An indirect Coombs test is performed to predict whether the fetus is at risk for
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Antibodies are a part of your immune system. They fight germs, but sometimes they make a mistake and target your body's healthy cells instead. The Coombs test checks your
blood for antibodies that attack red blood cells. You might also hear it called an antiglobulin test or red blood cell antibody screening. Not everyone's red blood cells are alike. Your
immune system will make antibodies if it finds ones that don't match yours. They're keyed to specific areas on the outside of the cell. Some of these antibodies are related to your blood type. There are two types of Coombs tests. The direct test looks for
antibodies that are stuck to red blood cells. The indirect test looks for antibodies floating in the liquid part of your blood, called serum. Doctors use the indirect Coombs test, also called IAT, to prevent problems. They'll check your blood before you get a transfusion to make sure it doesn't have antibodies that would react badly to the donated blood. It's part of the "type and screen"
process. Pregnant women get a prenatal antibody screening with an indirect Coombs test. It checks the mother's blood to see if there are antibodies that could pass to and harm their unborn baby. A direct Coombs test, or DAT, may help explain why you're not feeling great or have symptoms that suggest trouble related to your blood. You might get sick after a blood transfusion if the donor's blood wasn't a good match. Your body may recognize those other blood cells as foreign and make antibodies to get rid of them, even though they're meant to help. A
blood disease called autoimmune hemolytic anemia happens when antibodies destroy your own red blood cells faster than your body can make them. You can get it because of: Babies with yellowish
skin and eyes may have hemolytic disease of the newborn (HDN). Some antibodies from their mother could be attacking
their red blood cells. This happens most often when the part of the baby's blood type inherited from the father doesn't mix well with the mother's. A technician uses a needle to take a small sample of blood from a vein in your hand or arm. You may feel a small skin prick and have a little
bleeding or bruising where the needle goes in. Then they'll send your blood to a lab. Both the direct and indirect tests can look for simply the presence of antibodies in general or for a specific antibody. Before a blood transfusion, each package of donated blood also needs to be tested. Cross-matching is a special kind of IAT that may be done before a blood transfusion. The lab mixes your serum (where the antibodies are) with red blood cells from
the donor. A negative indirect Coombs test is good news. It usually means you don't have antibodies in your serum, so you: A positive result before a blood
transfusion is a warning that the doctor will have to be careful when choosing donor blood. People who need a lot of blood transfusions may develop a lot of different antibodies and have a harder time finding blood that will work. A positive indirect Coombs test during pregnancy means you may need to take steps to protect your baby. Not all antibodies the test finds are
harmful, so depending on what the test was looking for, you may need more tests to narrow down which ones you have so your doctor will know what to do next. A positive direct Coombs test shows you have antibodies attached to your red blood cells, but it doesn't necessarily tell you which ones or why. Regardless of the result of a direct Coombs test, you may need other tests to find the right diagnosis
and treatment. A. Wesley Burks MD, in Middleton's Allergy: Principles and Practice, 2020 The type II immune reactions involve IgG, IgM, and to a lesser extent IgA,
which are directed to cell-surface antigens on erythrocytes, neutrophils, platelets, and epithelial cells of glandular or mucosal surfaces or to antigens on tissues (e.g., basement membranes). The sensitizing antigens in these cases can be natural cell surface antigens, modified cell surface antigens, or haptens attached to cell surfaces. Three distinct immune reactions might be induced: The first occurs by opsonization, which is facilitated by complement activation; the second induces
complement-mediated lysis; and the third is antibody-dependent cell-mediated cytotoxicity or ADCC. These mechanisms afford protection against infections and eradication of malignant cells but can also result in damage to various tissues associated with responses to self-antigens. An example of opsonization is phagocytic cell destruction of antibody-coated platelets, causing immune thrombocytopenia. The second category is demonstrated by penicillin binding to the surfaces of erythrocytes,
