Blood Grouping Research Articles

A Rare B-Subgroup Causing ABO Discrepancy in Blood Grouping: A Case Report

This is a 24-year-old gentleman with underlying status epilepticus, admitted for septic shock secondary to meningoencephalitis. On pretransfusion investigation, his blood grouping showed ABO discrepancy. His forward grouping showed negative reaction with anti-A, and anti-B while his reverse grouping showed strong 3+ reaction with A1 cell and no reaction with B cell. Repeated tests with new samples also showed similar results. Subsequently, test was repeated at room temperature and 4◦C with prolonged incubation and with enzyme treated cells. Forward grouping showed the same result while the reverse grouping showed enhancement with A1 cell (4+). We suspected B subgroup and proceeded with anti-H lectin test which showed 4+ reaction. Adsorption and elution study confirmed the presence of antigen B on patient’s RBCs. Therefore, it is necessary to resolve all discrepancies to ensure safe transfusion practice.International Journal of Human and Health Sciences Vol. 08 No. 01 Jan’24 Page: 99-102

Frequency of Rh and Kell antigens among blood donors: A retrospective analysis from a tertiary care center in Eastern India

Objectives: The phenotyping of Rh and Kell antigens plays a major role in preventing alloimmunization and adverse events in multi-transfused patients. This study tries to highlight the frequency of Rh and Kell antigens among the blood donors who donated blood at a tertiary care center located in Eastern India. Material and Methods: The study was conducted in the Department of Transfusion Medicine and Blood Bank of All India Institute of Medical Sciences, Patna, from January 2021 to March 2023 on 10,032 whole blood donors of blood groups A, B, O, and AB by column agglutination technique using gel cards for blood grouping and phenotyping. Results: A total of 10,032 whole blood donors of groups A, B, O, and AB were included in the study. The frequency of “D” antigen was 95.77% (n = 9,608), “C” was 90.47% (n = 9,076), “c” was 50.47% (n = 5,063), “E” was 15.9% (n = 1,595), “e” was 99% (n = 9,932), and “K” was 2.67% (n = 268). “c” antigen frequency was 45.81–49.48% in RhD positive blood groups and 100% in all the RhD negative blood groups while “C” antigen frequency was 92.04–94.68% in RhD positive blood groups, and 4–24.13% in RhD negative blood groups. Conclusion: Since pre-transfusion phenotyping in multi-transfusion patients is not routinely practiced, transfusion of at least Rh and Kell phenotyped donor red cells can lead to a great decrease in the risk of alloimmunization and adverse events related to transfusion.

Evaluation, Exploration and Management Strategies of a First Reported Rarest Case of Para-Bombay Blood Phenotype with E-Beta Thalassaemia from Bangladesh

Human H/h genetic polymorphism in ABO blood group system is rare and evidenced with Bombay and Para-Bombay blood group. This patient a 27-year-old-young man having ‘E-Beta thalassaemia’ incidentally has been identified as a case of ‘Para-Bombay phenotype’ after exploring with proper blood grouping, antibody detection and saliva inhibition study. Previously he was diagnosed as ‘O’ RhD positive and had two events of transfusion reaction during ‘O’ positive blood transfusion. In literature search and browsing there is dearth information on Para-Bombay Phenotype with E-Beta Thalassaemia. So far to our knowledge, this is the first reported case from Bangladesh of patient having ‘E-Beta Thalassaemia’ evidenced with rare ‘Para-Bombay blood Phenotype’. This study explores the laboratory work-out on Para-Bombay Phenotype and evaluates treatment strategies on this phenotype with concomitant E-Beta Thalassaemia. J Bangladesh Coll Phys Surg 2024; 42: 97-104

Fully genotyping and screening of clinically important blood-group antigens by MALDI TOF mass spectrometry.

Several molecular biology methods are available for high-throughput blood typing. In this study, we aimed to build a high-throughput blood-group genetic screening system for high-frequency blood-group antigen-negative rare-blood groups in donors and patients. The amplification primers for all blood-type gene fragments involving the selected alleles were designed for detection. Single-base extend primers were also designed based on specific loci. DNA fragments were detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MS) for the last nucleotide identification of amplification products in the extend step. The accuracy was verified by known samples. Thirty-six random samples were detected by serological tests and sequencing to verify the system stability. After verification, according to the collected known rare-blood-type samples, all the alleles designed to be detected matched with the validated single-nucleotide polymorphisms. The verification tests showed that all genotyping results of the random samples were in accordance with the findings of serotyping and sequencing. Then, 1258 random donor samples were screened by the built typing system after the verification. Three Fy(a-) and four s- were screened out in 1258 random blood samples. The multiple polymerase chain reaction-based MS detection system can be used in rare-blood-type screening with good accuracy and stability.

