Red blood cell alloimmunization among recipients of blood transfusion in India: A systematic review and meta-analysis.

BACKGROUND AND OBJECTIVES: There is a varied prevalence of red cell alloimmunization being reported from different parts of India. This study aimed to estimate the overall prevalence of alloimmunization in India by performing a systematic review of the literature and to establish the most suitable antigen-matching strategy to reduce the red blood cell (RBC) alloimmunization rate among transfusion recipients. MATERIALS AND METHODS: A systematic search of all the original articles published in English on RBC alloimmunization among transfusion recipients from India in MEDLINE, SCOPUS, CINAHL and Google Scholar bibliographic databases was conducted. After screening the articles as per inclusion/exclusion criteria, data extraction was done independently by two sets of investigators. Meta-analysis was performed by the binary random-effects model using the restricted maximum likelihood method. RESULTS: A total of 44 studies on RBC alloimmunization, with a cumulative sample size of 309,986 patients, were grouped into hospital-based and multiply-transfused patients, which yielded a prevalence of 0.5 (95% confidence interval; 0.3-0.8) and 4.8 (95% confidence interval; 3.9-5.7) per 100 patients, respectively. As many as 1992 alloantibodies were identified among the 1846 alloimmunized patients. The most common antibody identified was anti-E (127; 31.99%), followed by anti-c (75; 18.89%) in multiply-transfused patients. CONCLUSION: The rate of alloimmunization was 0.5 per 100 patients tested for antibodies and 4.8 per 100 patients receiving transfusion. Considering E- and c-antigen-matched red cells along with ABO and RhD matching may significantly reduce the overall occurrence of alloimmunization among Indian population who are transfusion-dependent.

Molecular basis of RhD-negative phenotype in North Indian blood donor population.

Background & objectives: RHD gene typing is highly complex due to homology with RHCE genes. Molecular polymorphism of the RHCE and RHD genes have been characterized among various populations, but no studies have been undertaken among Indians. This study was undertaken to assess the genetic basis of RHD-negative phenotype in Indian blood donor population. Methods: Sample from a total of 200 phenotypically RhD-negative blood donors were analyzed for presence of RHD gene using polymerase chain reaction (PCR). RHD genotyping was done using three primer sets designed for exons 4 and 10 and one set for identification of pseudo (RHDΨ) gene between introns (int) 3 and 4. Amplified PCR products were analyzed by gel-electrophoresis (XY Loper, Uvitech, Cambridge) and confirmed by nucleotide sequencing (ABI 3730 xl 96 capillary system). Results: No PCR product was found in 195/200 (97.5%) of study samples indicating homozygous gene deletion. Of the 5/200 (2.5%) showing RHD gene polymorphisms, 4/200 (2%) were positive for presence of exon 10 only (RHD-CE-D hybrid). RHDΨ gene was not detected in any of the samples tested. One sample showed presence of all three tested regions and was negative for RHDΨ gene. Interpretation & conclusions: RHD gene deletion was found to be the most common cause of an RHD-negative phenotype while RHDΨ gene was, reported to be present in up to 39 per cent of various ethnic populations, but was not detected. RHD-CE-D hybrid gene (found in 2.5% individuals) is important for predicting the requirement of Rh prophylaxis during the antenatal period.

Title: Effect of multiple maternal red cell alloantibodies on the occurrence and severity of Hemolytic Disease of the Fetus and Newborn.

INTRODUCTION: Antenatal antibody screening in India is focused on the detection of anti-D in RhD-negative mothers. HDFN outcome can also be affected by the presence of antibodies other than anti-D. We planned this study to find the impact of 'anti-D in combination with additional antibodies' on the development and severity of HDFN compared with 'anti-D alone'. METHODS: This is a retrospective study performed at a referral center in northern India from October 2015 to March 2018. Antibody screening was performed on women with complicated obstetric history. Women with anti-D antibody were included in the study and categorized on the basis of presence of additional antibody (anti-D alone or in combination with other antibody). Various clinical, laboratory & interventional parameters were used to define HDFN and severe HDFN. Perinatal outcome was then compared between the two groups. RESULTS: A total of 176 women with anti-D antibody were included in the study. Of these, 136 cases (77.3%) had anti-D alone while at least one additional antibody was present in 40 (22.7 %) cases. Most common additional antibodies were anti-C, anti-E and anti-c. After excluding 46 women for various reasons, 130 women were left for final analysis. Approximately 57% and 78% of cases were affected by severe HDFN amongst women with anti-D alone and in combination, respectively. Relative risk of developing severe HDFN was 1.7 times higher in women with additional antibody. CONCLUSIONS: Patients with combination antibodies were found to have more severe HDFN compared to the ones with anti-D alone.