creating a nonself-antigen composed of penicillin-modified erythrocyte cell surfaces. Antipenicilloyl antibodies, initially IgM and later IgG, fix to erythrocyte surfaces and concomitantly activate complement, leading to the lysis of the cell with penetration of the terminal hydrophobic complement membrane attack complex (MAC, C5 to C9). Clinically, this condition is known as penicillin-induced autoimmune hemolytic anemia. Other clinical examples of this reaction include quinidine-induced
autoimmune thrombocytopenia and ceftriaxone-induced autoimmune hemolytic anemia.39 ADCC is the process by which NK cells and other cells recognize IgG bound to target cells, such as neoplastic cells, and triggers the release of cytotoxic granules. Immunological Methods in MicrobiologySukhadeo B. Barbuddhe, ... Deepak B. Rawool, in Methods in Microbiology, 2020 9.1.4 Coombs testCoombs test, also known as anti-globulin test, detects the antibodies that may agglutinate to the red blood cells and cause haemolysis (Ducrotoy et al., 2016). Normally, no direct agglutination takes place with red cells coated with IgG or complement and red cells are said to be sensitized with complement or IgG. For an agglutination to occur, an additional antibody that reacts with the Fc portion of the IgG or with the C3b or C3d component of the complement must be added to the system forming a bridge between the antibodies or complement coated red cells resulting in agglutination (Beh, 1973; Beh & Lascelles, 1973; Cunningham et al., 1967). A direct Coombs test is observed when antibodies are located on the red cells and haemolysis is mediated through the host immune system. IgG-ELISA and Coombs test are reported to have good correlation; nonetheless, the ELISA and Coombs test remain positive more than other agglutination assays. Coombs test titre will remain high with chronic long-term Brucella infection, even before the diagnosis is made. In acute brucellosis, the Coombs titre remains 4–16 times higher than the STAT titres; whereas, the titres are 16–256 times higher in chronic patients without treatment (Ducrotoy et al., 2016). Read full chapter URL: https://www.sciencedirect.com/science/article/pii/S058095171930025X CCynthia C. Chernecky PhD, RN, CNS, AOCN, FAAN, in Laboratory Tests and Diagnostic Procedures , 2013 Coombs' Test, Direct IgG—SerumNorm.Negative. Positive.Anemia (hemolytic, drug induced), autoimmune hepatitis, erythroblastosis fetalis, leukemia (chronic lymphocytic), and transfusion reaction. Drugs include (possibly as a result of IgG erythrocyte sensitization by the drugs) aminopyrine, cephalosporins, chlorpromazine, dipyrone, ethosuximide, hydralazine, hydrochloride, insulin, isoniazid, levodopa, mefenamic acid, melphalan, methyldopa, methyldopate hydrochloride, oxyphenisatin,p-aminosalicylic acid, penicillins, phenacetin, phenytoin, phenytoin sodium, procainamide hydrochloride, quinidine gluconate, quinidine polygalacturonate, quinidine sulfate, rifampin, streptomycin sulfate, sulfonamides, and tetracyclines. Description.SeeCoombs' test, Direct—Serum. This test is more specific than a direct Coombs' test and is performed after a positive direct Coombs' test. The direct Coombs' IgG test mixes Coombs' antiglobulin containing only anti-IgG with the client's washed red blood cells and observes for agglutination, which signals the presence of IgG on the surface of the client's erythrocytes. Professional ConsiderationsConsent form NOT required. PreparationProcedure1. Draw a 5-mL blood sample. Postprocedure Care1. Write recent transfusions and drugs on the laboratory requisition. Client and Family Teaching1. Results are normally available within 24 hours. Factors That Affect Results1. Cold agglutinins may cause false-positive results. 2.False-negative results may occur in the presence of sensitized erythrocytes with less than 100-300 IgG molecules per cell. Other Data1. The test must be completed within 24 hours of specimen collection. Immunological Methods in MicrobiologyTony A. Slieman, Joerg Leheste, in Methods in Microbiology, 2020 4.1.1.3.3 Coombs testThe Coombs test, named after the British Immunologist Robin R. Coombs, together with his colleagues, first described it in 1945 (Coombs, Mourant, & Race, 1945). There are two types of Coombs test, the direct and indirect antiglobulin test (DAT, IAT). Both utilize rabbit anti-human globulin that is also referred to as Coombs reagent. Common uses of this test include suspicion of autoimmune hemolytic anaemia, prenatal compatibility testing, and cross-typing for blood transfusions. The direct Coombs test assesses antibodies adherent to the patient's own RBCs, while the indirect test measures free serum antibodies against RBCs of a fetus during pregnancy or recipient of a blood transfusion. