Difficulties in the diagnosis of Hb S/Beta thalassemia: Really a mild disease?

A rare -α27.6 deletion compounded with the hemoglobin constant spring mutation identified in a Chinese couple

BACKGROUND

Thalassemia is a common hemoglobin disorder caused by genetic defects in a single autosomal gene. Based on the deficient globin strand, it can be classified as α-thalassemia or β-thalassemia. The 27.6 kb deletion on α-globin related gene cluster (-α27.6) is a rare α-thalassemia variant discovered in 2011, which could affect the detection of common α-thalassemia variants and cause misdiagnosis.

CASE PRESENTATION

An α-thalassemia variant carrying a Chinese couple was reported in this study. The wife was diagnosed at another hospital as αCSα/αCSα but did not manifest corresponding symptoms. After further examinations and in-depth analyses of the results, the genotype of the wife was finally confirmed to be -α27.6/αCSα. Meanwhile, the genotype of the husband was diagnosed as αCSα/αα. The couple requested prenatal diagnosis in the worry of α-thalassemia caused by αCSα/αCSα. Genetic tests on the amniotic fluid reported a mild thalassemia-related genotype of αCSα/αα, on which our suggestion of continuing pregnancy was based.

CONCLUSION

The -α27.6/αCSα case and related manifestations were first reported here expanding the gene spectrum of thalassemia. Such genotype can be misdiagnosed as αCSα/αCSα causing inaccurate estimations of thalassemia risk. To avoid these misdiagnoses, genetic tests for deletions in the related regions were advised when inconsistencies between the genotype and the phenotype were discovered.

Current obstetric outcomes in Jamaican women with sickle hemoglobinopathy - a balance of risks for aspirin?

OBJECTIVES

Sickle cell disease (SCD) occurs in 2.8 % of our Jamaican antenatal population with homozygous HbSS being most associated with adverse maternal and perinatal outcomes.

METHODS

A retrospective comparative analysis of HbSS, HbSC and HbSβThal pregnancy outcomes at the University Hospital of the West Indies (UHWI) between January 2012 and December 2022 was conducted.

RESULTS

Of 120 patients (138 pregnancies), obesity occurred in 36 % (20/56) of the 'non-HbSS' group, i.e. HbSβThal (55 %, 5/9) and HbSC (32 %, 15/47) combined vs. 9.7 % of the HbSS (8/82). HbSS patients had more crises requiring transfusions, acute chest syndrome (ACS), maternal 'near-misses' (OR=10.7, 95 % 3.5-32.3; p<0.001), hospitalizations (OR 7.6, 95 % CI 3.4-16.9; p<0.001), low birth weight (LBW) neonates (OR 3.1, 1.1-8.9; p=0.037) and preterm birth (OR=2.6, 1.2-5.8; p=0.018) compared to HbSC and HbSβThal. Low dose aspirin was prescribed in 43 %. Logistic regression showed those NOT on aspirin (n=76) had more miscarriages (22 v. 2 %), were LESS likely to have a live birth (75 v. 95 % (0.2, 0.04-0.57, p=0.005)), but surprisingly had fewer painful crises (28 v. 46 % (0.5, 0.03-0.9, p=0.03)).

CONCLUSIONS

HbSS women had a 10-fold excess of maternal near-misses. Additional research may further clarify the effects of aspirin on pregnancy outcomes as related to SCD genotypes.

Comparison of screening indicators for different types of thalassemia carriers in Hunan Province

Background

Carrier screening is the most effective method to block the occurrence of thalassemia. However, due to differences in race and genotype, MCV, MCH, HbA2 and other indicators are far from each other. The purpose of this study is to evaluate the common screening indicators of a, b and ab-compound thalassemia carriers in Hunan Province, and try to use the relevant formulas in the existing literature to predict and distinguish different types of thalassemia carriers.

Methods

Receiver operating characteristic curve (ROC curve) combined with Youden index was utilized to analyze results of blood routine examination, hemoglobin electrophoresis, and literature-related formulas for 1111 a-thalassemia carriers, 464 b-thalassemia carriers and 24 ab-thalassemia carriers.

