak antigenic expression or units showing dosage can come compatible despite being antigen positive and lead to a hemolytic reaction. We report two cases where antibody screening by pooled O-cells was negative; still, cross-match was incompatible. Antibody screening with a three-cell panel was positive. Antibody identification with 11-cell panels confirmed the alloantibody to be anti-E. The present cases emphasize the importance of three-cell panels over pooled O-cells.
Summary
Red blood cell autoimmunity and alloimmunity are potentially linked. Quantification of this association can tailor extensively matched red blood cell transfusions in patients with ...autoimmunity. Using an incident new‐user cohort comprising 47 285 previously non‐transfused, non‐alloimmunised patients, we compared transfusion‐induced red blood cell alloimmunisation incidences in direct antiglobulin test (DAT)‐positive and control patients. Additionally, we performed case–control analyses to handle potential confounding by clinical immunomodulators. Among (IgG and/or C3d) DAT‐positive patients (N = 380), cumulative red blood cell alloimmunisation incidences after 10 units transfused reached 4.5% (95% confidence interval CI 2.5–8.2) versus 4.2% (CI 3.9–4.5, p = 0.88) in controls. In case–control analyses, alloimmunisation relative risks among DAT‐positive patients increased to 1.7 (CI 1.1–2.8). Additional adjustments for pre‐DAT transfusion exposure or the extent of Rh/K mismatching did not impact results. In conclusion, while patients with DAT positivity show an intrinsically increased alloimmune red blood cell response, their absolute risk is comparable to control patients due to counteracting co‐existing immunosuppressive conditions. Consequently, isolated DAT positivity in patients lacking overt haemolysis or complicated alloantibody testing does not seem to warrant extended matching strategies.
Autoimmune hemolytic anemias (AIHAs) are rare and heterogeneous disorders characterized by the destruction of red blood cells through warm or cold antibodies. There is currently no licensed treatment ...for AIHA. Due to the paucity of clinical trials, recommendations on diagnosis and therapy have often been based on expert opinions and some national guidelines. Here we report the recommendations of the First International Consensus Group, who met with the aim to review currently available data and to provide standardized diagnostic criteria and therapeutic approaches as well as an overview of novel therapies. Exact diagnostic workup is important because symptoms, course of disease, and therapeutic management relate to the type of antibody involved. Monospecific direct antiglobulin test is considered mandatory in the diagnostic workup, and any causes of secondary AIHA have to be diagnosed. Corticosteroids remain first-line therapy for warm-AIHA, while the addition of rituximab should be considered early in severe cases and if no prompt response to steroids is achieved. Rituximab with or without bendamustine should be used in the first line for patients with cold agglutinin disease requiring therapy. We identified a need to establish an international AIHA network. Future recommendations should be based on prospective clinical trials whenever possible.
Background
Accurate antibody titration is crucial in prenatal evaluations to identify patients who need clinical monitoring for hemolytic disease of the fetus and newborn (HDFN) causing fetal anemia. ...This study compares the established gold standard method of manual tube saline indirect antiglobulin testing (SIAT) with the newer automated solid phase (ASP) method of antibody titration and aims to establish the critical titer threshold for ASP that corresponds to the previously established SIAT critical threshold of ≥16 used in our laboratory.
Study Design and Methods
One hundred fifty‐seven prenatal and donor plasma samples with known antibodies were tested using both SIAT and ASP methodologies and results were compared.
Results
The study found that ASP titers were, on average, 1.33 dilutions higher than SIAT titers. The critical titer cutoff for ASP was determined to be ≥32, which is one tube higher than the SIAT cutoff of ≥16.
Discussion
The ASP method for antibody titration offers greater reproducibility and efficiency compared with manual SIAT titration. This study suggests that a titer cutoff of ≥32 is appropriate for most clinically significant antibodies using ASP. However, further research is needed to determine the comparability of ASP with SIAT in samples with multiple antibodies, anti‐M antibodies, and other less common antibodies. Validation of the ASP titer cutoff against HDFN clinical outcomes is required before implementing this test for routine use in perinatal antibody titration.
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