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/S0580951720300015 Anemia and PregnancyRobert Resnik MD, in Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice, 2019 Normocytic AnemiaBecause of the diverse nature of normocytic anemia, it is the most difficult type to evaluate. The reticulocyte count varies according to whether RBC production is increased, normal, or decreased. If erythropoiesis is increased, one must differentiate between hemorrhage and an increased rate of destruction. The blood smear may reveal a type of RBC shape that can be virtually diagnostic. Schistocytes are seen in microangiopathic hemolysis—as in the HELLP syndrome (hemolysis,elevatedliver enzymes,lowplatelets) and thrombotic thrombocytopenic purpura—and in association with prosthetic heart valves. Other types of poikilocytes that may be encountered on peripheral blood smear examination and that may suggest an etiology include sickle cells, target cells, stomatocytes, ovalocytes, spherocytes, elliptocytes, and acanthocytes. The Coombs test differentiates immune from nonimmune causes of hemolysis. Immune hemolysis is related to alloantibodies, drug-induced antibodies, and autoantibodies. Nonimmune causes of hemolysis include various hereditary disorders such as hemoglobinopathies, disorders of the RBC membrane (hereditary spherocytosis and hereditary elliptocytosis), deficiency of an RBC enzyme, or the porphyrias, and acquired, nonimmune hemolytic anemias may be caused by PNH or lead poisoning. Bone marrow examination can be helpful for evaluation of patients who have hypoproliferative anemias with normal iron studies, and folate and vitamin B12 levels. If increased ring sideroblasts are identified, both acquired and hereditary forms of sideroblastic anemia must be considered. If erythropoiesis is normoblastic, etiologic mechanisms fall into two major categories. The first category has myeloid-to-erythroid production ratios greater than 4 : 1 and includes red cell aplasia, primary marrow-based disorder (e.g., chronic myeloid leukemia), effects of chronic diseases, infection (e.g. parvovirus), and endocrine disorders such as hypothyroidism and hypopituitarism. In contrast, the myeloid-to-erythroid ratio is decreased (e.g., 2 : 1 or less) when erythroid hyperplasia is present, as with relatively acute hemolysis or myelodysplastic syndrome (MDS) if in conjunction with significant dysplasia. If there is megaloblastic erythropoiesis and erythroid hyperplasia, considerations include nutritional deficiencies such as folate and vitamin B12 deficiencies, MDS, drugs, particularly those that interfere with nucleotide synthesis, and toxins (benzene, arsenic). SpleenAttilio Orazi, Magdalena Czader, in Differential Diagnosis in Surgical Pathology (Second Edition), 2010 Differential Diagnosis• History and Coombs test critical for all differential diagnoses ▪ITP •Patients have thrombocytopenia but are usually not anemic •The coexistence of ITP and hemolytic anemia is called Evans syndrome •Antiplatelet antibodies are present in plasma and on patient's platelets •Histologically, “dirty cords” are due to phagocytosis of platelets (best seen in touch preparations), but there is no evident erythrophagocytosis ▪Congestive splenomegaly •Patients have portal hypertension and usually have liver disease •Spleen shows an increased stroma content (fibrocongestive splenomegaly) •Coombs test negative ▪Hereditary spherocytosis •Family history •Lifelong hemolytic anemia •Abnormal red blood cell morphology •Coombs test negative Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781416045809000150 Erythrocyte DisordersDouglas J. Weiss, Harold Tvedten, in Small Animal Clinical Diagnosis by Laboratory Methods (Fifth Edition), 2012 Direct Coombs TestThe direct Coombs test identifies the presence of antibodies or complement on RBCs. The antibodies and complement on an RBC may or may not be directed toward the RBC itself and may or may not damage the RBC. The screening test is a “polyvalent direct antiglobulin test” in which a polyvalent Coombs reagent is mixed with the patient's RBCs. This reagent contains species-specific antibodies against various classes of antibodies and complement. If the patient's RBCs have enough antibody or complement to be detected and the ratio of these antibodies to the antiglobulin is in the proper proportion, gross or microscopic hemagglutination