Molecular characterisation of RhD variants in North Indian blood donor population.

OBJECTIVES: A molecular analysis of serologically RhD variant samples was conducted to find the incidence of various D variants in our blood donor population. BACKGROUND: Determining a blood donor's RhD phenotype and genotype is important as transfusion of units with a weak D or partial D phenotype can result in immunisation of the recipients. METHODS: Samples with discrepant D and weak D phenotypes identified on testing with at least five different monoclonal anti-D antisera were considered serological RhD variant and subjected to molecular testing (Massarray kit, Agena Bioscience, San Diego) for variant RHD gene. RESULTS: A total of 39 samples, including 19 RhD discrepant samples and 20 weak D samples, were identified as serological RhD variant from a total of 4386 samples. Thirteen (13/39) samples carried variants leading to weak D phenotype, and eight samples had variants leading to partial D categories. Seven samples (7) could not be characterised, whereas 11 samples were identified as Rh negative (RHD*01N.01) after molecular testing. Overall incidence of D variants in the study population was 0.48%. RHD*weak D type 1(5, 0.1%) and RHD*DFR1 (5, 1%) were the most common variants identified. CONCLUSIONS: Few samples with weak reaction on serological testing were found to be partial D variant and vice versa. Donor centres should develop a protocol for genotyping of samples with aberrant results on serological testing for assessing the actual RhD status of an individual as results of serological testing may be misleading.

Prevalence of DEL phenotype in D- blood donors in India.

CONCLUSIONS: Unlike weak D and partial D, DEL represents a weakened form of D that cannot be detected by conventional serology and requires use of an adsorption-elution method for its detection; therefore, DEL+ samples might be mistyped as D-. The study was undertaken to determine the prevalence of the DEL phenotype among D- blood donors from northern India. A total of 1003 D- blood donors were tested for weak D and DEL by the indirect antiglobulin test and an adsorption-elution method, respectively. Of the total 21,135 blood donors typed for D, 20,132 (95.3%) were D+ and 1003 (4.7%) gave a negative reaction for D. Of the total 1003 D- samples, 8 (0.8%) were weak D and only 2 (0.2%) were DEL+ by adsorption-elution testing. For samples that typed as D-, the majority of individuals (91.1%) were cde/cde (rr) followed by dCe/dce (r´r) in 4.8 percent, and dCe/dCe (r´r´) in 2.2 percent. Both DEL+ samples were also C+. We conclude that the prevalence of the DEL phenotype as detected by serology in D- north Indian blood donors is 0.2 percent, although it is as high as 2.8 percent in D-C+ individuals. There is an association of DEL with C, which can be used as a cost-effective marker for screening large numbers of D- blood donors for DEL.

Prospective Cohort Study to Assess the Effect of Storage Duration, Leuko-Filtration, and Gamma Irradiation on Cell-Free DNA in Red Cell Components.

INTRODUCTION: Damage to a cell and the loss of integrity of its cell membrane leads to the release of endogenous immunogenic molecules, which together are classified as "damage-associated molecular patterns" (DAMPs). Cell-free DNA (cf-DNA) released from nucleosomes may serve as a proco-agulant cofactor and may be an important mediator of immunomodulatory and proinflammatory effects associated with blood transfusion. OBJECTIVES: To assess the levels of cf-DNA in supernatants of stored red cell components and the effect of leukoreduction and gamma irradiation on the release of cf-DNA during storage. METHODS: This is a prospective cohort study on 99 stored red cell components, randomly divided into three groups - buffy coat (BC)-depleted, leuko-filtered (LP), and irradiated (IR) packed red blood cells. Red cell supernatants were drawn over a period of 21 days at three different time points (day 0, 7, and 21) from the study units. cf-DNA extraction was done and quantified by a bench top fluorometer. Change in cf-DNA content, rate of change (µg/day), and percent change were estimated and compared across different groups. RESULTS: cf-DNA content increased (p = 0.000) with storage duration in the BC (median = 238.66 µg, interquartile range [IQR] = 168.42 on day 21 vs. median = 9.44 µg, IQR = 5.23 on day 0) and IR groups (p = 0.000) (median = 245.55 µg, IQR = 253.88 on day 21 vs. median = 7.07 µg, IQR = 13.58 on day 0), while there was a decreasing trend (p = 0.032) in the LP group (median = 4.55 µg, IQR = 10.73 on day 21 vs. median = 8.66 µg, IQR = 6.56 on day 0). The median rate of change in cf-DNA content (11.13 µg/day) and percent change in cf-DNA content (median = 4,106.16%) was highest in the IR group. CONCLUSIONS: Stored red cell components contain significant amount of cf-DNA. Release of cf-DNA is further aggravated by irradiation while leukoreduction leads to a decrease in cf-DNA content.