Cold Agglutinin Disease Unfurled in Laboratory and Blood Bank: A Little Poignant Observation Can Speak a Lot!

Autoimmune hemolytic anemias (AIHAs) are hemolytic anemias characterized by the production of autoantibodies against surface antigens on red blood cells. Cold agglutinin disease (CAD) is a relatively rare subcategory of AIHA, affecting mainly the middle-aged with anemia often being the presenting symptom. We present a case of a middle-aged female who was admitted for severe anemia under evaluation. A discrepancy in blood grouping was noted when request for blood transfusion was received in a blood bank, owing to autoantibodies interfering in testing. Routine complete blood counts showed temperature-based variations. A detailed workup confirmed a diagnosis of CA type of AIHA. The case reiterates the importance of good interdepartmental coordination between clinicians, laboratory, and blood bank, which helped clinch the diagnosis of CAD through the correlation of clinical findings, blood counts, and immunological and biochemical parameters.

Incidence of ABO Blood Groups in Patients with Oral Cancer, Premalignant Conditions, and Lesions: A Prospective Observational Study

Abstract Aim of the Study: The aim was to assess the incidence and to correlate ABO blood groups in patients with oral cancer, premalignant conditions, and lesions. Materials and Methods: It is a prospective observational study. ABO blood grouping was done on 120 cases, of which 60 were with oral cancer, 20 with oral submucous fibrosis, 20 with leukoplakia, and 20 with lichen planus. About 120 healthy subjects were selected after randomization. The obtained data were subjected to statistical analysis. Results: Out of 120 precancerous and cancerous cases, 26 had blood group A (21.6%), 46 had blood group B (38.3%), 5 had blood group AB (4.2%), and 43 had blood group O (35.83%). Among the controls, out of 120 subjects, 24 had blood group A (20%), 40 had blood group B (33.33%), 5 had blood group AB (4.2%), and 51 had blood group O (42.5%). The strength of association between was assessed using the odd’s ratio and found that people with blood group B had 1.24 times higher risk of developing oral precancerous and cancerous lesions compared to people of other blood groups. The relative risk was 1.11 for people with blood group A and 1 for those with blood group AB. The relative risk for people with blood group O was 0.75. Conclusions: In the present study, it was found that people with blood group B are at a greater risk of developing oral malignancies, followed by those with blood group A, AB, and O.

Exploring the Link: A Cross-Sectional Study on the Correlation Between Periodontal Health and ABO & Rh Blood Group Phenotype in Intellectually Disabled Individuals of Dakshina Kannada District

Background and Aim Across the globe individuals with intellectual disabilities ID are frequently noted to exhibit inferior oral hygiene and periodontal health. Previous research has demonstrated a link between periodontal health and blood grouping among apparently healthy individuals with periodontitis patients. This study attempted to assess a relationship between periodontal health and blood grouping phenotypes among individuals with intellectual disabilities in Dakshina Kannada District.Methods In Dakshina Kannada district a cross-sectional survey was conducted among 548 intellectually disabled individuals enrolled in special needs institutions. Among them 115 individuals were identified as having Down syndrome while the remaining 433 individuals had other intellectual disabilities. During the survey oral hygiene indices such as Oral Hygiene Index Simplified OHI-S Gingival index GI and Periodontal Screening and Recording PSR index were measured and ABO blood group patterns were established through self-reports verified by medical records.Results Among 548 intellectually disabled individuals distribution of blood group was as follows 32.11 had blood group A 26.64 had blood group B 23.90 had blood group O and 17.33 had blood group AB. Results of our research indicated that Down syndrome individuals with blood group lsquoOrsquo 41.7 and Rh lsquopositiversquo 58.26 were more susceptible to periodontitis.Conclusion Among intellectually disabled individuals there exists a robust correlation between periodontal health and ABO blood group phenotypes.

