Evaluation of a prenatal screening procedure for beta-thalassaemia carriers in a Chinese population based on the mean corpuscular volume (MCV)

Hemoglobin A2 (HbA2) has a measure of unreliability in diagnosing β-thalassemia trait (β-TT)

INTRODUCTION

Detection of β-thalassemia trait or carriers (β-TT) depends significantly on an increase in Hemoglobin A₂ (HbA₂) levels, which is found at low levels (<3%) in normal healthy individuals and elevated levels (≥3.5%) in β-TT individuals. The study was designed to evaluate the reliability of the diagnostic parameter HbA₂ in the differentiation of β-TT and non-β-TT in Saudis.

METHODS

The widely used high performance liquid chromatography (Variant II Bio-Rad) was used to measure HbA₂ levels in blood. Sanger sequencing was used to screen the variation in globin genes (HBB, HBD, HBA1, and HBA2). All the study subjects were divided into βTT and non-βTT (wild) categories based on the presence or absence of HBB variations and further sub-divided into false positive, true positive, false negative, and true negative, based on HbA₂ values.

RESULTS

Out of 288 samples, 96 had HBB gene mutations. Of the 96 β-TT samples, sickle cell trait (SCT) samples (n = 58) were excluded, while the remaining (38 β-TT) were included in the detailed analysis: seven subjects with the HBB mutation had normal HbA₂ (<3%), and three were borderline (3.1-3.9%). The remainder (n = 28) had an elevated HbA₂ level (>4%). Based on HbA₂ analysis alone, both these groups would be incorrectly diagnosed as normal. Similarly, of the 189 non-β-TT samples, 179 had normal HbA₂, eight had borderline HbA₂, and two had a HbA₂ level above 4%. Based on HbA₂ analysis alone, borderline and >4% HbA₂ individuals, negative for β-TT, can be incorrectly diagnosed as carriers.

CONCLUSION

Given the percentage of samples falling in the HbA₂ "borderline" and "normal" categories, it can be concluded that HbA₂ has a measure of unreliability in the diagnosis of β-thalassemia carriers.

The role of discriminant functions in screening beta thalassemia trait and iron deficiency anemia among laboratory samples

INTRODUCTION

Most important differential diagnosis for microcytosis and hypochromia is beta thalassemia trait (BTT) and iron deficiency anemia.

AIM

To study the utility of discriminant functions (DFs) and red cell indices in distinguishing BTT and iron deficiency anemia.

METHODS

The study is observational (cross sectional). A total of 350 patients, 43 BTT, and 307 iron-deficiency anemia reflecting actual disease prevalence were included. Their complete red blood cell parameters, hemoglobin A2, and serum ferritin level wherever required were obtained. Receiver operator characteristic curve was drawn for each DF and results compared with other studies.

RESULTS

Among the six DFs, the highest sensitivity (97.7%) and specificity (98.6%) was shown, respectively, by Shine and Lal (S and L) and England and Fraser index (E and F) in identifying cases of BTT. Youden index of the Mentzer index (MI) was the highest (69.0) and S and L, the lowest (13.2) indicating MI to be the most efficient and the S and L, the least in differentiating the two entities. Red cell distribution width index (RDWI) showed the highest accuracy (91.6%), whereas S and L showed the least accuracy (29.6%).

CONCLUSION

MI was the most efficient in discriminating BTT from iron deficiency anemia (IDA). RDWI stands to be the most accurate. S and L could at best be used as screening tool rather than DF. No study except one agreed with us because convenient sampling used in other studies generated bias in their results. Statistically, this study bears far more relevance than other studies because the sample distribution reflects the prevalence of IDA and BTT in the community.

ASCI 2010 standardized practice protocol for cardiac magnetic resonance imaging: a report of the Asian society of cardiovascular imaging cardiac computed tomography and cardiac magnetic resonance imaging guideline working group

These practice guidelines are recommended by the Asian Society of Cardiovascular Imaging (ASCI), the sole society in Asia designated for cardiovascular imaging, to provide a framework to healthcare providers for suggested essential elements in cardiac magnetic resonance (CMR) examinations of different disease spectra. The guideline is composed of recommendations on the general technique, acquisition of some basic modules, and protocols on stress tests. The protocols for specific diseases are provided in a table format for quick reference to be easily utilized for everyday clinical CMR.