Importance of donor history of restless leg syndrome and pica to asses iron deficiency.

Iron deficiency is associated with neuropsychological changes such as restless leg syndrome (RLS), pica, hair loss, etc. Our objective was to assess usefulness of history of RLS and pica in relation with iron stores in blood donors. During medical examination, apart from routine questionnaires specific history of RLS and pica was elicited. Along with hemoglobin markers of iron deficiency such as s. iron, s. ferritin and mean corpuscular volume were analyzed. Out of 400 blood donors 41 had h/o pica/RLS/pagophagia. Positive and negative predictive value of above history is 73.17% and 80.5% respectively. We recommend the use of a screening question for pica and/or RLS in blood donor questionnaire.

Comparative evaluation of gel column agglutination and erythrocyte magnetized technology for red blood cell alloantibody titration.

Antibody titration is traditionally performed using a conventional test tube (CTT) method, which is subjected to interlaboratory variations because of a lack of standardization and reproducibility. The aim of this study is to compare newer methods such as get column technology (GCT) and erythrocyte magnetized technology (EMT) for antibody titration in terms of accuracy and precision. Patient serum samples that contained immunoglobin G (IgG) red blood cell (RBC) alloantibodies of a single specificity for Rh or K anitgens were identified during routine transfusion service testing and stored. Titration and scoring were performed separately by and stored. Titration and scoring were performed separately by different laboratory personnel on CTT, GCT, and EMT. Testing was performed a total of three times on each sample. Results were analyzed for accuracy and precision. A total of 50 samples were tested. Only 20 percent of samples tested with GCT shoed titers identical to CTT, whereas 48 percent of samples tested with EMT showed titers identical to CTT. Overall, the mean of th titer difference from CTT was higher using GCT (+0.31) compared with that using EMT (+0.13). Precision shown by CTT was 30 percent, EMT was 76 percent, and GCT was 92 percent on repeat testing. GCT showed higher titer values in comparison with CTT but was found to be the most precise. EMT titers were comparable to CTT, and its precision was intermediate. Further studies to validate this method are required.

Successful management of acute bleeding in essential thrombocythemia using automated cell separator.

This case represents the challenging role of automated cell separators in management of acute hemorrhagic crisis in a young female patient of essential thrombocythemia. A 17 year old girl having body weight of 41 kg presented to us with profuse nasal bleed. Complete blood counts revealed extremely high platelet counts of 2987×10(9)/l. Due to no response by oral hydroxyurea for last 2 months, urgent mechanical platelet reduction was planned to prevent further complication. A rebound phenomenon of increase in circulating platelet count was observed after every therapeutic platelet reduction. Seven procedures had to be performed on alternate days to bring down the platelet counts to less than 600×10(9)/l. Patient was maintained on oral anagrelide therapy and discharged in a stable condition after 14 days. Therapeutic platelet reduction causes rapid platelet reduction and helps in managing acute complications.

A rare case report of chronic variable immunodeficiency divulged by ABO discrepancy.

ABO discrepancy refers to incongruence between the results of red cell and serum groupings. One such case is described here; the discrepant results of whose routine ABO grouping led to the diagnosis of common variable immunodeficiency. There was no reaction in the reverse grouping of a young patient presenting with recurrent bacterial infections, pointing towards an absence of antibodies in the serum. Diagnosis was made on the basis of markedly decreased serum immunoglobulin levels and by serum protein electrophoresis showing scanty gamma regions.

Prestorage gamma irradiation induces oxidative injury to red cells.