Prospective study of ABO and Rh blood group frequency and distribution among health-care professional students at Hassan Institute of Medical Sciences, Hassan

Background: The presence of immunologically competent agglutinogens in ABO and Rhesus (Rh) system makes these blood groups clinically important. The distribution frequency of these blood groups in various geographical regions is essential for the maintenance of blood bank records, for research studies, etc. This helps in safe transfusion during emergency. Many population-based research works were conducted on the prevalence of blood agglutinogens. The lack of data on these blood antigens among young health-care professional students prompted the conduct of this study on blood groups. Aims and Objectives: The aims and objectives of the study are to ascertain blood group frequencies among health-care professional students and to obtain prospective group of Rh-negative blood donor database. Materials and Methods: Research was accomplished on 400 health-care professional students of HIMS, Hassan, in department of physiology after going through knowledge, attitude, and practice questionnaire. Blood grouping was done by collecting blood from participants by finger prick method on glass slides. Results: In participants, the most common blood group was O (40.8%) with decreasing prevalence of B (34.3%), A (18%), and AB (7%). The frequency of Rh-positive and negative groups was 95.5% and 4.5%, respectively. Conclusion: Among participants, blood group O and blood group AB was most and least common, respectively. The frequency of Rh positive was far higher compared to Rh-negative groups.

Blood Group Discrepancy in a Donor Due to a Rare Ax/Aweak Subgroup Phenotype with ABO*AW.31.01/*O.01.75 Genotype

ABSTRACT The most crucial blood group system in transfusion medicine is still the ABO system. Any unresolved discrepancy could result in the patient receiving blood that is incompatible and could trigger acute intravascular hemolysis. ABO subgroups are one of the astounding differences in blood grouping. The amount of A and B antigens carried by red blood cells and present in secretion varies depending on the ABO subgroup phenotype. Clinically, A1 and A2 are the two most frequently observed subtypes. Many weaker A subgroups have been described, including A3, Axe, am, and el. This example involves an Indian male donor who was initially misclassified as a Group O individual before being identified as an Ax/Aweak subgroup phenotypically. The next-generation sequencing defined the genotype of this case as ABO*AW.31.01/*O.01.75.

Identification and Blood Transfusion of a Rare A1.02/BA.02 Genotype.

The aim was to analyze the serological and molecular genetic characteristics of a rare B(A) subtype pedigree, explore its pathogenesis, and discuss transfusion strategies. ABO blood typing serological tests were conducted on a female subject and her family member using standard serological methods. Sequencing analysis of the ABO gene exons 6 and 7 was performed using PCR technique for the female subject and her family member to examine the blood types of the participants. The serological test results showed a discrepancy between the forward and reverse typings of the female subject. The forward typing was similar to that of AB subtype serological forward typing, while the reverse typing indicated AB blood type. Based on the sequencing results, it is inferred that the female subject and her son have 8 mutations on one BA.02 chain: 297A>G, 526C>G, 657C>T, 700C>G, 703G>A, 796C>A, 803G>C, and 930G>A. Comparing these eight mutation sites with the Blood Group Antigen Gene Mutation Database (BGMUT), it was found that the female subject had a heterozygous mutation at c.700C>G in the 7th exon of the B.01 gene, consistent with the characteristics of the BA.02 allele. The genotype of the female subject was determined as A1.02/ BA.02, while the genotype of her son was determined as O.01.01/BA.02. The serological presentation of the B(A) subtype for the female subject reported in this study was unique. It differed from previously reported cases, indicating that the determination of B(A) subtypes cannot solely rely on serological testing. It requires a comprehensive analysis combining the results of genetic testing and pedigree investigation.

Naturally occurring clinically significant anti-M alloantibodies with wide thermal range: A series of three cases

Abstract: Anti-M antibodies are usually of the immunoglobulin (Ig)-M type and have a cold thermal range, which is generally considered clinically insignificant. However, in some cases, there may also be an IgG component present exclusively. In addition to the discrepancy in blood grouping (attributable to the IgM component), the presence of an IgG component reacting at 37°C can interfere with pretransfusion testing, making it difficult to find fully compatible blood within a short time. In this report, we discuss three children: two boys aged five and 1½ years, respectively, and a female toddler aged 1 year who were all successfully treated using M-antigen negative packed red blood cells along with the standard treatment plan of the hospital. This was made possible by an established institutional blood donor registry comprising O-typed blood donors (n = 374), who were phenotyped for 21 erythrocyte antigens using commercially available monoclonal antisera (Ortho Clinical Diagnostics, Pvt Ltd., Mumbai, India).