A comparison of the accuracy of the corpuscular fragility and mean corpuscular volume tests for the alpha-thalassemia 1 and beta-thalassemia traits

OBJECTIVE

To compare the accuracy of the osmotic fragility test (OFT) and mean corpuscular volume (MCV) calculation when screening for the alpha-thalassemia 1 and/or beta-thalassemia trait.

METHOD

In this cross-sectional study, blood samples from 328 apparently healthy pregnant women were sent on the same day to separate laboratories for the OFT (performed using a glycerol 0.45%, phosphate-buffered, sodium chloride solution) and MCV testing (by means of a standard automated hematology analyzer). A polymerase chain reaction was also performed to positively diagnose alpha-thalassemia 1 carriers, and a quantitative HbA(2) test to positively diagnose beta-thalassemia carriers.

RESULTS

Sensitivity and specificity were 95.0% and 86% for the OFT; and based on the cut-off point of 78.1 fL derived from the ROC curve, they were 93% and 93.4% for MCV calculation. The latter test was found to be slightly more accurate than the OFT in predicting the presence of the alpha-thalassemia 1 and/or beta-thalassemia trait.

CONCLUSION

Both tests have high screening sensitivity for the alpha-thalassemia 1 and/or beta-thalassemia traits, and their simplicity and very low cost make them attractive as screening tests for large populations. Since MCV seems to provide fewer false-positive results, it may be the first choice wherever an automated hematology analyzer calculating MCV is available.

Cost-effectiveness of prenatal screening for thalassaemia in Hong Kong

OBJECTIVES

To determine the cost effectiveness of a universal prenatal screening program for alpha- and beta-thalassaemia.

METHODS

We retrospectively reviewed our program from 1998 to 2002, and calculated the direct and indirect costs of various components.

RESULTS

18,936 women were screened at our prenatal clinic and 153 couples were subsequently referred to our Prenatal Diagnostic Centre for counselling and further investigations. In addition, there were 238 tertiary referrals and 157 self-referrals. After investigations, 84 fetuses were at risk of beta-thalassaemia major/beta-E thalassaemia, 19 of them were affected and 18 were aborted. The total expenditure on our program (HK 10.0 million dollars) would be less than the postnatal service costs (HK 40.4 million dollars) for 18beta-thalassaemia major fetuses if they were born. Of 361 women at risk of carrying a homozygous alpha0-thalassaemia fetus, 311 (86.2%) opted for the indirect approach (using serial ultrasound examinations to exclude Hb Bart's disease), and 76 (24.5%) subsequently underwent an invasive test for a definitive diagnosis. The sensitivity and false positive rate of this indirect approach was 100.0% and 2.9% respectively.

CONCLUSION

It is cost effective to run a universal prenatal screening program in an area where both beta-thalassaemia and alpha-thalassaemia are prevalent. The indirect approach can effectively avoid an invasive test in unaffected pregnancies.

Liver disease in transfusion dependent thalassaemia major

AIMS

To study the prevalence and severity of liver diseases of transfusion dependent thalassaemia major patients, and correlate the histological and biochemical changes of iron overload in liver with the peripheral blood markers.

METHOD

Liver biopsy was performed to assess the histological changes and liver iron content (LIC).

RESULTS

One hundred patients were evaluated (median age 11.7 years, range 1.5-27). A total of 81 liver biopsies were performed in 73 patients; 43 samples were analysed for LIC. Grade 3-4 haemosiderosis and hepatic fibrosis was found in 44% and 30% of patients respectively; both were significantly associated with higher serum ferritin, liver enzymes, and LIC. Very high LIC (>15 mg/g dry weight) was present in 16.3% of patients.

CONCLUSION

Severe haemosiderosis and hepatic fibrosis were common in patients with thalassaemia major despite the use of chelation therapy. Liver biopsy provided information on fibrosis and LIC which could not be accurately predicted from peripheral blood markers.

Ten years' experience of antenatal mean corpuscular volume screening and prenatal diagnosis for thalassaemias in Hong Kong

OBJECTIVE

To determine the prevalence of thalassaemia carriers in Hong Kong.