occurs (i.e., a positive reaction). Some laboratories use monovalent antiglobulin to classify IMHA as either immunoglobulin M (IgM) or immunoglobulin G (IgG) types and detect the presence of complement on RBCs. The pattern found in 48 dogs at the University of Minnesota was: 71% IgG positive, 10% IgG and IgM positive, and 19% IgG, IgM, and complement positive. The effect of steroid treatment in vivo is unpredictable. Dogs remain Coombs-positive for variable lengths of time during corticosteroid treatment of IMHA. The direct Coombs test is neither highly specific nor sensitive for IMHA. The test is positive in only 60% to 70% of canine IMHA cases. Possible reasons for false-negative results include insufficient quantity of antibody on RBCs, temperature at which the test was performed, improper antigen : antibody ratio, and elution of low-avidity antibodies from RBCs during washing. To ensure that the proper antigen : antibody ratio is achieved, serial dilutions of the antiglobulin reagent should be routinely used. Over time, antibody and complement elute off the RBCs in blood samples. The time that an EDTA blood sample may be stored before a Coombs test is unknown. Therefore results obtained from samples sent to laboratories by mail are questionable. Alsever's solution is good for storing antibody-coated RBCs but is not readily available to most veterinarians. Positive Coombs reactions are expected in RBC parasite infections, incompatible blood transfusions, and drug reactions, which cause RBCs to appear foreign to the immune system. The specificity of the Coombs test for IMHA is often considered good, but positive reactions frequently occur in the absence of evidence of IMHA. These false positives are not detected as often as false-negative results, because a Coombs test is usually not requested unless the patient has signs of IMHA. Of Coombs-positive anemias in 134 dogs, half were positive for the third component of complement (C3), but there was infrequent evidence of intravascular or extravascular hemolytic anemia.21 Therefore a positive Coombs test should be supported by other strong evidence of IMHA. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B978143770657400003X Liver Failure, Anemia, and Blood TransfusionThomas J. Divers, in Equine Emergencies (Fourth Edition), 2014 Diagnosis• Use Coombs test with whole blood (EDTA) to help confirm an immune reaction. Note: Close examination of the sample may reveal autoagglutination (presence of clumps), in which case a Coombs test is not needed for confirmation. •Liver function is frequently affected and not always correlated with severity of NI. •Some cases, mostly those with one or more transfusions, may have progressive liver failure, possibly associate with iron overload, even after recovering from the hemolytic aspect of NI. What to DoNeonatal Isoerythrolysis•If the foal is less than 48 hours old, do not allow it to nurse unless the mare's colostrum/milk has a Brix refractometry score of <15%. If the foal needs to be refrained from nursing, this should be done with as little stress as possible to the foal; use a muzzle and if practical, do not physically separate the two. Continue to milk the mare. •For peracute severe cases with PCV <20% within 24 hours, do the following: •For horse foals, perform a transfusion. A crossmatch (major and minor) is ideal. •If a crossmatch is not feasible, using an Aa/Qa-negative donor usually is safe and effective. •The mare's blood may be used if it is washed 3 times and suspended in saline solution before each transfusion, although it is time consuming. •Lastly, using a gelding of the same breed that has never received a transfusion is often successful. •Note: If an oxyglobin product becomes available in the market, its ideal use would be in peracute cases of hemolytic anemia while whole-blood transfusion is being organized. •Mule foals: Use a horse gelding or a female donor that has not been previously bred with a donkey. •All equine practices should ideally have Aa/Qa-negative donors identified for emergency purposes. Blood typing can be performed by sending samples of acid-citrate-dextrose (ACD) anticoagulated blood to: •Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis, CA 95616 (916-752-2211) •Equine Blood Typing Research Laboratory, University of Kentucky, Department of Veterinary Science, Lexington, KY 40546 (606-257-3022) •Donors should ideally be free of Aa and/or Qa antigens and hemolytic and agglutinating Aa, Qa antibodies, but these are hard to find. •Administer intravenous fluids at maintenance level (approximately 60 mL/kg per day). •Important: Administration of needed