Impact of Anti-M on Grouping and Cross Matching: The Challenges Faced in Three Cases

Anti-M, a frequently encountered antibody of the MNS blood group system, is commonly regarded as a naturally occurring saline agglutinin that can occasionally exhibit clinically significant behaviour. Particularly when reactive at 37°C or during the antiglobulin phase, it can complicate pretransfusion testing and patient management in the blood bank. Three distinct cases (2 males. 1 female) in varying clinical scenarios, ranging from surgery to acute coronary syndrome, are described. The present cases presented discrepancies in blood grouping and compatibility testing, highlighting the challenges posed by the presence of Anti-M antibodies that react at or above room temperature and during the antiglobulin phase, thus defying the usual expectations. It is imperative to provide antigen-negative red cells and those that are compatible by an Indirect Antiglobulin Test (IAT) when Anti-M is reactive at 37°C to ensure safe transfusion. Hence, there is a need to underscore the potential clinical implications in transfusion medicine, as well as the nuances of detecting, identifying, and managing the presence of Anti-M antibodies in patients requiring transfusion.

DEL phenotype in RhD-negative North Indian blood donors.

Rh-DEL type is not detected on routine serology and requires specialized adsorption elution methods which are laborious. Identifying the DEL phenotype in blood donors is important to prevent alloimmunization in transfusion recipients. The present study aimed to determine the frequency of DEL phenotype in RhD-negative North Indian blood donors and correlate the results with Rh Cc/Ee phenotype. In this prospective descriptive cross-sectional study, a total of 205 blood donors with historic blood group RhD-negative were enrolled. All samples were subjected to blood grouping using a fully automated immunohematology analyzer and samples that typed as RhD negative by two different anti-D antisera were tested for Weak D. Weak D-negative samples were subjected to adsorption and elution for DEL phenotype. All samples were also tested for extended Rh phenotype for C/c and E/e antigens. Of the total 11934 donors during the study, 6.2% (n = 743) donors were RhD negative. Of the 205 donors enrolled in the study, two donor samples were serologically weak D positive. None of the remaining 203 donors tested positive for the DEL phenotype. The extended Rh phenotype performed for these donors showed that 6.83% (n = 14) donors were positive for RhC antigen and 1.46% (n = 3) were positive for Rh E antigen. Both weak D-positive donors were also positive for the Rh C antigen. The prevalence of DEL phenotype is low in the Indian population and studies with larger sample sizes are required to determine the effectiveness of routine C/E typing as a strategy to identify DEL-positive individuals.

Biological Abnormalities of Hemostasis in Patients with Epistaxis or Menorrhagia in Yaoundé, Cameroon.

In Cameroon, screening and diagnosis of minor hemorrhagic syndromes remain difficult and few research studies have been done to assess the magnitude of future bleeding risk and the burden of these disorders on quality of life. Epistaxis and menorrhagia are the two leading causes of bleeding disorders in the world population. The aim of this study was to investigate the biological abnormalities of hemostasis in patients with epistaxis and menorrhagia. From January to December 2021, we conducted a cross-sectional study in six hospitals with a gynecology and ENT department. We selected patients who presented epistasis or menorrhagia through clinical file and made them pass an interview and biological exams. Venous blood collected on EDTA tube allowed us to measure full blood count, thin blood smear, and blood grouping. PT, APPT, and fibrinogen assay were measured from citrate platelet-poor plasma. This plasma stored at -20°C for a maximum of 3 months allowed us to measure vWF : Ag and vWF : CBA ELISA. The bleeding time was measured at the time of sampling. In total, our study population consisted of 60 patients aged 01-45 years. Epistaxis (40%) and menorrhagia (29%) were the two main causes of bleeding complaints in our study, in addition to gingivorrhagia (15%) and prolonged bleeding after injury (03%). Almost 60% of the population had at least one abnormal hemostasis parameter. The main abnormalities found were low von Willebrand factor (30.19%), presence of macroplatelets (16.98%), prolonged bleeding time (15.09%), prolonged PT (15.09%), and low platelet count (¬07.55%). In Cameroon, bleeding disorders manifested by epistaxis and menorrhagia are mainly caused by abnormalities of primary hemostasis.