Sickle Cell Disease Update: New Treatments and Challenging Nutritional Interventions

Sickle cell disease (SCD), a distinctive and often overlooked illness in the 21st century, is a congenital blood disorder characterized by considerable phenotypic diversity. It comprises a group of disorders, with sickle cell anemia (SCA) being the most prevalent and serious genotype. Although there have been some systematic reviews of global data, worldwide statistics regarding SCD prevalence, morbidity, and mortality remain scarce. In developed countries with a lower number of sickle cell patients, cutting-edge technologies have led to the development of new treatments. However, in developing settings where sickle cell disease (SCD) is more prevalent, medical management, rather than a cure, still relies on the use of hydroxyurea, blood transfusions, and analgesics. This is a disease that affects red blood cells, consequently affecting most organs in diverse manners. We discuss its etiology and the advent of new technologies, but the aim of this study is to understand the various types of nutrition-related studies involving individuals suffering from SCD, particularly in Africa. The interplay of the environment, food, gut microbiota, along with their respective genomes collectively known as the gut microbiome, and host metabolism is responsible for mediating host metabolic phenotypes and modulating gut microbiota. In addition, it serves the purpose of providing essential nutrients. Moreover, it engages in direct interactions with host homeostasis and the immune system, as well as indirect interactions via metabolites. Nutrition interventions and nutritional care are mechanisms for addressing increased nutrient expenditures and are important aspects of supportive management for patients with SCD. Underprivileged areas in Sub-Saharan Africa should be accompanied by efforts to define and promote of the nutritional aspects of SCD. Their importance is key to maintaining well-being and quality of life, especially because new technologies and products remain limited, while the use of native medicinal plant resources is acknowledged.

Scalable noninvasive amplicon-based precision sequencing (SNAPseq) for genetic diagnosis and screening of β-thalassemia and sickle cell disease using a next-generation sequencing platform

β-hemoglobinopathies such as β-thalassemia (BT) and Sickle cell disease (SCD) are inherited monogenic blood disorders with significant global burden. Hence, early and affordable diagnosis can alleviate morbidity and reduce mortality given the lack of effective cure. Currently, Sanger sequencing is considered to be the gold standard genetic test for BT and SCD, but it has a very low throughput requiring multiple amplicons and more sequencing reactions to cover the entire HBB gene. To address this, we have demonstrated an extraction-free single amplicon-based approach for screening the entire β-globin gene with clinical samples using Scalable noninvasive amplicon-based precision sequencing (SNAPseq) assay catalyzing with next-generation sequencing (NGS). We optimized the assay using noninvasive buccal swab samples and simple finger prick blood for direct amplification with crude lysates. SNAPseq demonstrates high sensitivity and specificity, having a 100% agreement with Sanger sequencing. Furthermore, to facilitate seamless reporting, we have created a much simpler automated pipeline with comprehensive resources for pathogenic mutations in BT and SCD through data integration after systematic classification of variants according to ACMG and AMP guidelines. To the best of our knowledge, this is the first report of the NGS-based high throughput SNAPseq approach for the detection of both BT and SCD in a single assay with high sensitivity in an automated pipeline.

Evaluation of the validity of the pre-marriage mean corpuscular volume value as a predictive test for b-thalassemia carrier status

Background

The national mandatory premarital screening test is based on mean corpuscular volume (MCV) > 80 fL value for the detection of β-thalassemia to provide acceptance for marriage. The objective of this study is to assess the efficacy of MCV as a screening test for β-thalassemia trait in the present population.

Methods

This study was conducted on 418 blood samples collected from adult individuals. The diagnosis of β-thalassemia carrier was given to those having HbA2 values equal to or above 3.5%. The diagnostic reliability of different RBC indices and formulas in discriminating cases of β-thalassemia trait were evaluated. Finally, a new index called "Momani" was determined based on MCV, RDW and RBC count.

Results

β-thalassemia trait was identified in 10% of the cases. The measured MCV value was significantly lower in β-thalassemia carrier group compared to non-carrier group (p = <0.001). MCV value and RBC count showed a higher diagnostic reliability than other RBC indices. We found that MCV ≤ 74.45 fL is more suitable cutoff value of MCV with 86.2% specificity, 71.4% sensitivity, 36.6% positive predictive value, and 96.4% negative predictive value. Finally, our index "Momani" was found to be useful in predicting carrier and paralleled the performance of Sirdah, Mentzer, and Ehsani indices.

Conclusions

MCV<80 is a useful but not a perfect cutoff point for the screening of β-thalassemia carriers from noncarriers. The diagnostic accuracy of MCV can be improved by selecting a new cutoff value. Moreover, "Momani" index shows good discrimination ability in diagnosing β-thalassemia carrier in our population.