intravenous fluids decreases PCV but does not reduce the total numbers of RBCs and would be expected to improve oxygen delivery as long as viscosity is sufficient to maintain capillary pressure. •Administer dexamethasone, 0.04 mg/lb (0.08 mg/kg IV), only in peracute cases (foals 2 days of age or younger with PCV <12%) if donor cells cannot be administered immediately or if compatibility is uncertain. •Administer intranasal oxygen (5 to 10 L/min) bubbled through a nasopharyngeal tube if the foal is severely anemic. This will increase free oxygen in the plasma. •Administer antibiotics to all foals with NI to minimize sepsis. Despite evidence of passive transfer of colostral antibodies, foals with NI can become septic. One reason for this is that the transfusion may cause immunosuppression. Also, some confirmed foals with NI have partial failure of passive antibody. Valuable foals should be administered a combination of intravenous penicillin and amikacin (if renal function is normal) or ceftiofur; less monetarily valued foals can be given a combination of trimethoprim-sulfamethoxazole, 20 mg/kg PO q12h, and penicillin 22,000 IU/kg IM q12h. •Administer antiulcer medication: sucralfate, 1 g PO q6h, with or without a histamine-2 receptor blocker or proton pump blocker. Due to hypoxia and stress, the foals may be predisposed to gastric ulcers. •Provide nutritional support (Land-O-Lakes) foal milk replacement, mare's milk, or goat's milk, at 15% to 20% of body weight per day during the time the foal is not allowed to nurse. •Provide supportive care, such as keeping the foal warm but not hot. •Expect a second decline in PCV 4 to 11 days after the transfusion. What Not to DoNeonatal Isoerythrolysis•Do not let a newborn foal nurse the mare's colostrum if the mare has ever had a whole blood transfusion. •The foal should be 36 to 48 hours old before it is allowed to nurse a mare that has received a transfusion. An alternate source of colostrum should be provided and the foals IgG checked at 12 to 18 hours. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781455708925000209 Autoimmune and Intravascular Hemolytic AnemiasRobert S. Schwartz, in Goldman's Cecil Medicine (Twenty Fourth Edition), 2012 The Antiglobulin (Coombs) TestThe antiglobulin test is central to the diagnosis of autoimmune hemolytic anemia and to an understanding of the antibody-mediated mechanism of red blood cell destruction in this disorder (Fig. 163-1B to D). The terms complete and incomplete antibodies refer to the ability (or inability) of antibodies to cross-link adjacent red cells, thereby building the lattice needed for the macroscopic clumping of red cells. The strong negative charge of red blood cells suspended in saline keeps them apart, even if they have a coating of antibodies—the average distance between cells is 24 nm. IgM antibodies, being pentamers, are efficient agglutinins; with five antigen-binding sites, they can bridge this distance. In contrast, bivalent IgG antibodies usually cannot cause the clumping of saline-suspended erythrocytes. The test that reveals antibody-coated red blood cells is the direct Coombs (antiglobulin) test. The indirect Coombs test was devised to seek the presence of incomplete antibodies in the patient's serum. As presently used, the standard antiglobulin reagent contains antibodies against all four classes of IgG and components of complement (usually C3 and C4). A positive Coombs test requires cautious interpretation when there are no other features of autoimmune hemolytic anemia. False-positive test results are not unusual. The reported incidence of positive antiglobulin tests in normal blood donors and general populations of hospitalized patients varies widely—from 1 in 100 to 1 in 15,000. Differences in the technique used to perform the test account for this variation. The usual reason for a false-positive direct antiglobulin test is nonspecific, low-avidity adherence of IgG to red cells. In rare cases, however, the result is not a false-positive but a harbinger of the development of autoimmune hemolytic anemia. False-negative direct antiglobulin tests are usually due to low-affinity autoantibodies that spontaneously elute from the red cell in vitro or to amounts of erythrocyte-coating antibodies that are below the limit of detection by the antiglobulin test. The distinction between a true-positive and a false-positive direct antiglobulin test can be made by eluting the antibody from the red cells and testing its ability to bind to normal red cells. In a false-positive reaction, the eluted antibody does not bind to normal red cells, whereas binding does occur in a true-positive test.