Prevalence and Characterisation of Irregular RBC Antibodies in Antenatal Females from a Tertiary Care Center in Northern India: A Cross-sectional Study

Introduction: Haemolytic Disease of the Foetus and Newborn (HDFN) is widely known to be caused by the presence of irregular Red Blood Cell (RBC) antibodies in pregnant females. To prevent HDFN, it is crucial to identify these antibodies in pregnant women. Aim: To evaluate the prevalence of irregular red cell antibodies in pregnant women in a tertiary care hospital. Materials and Methods: A cross-sectional retrospective study was conducted in the Department of Transfusion Medicine at Indraprastha Apollo New Delhi, from November 2009 to December 2017. A total of 8,217 prenatal females were examined for irregular red cell antibodies. Antibody screening and blood grouping were performed. The Capture-R ready screen was used to confirm screen-positive tests. Adsorption, elution, and other advanced techniques were utilised as needed. Data was collected from patient records and entered into a Microsoft excel spreadsheet. The statistical analysis was conducted using Statistical Package for Social Sciences (SPSS) software version 14.0 (USA). Statistical tests, including the Chi-squared and Fisher’s exact test, were performed, with a p-value less than 0.05 considered statistically significant. Results: Out of the 8,217 prenatal females examined, 105 (1.27%) had positive screening results with the four cell panel. Red cell alloimmunisation was observed in groups that were RhD negative (n=93/105; 88.57%) and positive (n=12/105; 11.42%). The most prevalent alloantibody among RhD negative individuals was alloantibody anti-D (n= 83/93; 89.24%), followed by alloantibody anti C+ anti D (n=13/93; 13.97%). Anti-D was the most prevalent alloantibody overall (n=83/105; 79.04%). Conclusion: Alloimmunisation rates were notably high among women lacking the Rh D antigen. Individuals with a history of adverse obstetric outcomes showed a statistically significant association with alloimmunisation. Therefore, it is recommended to screen such individuals for alloantibodies to enable early detection and improve the management of HDFN.

Value of Chest Computed Tomography in Diagnosis of COVID-19 Related Pneumonia and Its Severity in Relation to ABO Blood Grouping System

Value of Chest Computed Tomography in Diagnosis of COVID-19 Related Pneumonia and Its Severity in Relation to ABO Blood Grouping System

CRISPR/Cas13a-based single-nucleotide polymorphism detection for reliable determination of ABO blood group genotypes.

The ABO blood group plays an important role in blood transfusion, linkage analysis, individual identification, etc. Serologic methods of blood typing are gold standards for the time being, which require stable typing antisera and fresh blood samples and are labor intensive. At present, reliable determination of ABO blood group genotypes based on single-nucleotide polymorphisms (SNPs) among A, B, and O alleles remains necessary. Thus, in this work, CRISPR/Cas13a-mediated genotyping for the ABO blood group by detecting SNPs between different alleles was proposed. The ABO*O.01.01(c.261delG) allele (G for the A/B allele and del for the O allele) and ABO*B.01(c.796C > A) allele (C for the A/O allele and A for the B allele) were selected to determine the six genotypes (AA, AO, BB, BO, OO, and AB) of the ABO blood group. Multiplex PCR was adapted to simultaneously amplify the two loci. CRISPR/Cas13a was then used to specifically differentiate ABO*O.01.01(c.261delG) and ABO*B.01(c.796C > A) of A, B, and O alleles. Highly accurate determination of different genotypes was achieved with a limit of detection of 50 pg per reaction within 60 min. The reliability of this method was further validated based on its applicability in detecting buccal swab samples with six genotypes. The results were compared with those of serological and sequencing methods, with 100% accuracy. Thus, the CRISPR/Cas13a-mediated assay shows great application potential in the reliable identification of ABO blood group genotypes in a wide range of samples, eliminating the need to collect fresh blood samples in the traditional method.