BACKGROUND: Gamma irradiation of blood results in the formation free radicals, which interact with lipids and proteins in the membranes of red blood cells. We have investigated oxidative injury to gamma-irradiated red cells by measuring markers of oxidative injury and its correlation with red cell membrane damage. METHODS: Thirty red cell blood units were irradiated at 25 Gy using Gamma Irradiator (Nordion, Canada) and stored at 4°C for 28 days. Markers of oxidative injury such as MDA levels, methemoglobin formation and osmotic fragility and markers of membrane damage including supernatant Hb, supernatant K(+), and LDH were studied. RESULTS: There was a progressive and statistically significant increase in markers of oxidative injury such as MDA (3.76 v/s 5.01), and methemoglobin formation (1.87 v/s 3.58) in irradiated red cells compared to control non-irradiated cells. Exposure to gamma irradiation caused significant increase in markers of hemolysis such as supernatant Hb (0.087 v/s 0.363), K(+) (35.1 v/s 51.2) and LDH (366.9 v/s 587.4) over the storage period of 28 days. CONCLUSION: Gamma irradiation increases lipid peroxidation and oxidative injury to the red cells.

Reassessment of Critical Anti-D Antibody Titer in RhD Alloimmunized Antenatal Women.

OBJECTIVE: In the setting of RhD-alloimmunized pregnancy, laboratory variations in critical titer (CT) of anti-D antibody may result in needless referrals or a compromised fetal outcome. METHODS: RhD-alloimmunized pregnant women were included. Fetal outcome was categorized based on cord hemoglobin and interventions required. For 3 commonly used CTs of 8, 16, and 32, sensitivity and specificity as well as positive and negative predictive values were computed. RESULTS: When compared with CTs of 16 and 32, we detected 6.9% and 19.4% more cases of moderate-severe hemolytic disease of the fetus and newborn by using 8 as the CT. However, this leads to greater rate of unnecessary referral (12.1%, 10/82) than a CT of 16 (8.2%, 6/73) and 32 (4.9%, 3/61). A CT of 8 demonstrated 100% sensitivity, but 12.1% (10/82) of patients were referred needlessly. CONCLUSION: Because of its 100% sensitivity, we advocate decreasing the CT to 8. However, this may lead to unwarranted referrals.

Establishment of normal reference range of serum hepcidin in Indian blood donors.

BACKGROUND: Hepcidin-25, a polypeptide hormone, plays a major role in iron metabolism and is found to be reduced during iron deficiency; therefore, testing for hepcidin can be utilized as an indicator of bioavailability of iron. Globally, reference range values for hepcidin have been established in different communities. The aim of the present study was to establish the normal reference range values of serum hepcidin in Indian blood donors to fathom the baseline and reference point of hepcidin. MATERIALS AND METHODS: A total of 90 donors fulfilling the eligibility criteria were recruited in the study consisting of 28 males and 62 females. Blood samples collected were used to execute hemoglobin (Hb), serum ferritin, and hepcidin assays. Serum hepcidin-25 isoform was detected by a commercial competitive enzyme-linked immunosorbent assay kit according to the manufacturer's instructions. Hb and ferritin were evaluated by the standard methods. RESULTS: The mean ± standard deviation (SD) of Hb level in males was 14.62 ± 1.34 g/dL and females was 13.33 ± 0.76 g/dL. The mean ± SD of ferritin level in males was 113 ± 56.12 ng/mL and females was 62.65 ± 40.8 ng/mL. Similarly, the mean ± SD of hepcidin level in male donors was 22.18 ± 12.17 ng/mL and female donors was 10.95 ± 6.06 ng/mL. The established reference range values of Hepcidin were 6.32-46.06 ng/mL for males and 3.44-24.78 for females. CONCLUSION: These findings suggest that further studies with larger groups of donors are mandatory to produce reference values of hepcidin that can be précised to the whole populace in India.

Prevalence of the Direct Antiglobulin Test and Its Clinical Impact on Multiply Transfused Thalassemia Patients: A Prospective Study Conducted at a Tertiary Care Center in Northern India.

OBJECTIVE: This study was conducted to estimate prevalence of direct antiglobulin test (DAT) positivity and its impact on transfusion support in patients with thalassemia. METHODS: The DAT testing was performed for patients with ß-thalassemia who received transfusion from November 2021 to March 2022. Elution was done for DAT-positive samples. RESULTS: Of 180 patients, 21 (11.6%) were DAT positive. Immunoglobulin G (IgG) was present in 4 (19%) and IgG+C3d was present in 8 (38%). Only complement was present in 9 (42.8%) patients. The IgG-reactive DATs were associated with pan-reactive eluate. Patients who were DAT-positive had significantly higher levels of serum bilirubin, ferritin, and IgG than those who were DAT-negative. CONCLUSION: Autoantibody formation in multiply transfused thalassemia patients is common and merits equal attention as alloimmunization. It is particularly important as DAT-positive red blood cells may undergo clinically significant hemolysis, which may increase the transfusion requirements with associated sequalae such as increased serum ferritin and splenomegaly.