TreatmentThere are no controlled trials of the treatment of autoimmune hemolytic anemia. A corticosteroid, usually prednisone, is the standard initial treatment. Splenectomy is indicated in patients who fail to attain or sustain a remission. If splenectomy does not result in improvement, one or more immunosuppressive agents can be tried. The physician should not withhold red cell transfusions from symptomatic patients. Initial TherapyCorticosteroidsIn the initial management of the disease, the standard of practice is to administer prednisone at a dose of 1.0 to 1.5 mg/kg/day. The duration of treatment at this dose is an unsettled question, but a response—manifested by a rise in the hematocrit and a fall in the reticulocyte count—is usually evident within 3 to 4 weeks. A patient who fails to improve within this time is unlikely to respond to further treatment with prednisone. In a patient who does respond, slow reduction of the dose of prednisone is essential to avoid a relapse. The usual tapering schedule is a weekly reduction of the initial dose by 10 mg/day to a dose of 30 mg/day, followed by a weekly reduction of 5 mg/day to 15 mg/day. Thereafter, slow, cautious tapering over at least 4 months is the rule. A rise in the reticulocyte count or a fall in the hematocrit should prompt an increase in the dose, usually to the previous level. About 25% of patients treated with corticosteroids in this manner enter a stable, complete remission; half of patients require continuous, low-dose prednisone; and the remaining 25% respond only transiently or not at all or are unable to tolerate continuous corticosteroid treatment. There is no reliable evidence that alternate-day maintenance treatment is superior to daily treatment, but some patients tolerate this schedule better than daily prednisone. Very high doses of intravenous methylprednisolone have been advocated for stubborn cases, but such treatment is risky and should be considered experimental. TransfusionRed blood cell transfusions (Chapter 180) are indicated in patients with disabling symptoms of anemia: marked fatigue, reduced exercise tolerance, or an inability to work. These symptoms often develop when the hemoglobin concentration falls below 10 g/dL, but the decision to administer red cell transfusions should not depend primarily on laboratory tests—the patient's clinical status is the dominant factor. Some patients can tolerate a stable hemoglobin level as low as 8 g/dL; however, symptoms of coronary artery disease or heart failure may force the decision to transfuse before the hemoglobin level falls below 10 g/dL. Regardless of the patient's clinical status, rapid transfusion of large volumes of red cells can have serious adverse consequences. The blood should be administered at a rate that does not exceed 1 mL/kg/hour. The risk of reactions to blood transfusions (Chapter 180) in patients with autoimmune hemolytic anemia is always present because of the destruction of transfused blood by the patient's autoantibodies. This hazard is increased if the patient also has alloantibodies that were induced by pregnancy or previous transfusions. For these reasons, the blood bank should be alerted to the diagnosis and should be informed if the patient was ever pregnant or has ever had transfusions. It is important for the managing physician to understand that no patient with symptomatic autoimmune hemolytic anemia should be denied blood transfusions because of an “incompatible crossmatch.” The patient's positive antiglobulin test always interferes with compatibility testing. Communication and cooperation between the patient's physician and specialists in transfusion medicine (Chapter 180) are essential in reducing the risks associated with transfusion in patients with autoimmune hemolytic anemia. SplenectomyBecause the spleen is the major site of red cell destruction in autoimmune hemolytic anemia, splenectomy should be considered for patients who have not responded to corticosteroids or who have maintained a stable but corticosteroid-dependent remission. A complete, durable remission follows splenectomy in one half to two thirds of cases. Attempts to predict responsiveness to splenectomy by measuring the splenic sequestration of 51Cr-labeled erythrocytes have not been reliable. The only way of determining the effectiveness of splenectomy in a given patient is to perform the procedure. Laparoscopic splenectomy, a safe method of removing the organ, is now the preferred surgical technique. A major risk is post-splenectomy sepsis secondary to encapsulated bacteria, particularly pneumococci and especially in children. Splenectomy also increases susceptibility to babesiosis, ehrlichiosis, and malaria. Preoperative immunization with polyvalent pneumococcal and Haemophilus influenzae vaccines reduces the risk of post-splenectomy sepsis. In children, a prophylactic antibiotic, generally penicillin or amoxicillin, is essential after splenectomy. Evidence for the effectiveness of (or need for) prophylactic antibiotics in splenectomized adults is inconclusive. Education of the patient concerning the risk for serious infection after splenectomy is also important. A rise