SUBJECTS AND METHODS

From 1988 to 1997, 25,834 (53.7%) of 48,089 mothers were screened for thalassaemias by mean corpuscular volume (MCV) at the first antenatal visit.

RESULTS

In the screened population of 25,834, 2229 (8.6%) had MCV < or = 75 fl. Of these, 1121 (4.3%) were alpha-thal, 715 (2.8%) were beta-thal, 23 (0.1%) were alpha beta-thal, 57 (0.2%) were other haemoglobin variants, and 281 (1.1%) had either iron deficiency or uncertain causes. Out of 200 pregnancies at risk for homozygous alpha-thal-1 and 32 at risk for beta-thal major, 27 homozygous alpha-thal-1 and 7 beta-thal major were identified, compared favourably with the expected figures of 23 and 9.

CONCLUSION

Antenatal screening for thalassaemias by MCV is simple, effective and reliable. Universal screening has a different impact as bone marrow or cord blood stem cell transplant provides cure for beta-thal major. At risk couples have, as an alternative to termination of pregnancy, the option of early detection and treatment for their affected newborns or fetuses.

Prevention of beta-thalassemia major by antenatal screening in Hong Kong

The thalassemias are common in Hong Kong. One of the severe forms, beta-thalassemia major, has been preventable locally by antenatal screening since 1983. Yet new patients are still being diagnosed. In this retrospective study, 34 children with severe beta-thalassemia syndromes were diagnosed in two major public hospitals between 1990 and 1996. They included one pair of identical twins and two pairs of siblings. Twenty-seven (79%) had homozygous beta-thalassemia and seven (21%) had beta E thalassemia. All but four (12%) were transfusion dependent. Fifty-five (89%) parents had been evaluated for their thalassemia status. Forty-eight had beta-thalassemia traits and seven were hemoglobin E carriers. The reasons for the birth of these children with severe beta-thalassemia syndromes were (1) late or no antenatal visit (n = 8, 24.2%), including three cross-border deliveries in which the pregnant mothers came from mainland China to Hong Kong for confinement, (2) lack of maternal screening (n = 13, 39.4%), (3) lack of paternal screening (n = 7, 21.2%), (4) parental refusal (n = 3, 9.1%), and (5) unknown (n = 2, 6.1%). These findings suggest that several factors undermine the effectiveness of antenatal screening for prevention of thalassemias. Many medical practitioners and the general public are still not aware of the screening procedures. The migration of population from mainland China to Hong Kong may result in the birth of many more children with beta-thalassemia major.

Prevalence and genotypes of alpha- and beta-thalassemia carriers in Hong Kong -- implications for population screening

BACKGROUND

The thalassemias are common in southern China. We determined the prevalence of heterozygous carriers of these genetic disorders in Hong Kong and assessed the feasibility of a community-based screening program.

METHODS

An educational and screening program for the thalassemias was carried out in three high schools with a total of 2420 students. Seventy-five percent of the students agreed to undergo screening, which consisted of blood counts, hemoglobin electrophoresis, serum ferritin measurements, and DNA analyses.

RESULTS

Of the 1800 blood samples tested, 150 (8.3 percent) had microcytosis (mean corpuscular volume, <80 microm3). Ninety students (5.0 percent) were carriers of alpha-thalassemia, of whom 81 (4.5 percent) were carriers of the Southeast Asian type of deletion, in which both alpha-globin genes on the same chromosome 16 are deleted. Sixty-one students (3.4 percent) were carriers of either beta-thalassemia or the mutation coding for hemoglobin E. Six students were carriers of both alpha- and beta-thalassemias. On the basis of these figures, the estimated numbers of pregnancies in Hong Kong in which the fetus is at risk for homozygous alpha-thalassemia and beta-thalassemia major or intermedia are 145 and 80 per year, respectively. In Hong Kong the actual numbers of women referred for prenatal diagnoses of these disorders are approximately 95 and 40 per year, respectively.

CONCLUSIONS

Despite the availability of hospital-based screening and prenatal diagnosis for many years in Hong Kong, many women carrying fetuses at risk for thalassemia are not referred for genetic counseling. A community-based program of education, screening, and counseling is needed in Hong Kong and southern China.