Effect of donor parameters and cell separators on yield of apheresis platelet and their impact on corrected count increment in aplastic anemia patients.

BACKGROUND: The new cell separators make it simple to collect single donor platelets (SDP), although the platelet yield may vary depending on the cell separator used and donor-related clinical and laboratory variables. AIMS: This study aims to study the factors affecting SDP yield and corrected count increment (CCI). MATERIALS AND METHODS: This retrospective study was carried out at a tertiary care facility in northern India, over 4 years (May 2017-April 2020), data were retrieved and analyzed. STATISTICAL ANALYSIS: Categorical variables were presented as proportions, while continuous variables were presented as mean with standard deviation, P < 0.05 was considered significant. RESULTS: We found a positive correlation between predonation platelet count and yield (r = 0.243, P = 0.000). No such significant correlation was found with Hb concentration (r = 0.025, P = 0.720), age (r = 0.016, P = 0.820), sex (r = -0.038, P = 0.584), and weight (r = -0.025, P = 0.714). Maximum platelet yield and minimum time were seen with Trima. Only 39.3% (33/84) meet the 24 h CCI. The majority of patients did not meet the desired CCI could be due to the patients' clinical condition. On logistic regression, we found a significant association of 24 h CCI with product yield (odds ratio [OR] = 0.168, P = 0.015) and posttransfusion platelet count (OR = 0.454, P < 0.05). CONCLUSION: The only donor-related factor that influences yield is predonation platelet count, whereas 24 h CCI may depend on the clinical status of the patient and yield.

Coronavirus infection and ABO blood grouping: Correlation or coincidence?

Background: Association between the ABO blood group and patient outcomes in COVID-19 patients is still unexplored. A known association may help to understand possible risks in advance to the management of such COVID-19 patients. The present study was designed to test such association if there is any, between the ABO blood group and the severity of COVID-19 patients. Methods: The present hospital-based observational study was conducted at a COVID-19 dedicated tertiary care hospital in North India over a period of six months during the first wave of the pandemic in the country. Five hundred consecutive patients, who tested positive for COVID-19 using RT-PCR on oropharyngeal/nasopharyngeal swabs, admitted to the hospital were included in the study. ABO and Rhesus (Rh) blood grouping was done on leftover hematology blood samples using gel column agglutination technology. Required clinical details of patients including age, gender, clinical symptoms, comorbidities, outcomes, etc., were obtained from the patient's case sheets. Results: The most common blood group was 'B' (42.8%) followed by 'O' (23.4%), and 'A' (22.4%) while the least common was 'AB' (11.4%). Rh positive was seen in 96.2% while 3.8% were negative. Baseline characteristics were comparable including length of hospital stay, duration of symptoms, and associated comorbid illnesses. The need for intensive care unit (ICU) admissions (P = 0.05) and intubations (P = 0.20) was similar across all four blood groups. Differences in the severity of COVID-19 disease and mortalities among the groups were non-significant. Conclusion: There was no observed association found between the ABO blood group and COVID-19 infection requiring hospitalization, ICU admission, intubation, and outcomes. However, there was a higher proportion of breathlessness and the presence of at least one comorbidity in blood group O as compared to others.

Red cell alloimmunization and associated risk factors in multiply transfused thalassemia patients: A prospective cohort study conducted at a tertiary care center in Northern India.

BACKGROUND: One of the complications of chronic transfusions in thalassemia is the development of red cell alloimmunization. AIMS: The aim of the study was to determine the frequency, specificity of red cell alloantibodies, and factors influencing alloimmunization in multiply transfused thalassemia patients. MATERIALS AND METHODS: The study was carried out prospectively on beta-thalassemia patients over 10 months. Plasma samples were used for antibody screening and identification using the column agglutination technique. Patients' clinical, laboratory, and transfusion details were obtained from hospital information system and patient files. STATISTICAL ANALYSIS: Continuous variables were reported as median and quartile, whereas categorical variables were provided as numbers and proportions. P < 0.05 was considered statistically significant. RESULTS: Out of 255 patients, 17 (6.6%) patients developed alloantibodies. Alloimmunized patients had significantly higher median ages at their first transfusions (1 year vs. 0.5 years; P = 0.042) than nonalloimmunized patients. Alloimmunized patients had significantly higher conjugated bilirubin (P = 0.016) and serum ferritin (P = 0.007). The majority of alloantibodies had specificity toward K antigen, followed by E, C, D, JKa, and JKb antigens. Alloimmunized patients received more units per year than nonalloimmunized patients (median, 30 vs. 24 units; P < 0.001). The average transfusion interval time between two successive transfusions showed a significant difference (P < 0.001). CONCLUSIONS: The prevalence of alloimmunization in thalassemia patients in North India is relatively low. Since most of the alloantibodies belong to Rh and Kell blood group system, extended phenotype-matched blood for Rh and Kell will be helpful in further preventing or decreasing the development of alloantibodies in multiply transfused thalassemia patients.