in the platelet count occurs in almost all patients after splenectomy. The increase rarely exceeds 500,000/mL and usually subsides within 3 to 5 months. The low risk for thromboembolism related to post-splenectomy thrombocytosis argues against the need for routine antithrombotic prophylaxis. Therapy in Refractory PatientsRituximabRituximab is a chimeric monoclonal antibody with a high affinity for the CD20 antigen on the surface of normal and malignant B lymphocytes (Chapter 35). The antibody consists of murine variable region sequences and human constant region sequences. The usual dose is 375 mg/m2 by intravenous infusion once a week for four or eight doses, but it may be continued weekly or biweekly if necessary. Rituximab rapidly depletes the circulation and lymphoid tissue of B cells; it can cause allergic reactions and increase the risk for infection. Other Monoclonal AntibodiesMonoclonal antibodies against components of the immune system or cytokines have been used in the treatment of autoimmune hemolytic anemia, but most of the literature on this topic consists of small, uncontrolled series. Among the monoclonal antibodies that have been used are alemtuzumab (anti-CD52, a T-cell marker) and natalizumab (α4 integrin). These and similar monoclonal antibodies should be reserved for experimental use in refractory, transfusion-dependent cases. Immunosuppressive Drugs and Other ModalitiesImmunosuppressive drugs other than corticosteroids can be useful in stubborn cases of autoimmune hemolytic anemia, but no head-to-head trials have compared the efficacy of these drugs. The choice usually depends on safety and familiarity with the agent. Azathioprine has the least toxicity; cyclosporine is nephrotoxic; and cyclophosphamide damages the bone marrow, ovaries, and bladder and impairs spermatogenesis. Mycophenolate has also been tried, with some success in refractory cases. In general, these drugs should be administered only by specialists and should be reserved for patients who have failed to respond to splenectomy or who, because of comorbidities, are not suitable candidates for splenectomy. A variety of other treatments have been used in refractory cases of autoimmune hemolytic anemia, including plasma exchange, vinca alkaloids, danazol (a synthetic androgen), and intravenous IgG. None of these forms of therapy is reliably effective, and none of them has been tested for efficacy in a randomized trial. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9781437716047001639 Blood Cell Antigens and AntibodiesFiona A.M. Regan, in Dacie and Lewis Practical Haematology (Twelfth Edition), 2017 Antiglobulin testThe antiglobulin test (Coombs test) was introduced by Coombs and colleagues in 194531 as a method for detecting ‘incomplete’ Rh antibodies (i.e. IgG antibodies capable of sensitising red cells but incapable of causing agglutination of the same cells suspended in saline), as opposed to ‘complete’ IgM antibodies, which do agglutinate saline- suspended red cells. Direct and indirect antiglobulin tests can be carried out. In the direct antiglobulin test (DAT), the patient’s cells, after careful washing, are tested for sensitisation that has occurred in vivo; in the indirect antiglobulin test (IAT), normal red cells are incubated with a serum suspected of containing an antibody and subsequently tested, after washing, for in vitro-bound antibody. The antiglobulin test is probably the most important test in the serologist’s repertoire. The DAT is used to demonstrate in vivo attachment of antibodies to red cells, as in autoimmune haemolytic anaemia (see p. 255), alloimmune HDN (see p. 491) and alloimmune haemolysis following an incompatible transfusion (see p. 488). The IAT has wide application in blood transfusion serology, including antibody screening and identification and crossmatching. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780702066962000217 Why is indirect Coombs test done in pregnancy?An indirect Coombs test is given to every pregnant person to see if they have antibodies against Rh-positive blood. For example, if you have an Rh-negative blood type (such as O-, A-, B- or AB-), your red blood cells don't have the Rh factor marker on them.
What is indirect Coombs test used for?The indirect Coombs test looks for antibodies that are floating in the blood. These antibodies could act against certain red blood cells. This test is most often done to determine if you may have a reaction to a blood transfusion.
What happens when a baby is Coombs positive?What will happen to my baby if the Coombs test is positive? Your baby will be examined by a doctor or Advanced Nurse Practitioner. Blood tests will be taken to look for jaundice and anaemia. High jaundice levels will be treated with phototherapy.
What Coombs test would confirm hemolytic disease of newborn?The direct Coombs test (see below) confirms the presence of anti-D and hence that the mother has been sensitized. Only a small amount of fetal blood need enter the mother's circulation for sensitization to occur. Typically, this occurs during the delivery of the first-born Rh D-positive child.
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