Periosteal Gaucher-like cells in beta-thalassemia major

A 24-year-old Chinese woman who has undergone staged surgery for craniofacial deformity secondary to beta-thalassemia major is presented. Local clusters of Gaucher-like cells were found in the periosteum of the mandible. The histologic and ultrastructural features of these cells are described and the pathogenesis and differential diagnoses discussed. To the best of our knowledge, this is the first reported case of Gaucher-like cells occurring outside the lymphohematopoietic system in thalassemic patients.

Use of recombinant erythropoietin in thalassemic patients on dialysis

We studied the therapeutic benefit of recombinant human erythropoietin (rHuEPO) in dialysis patients with thalassemia minor. Four of the 40 randomly selected patients (22 on hemodialysis [HD], 18 on continuous ambulatory peritoneal dialysis [CAPD]) were identified to be thalassemic prior to a trial of rHuEPO (alpha-thalassemia trait in three and beta-thalassemia minor in one). All patients were initially treated with rHuEPO at a dose of 100 +/- 25 U/kg/wk subcutaneously depending on the hemoglobin level. EPO injections were continued for 16 weeks with further adjustments of the doses according to the hemoglobin level increases attained. All nonthalassemic patients reached a target hemoglobin of 10 g/dL at week 16, with an average maintenance dose of 120 +/- 7.8 U/kg/wk, but the hemoglobin was increased by only 1 g/dL in the thalassemic patients receiving 175 U/kg/wk. Following cessation of rHuEPO therapy for 6 weeks, all four thalassemic patients and 18 randomly selected nonthalassemic patients received a fixed dose of rHuEPO 4,000 U/wk (equivalent to 80 U/kg/wk) for 16 weeks. The hemoglobin remained unchanged in the thalassemic patients, but a progressive and significant increase of hemoglobin was observed in the nonthalassemic patients. At the last phase of the study, the thalassemic patients received rHuEPO at a dose of 100 or 125 U/kg/wk with 4-weekly increments of 25 U/kg/wk until their hemoglobin reached 10 g/dL. One patient developed uncontrolled hypertension with a dose of 150 U/kg/wk, and one reached the target hemoglobin at a dose of 200 U/kg/wk.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaemia and thalassaemia in healthy adolescents from southern Chinese families

A study was conducted on 447 healthy high school students of southern Chinese descent to determine the prevalence of anaemia and thalassaemia. Haematological data and serum ferritin levels were determined on all venous blood samples. Haemoglobin (Hb) electrophoretic study was conducted on 43 students who had anaemia (Hb less than 12 g/dL), and/or mean corpuscular volume (MCV) less than 80 fL. They were re-assessed after 1 month of oral iron therapy. Three girls had definite iron deficient anaemia (less than 1%). Thirty-nine students had either alpha, or beta-thalassaemia, only seven of whom showed anaemia. Since the overwhelming majority of both the thalassaemic students (38 of 39) and the participants (429 of 447) were of Cantonese extraction (native of Guangdong province), the overall incidence of 8.8% (alpha-thalassaemia 5.4%, beta-thalassaemia 3.4%) reflected the high frequency of the thalassaemia gene among this group of southern Chinese. MCV measurement, rather than Hb, was more useful in its detection.

Prenatal diagnosis of alpha and beta thalassemias and hemophilia A: experience in Hong Kong

Methods and strategies are described for the prenatal diagnosis of three common congenital disorders--alpha and beta thalassemias and hemophilia A. It is important to study the frequency of restriction fragment length polymorphisms and types of molecular defects in specific ethnic groups, since they are known to differ significantly. The studies reported here were carried out in southern Chinese who form the majority of the Hong Kong population. The information obtained is also useful for prenatal diagnosis in southern Chinese migrant populations in Canada, USA, Australia, UK and southeast Asia.