Association of Cholesterol and Superoxide Dismutase in Patients with Polycystic Ovary Syndrome

Background: Polycystic ovary syndrome (PCOS) is a hormonal condition affecting 4-20% of women globally. It causes abnormal androgen production, obesity, irregular menstrual cycles, and increases the risk of diabetes. This study aims to investigate the relationship between SOD activity and cholesterol levels in PCOS women of different ages and blood types. Methodology: It is original research, in which we draw blood samples from disease and control patients, and after blood grouping and centrifugation we performed the SOD activity with an ELISA kit and then we performed the lipid profiling with the help of Beckman coulter which ensure the level of cholesterol, HDL and triglyceride in disease patients which vary in every age and blood group. Results: The results show that the SOD value is higher in the age group 26-30 and blood group B+ve, whereas in lipid profiling it also varies in both age and blood group. The value of triglyceride was found higher in blood group A-ve and showed hype in the age group 36-40. The level of cholesterol was found to be higher in blood group A-ve and increased with the age group of 26-30 years. The value of HDL was found higher in the age group 21-25 with blood group O-ve. Conclusion: This study revealed consistently high levels of cholesterol and HDL across all age and blood groups, while triglyceride and SOD levels exhibited inconsistent elevation among different groups. The study's primary limitation is its small sample size, preventing generalizability. To address this, it's recommended that research focus on diverse risk factors influencing cholesterol, HDL, and SOD levels. This approach can lead to improved variable control within the local population, enabling the development of effective strategies for mitigating these elevations and reducing associated health risks.

To Assess the Knowledge and Determinants Associated with Blood Donor at National Medical College & Teaching Hospital, Birgunj

Introduction: In clinical practice, the two most crucial systems of blood grouping are ABO and Rh. There exist four primary blood types, namely A, B, AB and O. World Health Organization advocates for the compulsory screening of all blood donations prior to usage, with HIV, hepatitis B and C, as well as syphilis being mandatory. The aim of the study is to assess the knowledge and determinants associated with blood donors at National Medical College & Teaching Hospital, Birgunj.Materials and Methods: Proposal was reviewed by the Institutional Review Committee of National Medical College and approved on 9th July 2023. (Ref. F-NMC/662/079-080). A descriptive cross-sectional study was done in the blood donation programs organized in the premises of National Medical College. Sampling method used was census.Results: Of the total particiants, 41.3 % were overweight followed by 39.1 % who showed the normal weight and 7.6 % of the people were found to be underweight. The upper middle-class group accounted for 71.7 % of the total respondents, knowledge about how frequently a person can donate the blood were in 38(41.31%), the volume of blood collected in one pint at the time of donation was 33(35.86%), time taken nearly 5-8 minutes were 64 (69.56%). Among the donors 17(18.47%) had donated for first time in their life similarly for second time and more than three times were 38(41.31%), 38(41.31%), 26(28.26%) and 11(11.95%), respectively.Conclusion: The overall level of knowledge was satisfactory. Male participants had more practice regarding blood donation rather than females. Community shall be benefited by similar set up as made by health workers, blood bank and hospital.

Do Blood group and Sickle cell trait protect against placental malaria?

Blood group O is reported to confer some degree of protection from severe malaria in endemic setting. This protection is believed to be due to reduced and smaller rosette formation in people of blood group O which can easily be cleared by the host immune system. Also, sickle cell trait (HbAS) is reported to disrupt the adhesion of infected erythrocytes to microvascular endothelial walls, which could protect pregnant women from placental malaria. We determined the association between HbAS and ABO blood group, and placental malaria amongst pregnant women of all parities. The study enrolled 221 pregnant women. Peripheral blood samples were taken for malaria smears, ABO blood grouping and haemoglobin (Hb) electrophoresis. A struc‑ tured questionnaire was used to age, bed net usage, and the number of Sulphadoxine‑pyrimethamine (SP) doses taken by a pregnant woman. Two hundred and twenty‑one (221) pregnant women were enrolled and out of this number, 110 (49.8%) were primiparae and 111 (50.2%) multiparae, with a mean age of 23.7±5.2. Placental malaria (PM) prevalence by PCR detection was 19.4% (43/221). Of those who were malaria positive 58.1% (25/43) were primiparae. Primiparae who are of blood group O were more susceptible to PM [P=0.04, (OR); 2.85, 95% (Cl), 1.12‑9.01]. But sickle cell trait did not reduce the prevalence of PM [P=0.84 (OR); 0.92, 95% (Cl), 0.43‑1.99]. Non‑blood group O primiparae women were protected against placental malaria. This could be why some primiparae women are protected from PM, just like multiparae women.