Clinical factors influencing corrected count increment.

Refractoriness to platelet transfusions is a common clinical problem. The present study was conducted to look into patient characteristics affecting the corrected count increment in a tertiary care referral hospital. A total of 161 aphaeresis platelet units were transfused to 40 patients with varied clinical diagnoses. The mean platelet increment was 17,789/mm(3). Median corrected count increment was 7344 and percentage platelet recovery was 22.82%. Logistic regression analysis revealed significant influence of splenomegaly and anti-platelet drugs on refractoriness. Fever, bleeding, sepsis, disseminated intravascular coagulation and cyclosporine use, though more common in the patients with refractoriness they were not statistically significant.

Late onset neonatal anaemia due to maternal anti-Kp(b) induced haemolytic disease of the newborn.

BACKGROUND: Alloanti-Kp(b) is a rare, clinically significant antibody against high frequency red cell antigen Kp(b) of Kell blood group system. We report here a case of Haemolytic disease of newborn (HDN) due to anti-Kp(b), which manifested as severe anaemia at the age of 1 month. AIM: To diagnose and successfully manage anti-Kp(b) induced HDN. METHODOLOGY: Direct antiglobulin test (DAT), antigen typing, irregular antibody screening and identification were done by polyspecific LISS Coombs Gel card and standard methods. RESULTS: At presentation the neonate had severe anemia with reticulocytopenia. Blood group was B, Rh D positive and DAT was 2+. Anti-Kp(b) was detected in mother's serum. Due to unavailability of Kp(b) negative red cells and incompatible blood group of mother (A(1)B Rh D positive) infant was transfused group B Rh D, Kp(b) positive PRBCs under steroid cover. He was symptom free at 4 months of age and DAT became negative at 6 months. CONCLUSION: Anti-Kp(b) is capable of causing severe late HDN. Infants born to irregular antibody positive mothers should be investigated and closely monitored for several weeks after birth for immune HDN even if asymptomatic at birth.

Application of flow cytometry in transfusion medicine: The Sanjay Gandhi Post Graduate Institute of Medical Sciences, India experience.

The application of flow cytometry (FC) is diverse and this powerful tool in used in multiple disciplines such as molecular biology, immunology, cancer biology, virology, and infectious disease screening. FC analyzes a single cell or a particle very rapidly as they flow past single or multiple lasers while suspended in buffered solution. FC has a great impact in the field of transfusion medicine (TM) due to its ability to analyze individual cell population and cell epitopes by sensitive, reproducible, and objective methodologies. The main uses of FC in TM are detection of fetomaternal hemorrhage, diagnosis of paroxysmal nocturnal hemoglobinuria, quantification of D antigen, detection of platelet antibody, quality control of blood components, for example, residual leukocyte counts and evaluation of CD34-positive hematopoietic progenitor cells in stem cell grafts. In recent years, FC has been implemented as an alternative method for the detection and characterization of red cell autoantibodies in autoimmune hemolytic anemia. Many workers considered FC as a very good complement when aberrant expression of various erythrocyte antigens needs to be elucidated. It has been extensively used in the resolution of ABO discrepancies and chimerism study. FC has also been used successfully in various platelet immunological studies. In the recent past, FC has been used in several studies to assess the platelet storage lesions and elucidate granulocyte/monocyte integrity and immunology. FC analysis of CD34+ stem cells is now the method of choice to determine the dosage of the collected progenitor cells. The technique is vastly used to evaluate residual leukocytes in leukodepleted blood components. We conclude that flow cytometers are becoming smaller, cheaper, and more user-friendly and are available in many routine laboratories. FC represents a highly innovative technique for many common diagnostic and scientific fields in TM. Finally, it is the tool of choice to develop and optimize new cellular and immunotherapeutic trials.