Beta-thalassemia problems in the Turkish population in the F.R.G

A sample of 165 normal Turkish probands (79 males, 86 females) living in the F.R.G. was screened for the presence of heterozygous beta-thalassemia as well as their knowledge and perception of thalassemias in general. Hematologic studies revealed two persons to be heterozygous for beta-thalassemia who had not known this before. This incidence of 1.2% in our sample of Turkish probands living in the F.R.G. is in accordance with the average range of 0.2-6% given by the World Health Organization for Turkey. The probands' places of origin in Turkey correlate well with the pattern of migration within the country, with most people coming from central Anatolia which is an area with a relatively low incidence of beta-thalassemia. Interviews conducted by a Turkish doctor revealed that the knowledge about thalassemias and the function of blood in general was extremely limited in our study population. On the other hand, 50% of the respondents would refrain from marriage or choose a different partner if both partners knew that they were heterozygous for thalassemia. 19% would still marry in this situation but refrain from having children. When asked about their most likely decision in the case of an early diagnosis of homozygous thalassemia, 78% said they would have a termination and only 15% would definitely go on with the pregnancy. About 65% felt that consanguineous marriage is a predisposing factor for diseases in the offspring. From our study it can be concluded that a large-scale screening program in the high-risk population which exists in most Mediterranean countries would be difficult regarding the more than one million people from Turkey living in the F.R.G. and would have to take into account the cultural and educational conditions of the Turkish minority. In general, if no Turkish-speaking specialist is available to explain the diagnostic possibilities, probably pre-pregnancy or early pregnancy testing would be the most appropriate way of reaching the couples at risk in the German medical system.

Congenital anemias in Macau

The implementation of a Primary Health Care system in Macau has created the need to study the prevalence of Congenital Anemias in the population to facilitate the planning of measures needed for their control. Blood samples from 3815 women attending the antenatal clinics were screened for beta-thalassemia using MCH values as the preliminary test, followed by quantitation of Hb A2 and Hb F. Isoelectric-focusing was used to screen 1091 cord blood samples for the presence of Hb Bart's. The prevalence of alpha- and beta-thalassemia carriers was found to be 6.2% and 3.6%, respectively.

Prenatal diagnosis of alpha- and beta-thalassemias: experience in Hong Kong

The incidence of alpha-thalassemia trait (alpha-thal-1 and alpha-thal-2) among Southern Chinese in Hong Kong is about 3%. From June 1983 to September 1987, prenatal diagnosis for homozygous alpha-thal-1 was performed in 88 pregnancies at risk, using direct DNA analysis of amniotic fluid cells or chorionic villi. Twenty-one homozygous alpha-thal-1 fetuses were aborted and confirmed as Hb Bart's hydrops fetalis, and two were "Hb H" hydrops fetalis. Of 47 pregnancies delivered, 26 were alpha-thal-1 heterozygotes, 10 normal, eight alpha-thal-1/normal. Twenty-one pregnancies, diagnosed as alpha-thal-1/normal, await delivery. Based on a 6% incidence of beta-thalassemia minor among pregnant women in Hong Kong, the number of pregnancies at risk for beta-thalassemia major should be 288 per annum. However, since February 1984, only 25 diagnoses were performed. Comprehensive screening and education programs need to be implemented. The majority of beta-thalassemia defects in Southern Chinese are point mutations, single nucleotide insertions or minor deletions, not detectable by standard gene mapping techniques. With linkage analysis of the defective gene to polymorphic restriction sites, a definitive diagnosis can be obtained in 50% of the families, while in the remaining there is a 50% exclusion rate. We routinely use the Hind III-3' beta, Bam HI-3' beta, Ava II-beta, and Hinc II-psi beta sites for linkage analysis. For first pregnancies, the marked linkage disequilibrium of the Bam HI polymorphism can be applied in 29% of the cases. In nonconclusive cases, fetal blood beta/gamma globin chain synthetic ratio was used.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of DNA polymorphisms for prenatal diagnosis of beta thalassemia in Chinese

Forty-seven Chinese suffering from beta thalassemia major and their parents were studied to establish linkage of the beta thal and beta A genes with 11 restriction site polymorphisms. There is marked linkage disequilibrium at the BamH I site 3' to the beta globin gene, such that, in 31% of pregnancies, absence of the site in the fetus can exclude beta thalassemia major. Using four restriction sites (Hinc II psi beta, Ava II beta, Hind III beta, and BamH I beta), prenatal diagnosis is feasible in all families. In 46% of all cases, a definitive diagnosis can be made, and in the remaining cases, a 50% chance of exclusion is possible. Fetal blood globin chain analysis would be required for the failures. Our experience in nine successive beta thalassemia prenatal diagnosis is also reported.