Mary Petrou

Method of sampling chorionic villi in first trimester of pregnancy under guidance of real time ultrasound.

Samples of chorionic villi were obtained in the first trimester by aspiration using a cannula passed transcervically under the guidance of real time ultrasound. In initial studies in 47 anaesthetised patients immediately before therapeutic abortion a method was developed giving a success rate of 89%. In 10 patients successful sampling was performed as an outpatient procedure without anaesthesia. In all, seven diagnostic procedures were undertaken and four of the five unaffected pregnancies continued. The technique of chorionic villous sampling using real time ultrasound is simple to learn and yields material for biochemical analysis and chromosomal study without the need for tissue culture. The exact obstetric risk, however, remains to be defined.

Informed choice in genetic screening for thalassaemia during pregnancy: audit from a national confidential inquiry.

Abstract Objective: National audit of informed choice in antenatal screening for thalassaemia. Design: Audit from the UK Confidential Enquiry into Counselling for Genetic Disorders. Setting: Thalassaemia module of the UK Confidential Enquiry into Counselling for Genetic Disorders. Subjects: 138 of 156 couples who had had a pregnancy affected by a major β thalassaemia from 1990 to 1994. Main outcome measures: How and when genetic risk was identified for each couple, and whether and when prenatal diagnosis was offered. Results: Risk was detected by screening before or during the first pregnancy in 49% (68/138) of couples and by diagnosis of an affected child in 28% (38/138) of couples. Prenatal diagnosis was offered in 69% (274/400) of pregnancies, ranging from 94% (122/130) for British Cypriots to 54% (80/149) for British Pakistanis and from 90% in the south east of England to 39% in the West Midlands. Uptake of prenatal diagnosis was 80% (216/274), ranging from 98% (117/120) among British Cypriots in either the first or second trimester to 73% (35/48) among British Pakistanis in the first trimester and 39% (11/28) in the second trimester. A demonstrable service failure occurred in 28% (110/400) of pregnancies, including 110 of 126 where prenatal diagnosis was not offered and 48 of 93 that ended with an affected liveborn infant. Conclusion: Although antenatal screening and counselling for haemoglobin disorders are standard practices in the United Kingdom, they are delivered inadequately and inequitably. An explicit national policy is needed, aiming to make prenatal diagnosis in the first trimester available to all couples and including ongoing national audit.

Prenatal diagnosis of beta‐thalassaemia in Pakistan: experience in a Muslim country

A service for prenatal diagnosis of β‐thalassaemia was introduced in Pakistan in May 1994. Two renowned Islamic scholars, consulted before the service was introduced, ruled that a pregnancy can be terminated if the fetus is affected by a serious genetic disorder, and if termination is before 120 days (17 weeks) of gestation. During the first 3½ years of the service 300 couples requested the test. Almost all the couples had been informed by their treating doctors. Most diagnoses were made between 10 and 16 weeks of gestation, and only 15 (5%) were reached after the 16th week. DNA analysis was by the amplification refractory mutation system (ARMS). A multiplex ARMS was developed in which three primer combinations identified the mutations in 91.5% of the couples. In 13 couples (4.3%) linkage analysis was required for the fetal diagnosis. In 47/53 (88.7%) women carrying an affected fetus the pregnancy was terminated. In six cases it was declined principally on religious grounds. Postnatal confirmation of the prenatal diagnosis was possible in 117 unaffected children. One year after the start of the service, interviews with 141 couples with an affected child showed that 72% knew of the availability of prenatal diagnosis. Thirty‐two of the informed couples had had a pregnancy, but only 18 (56%) used prenatal diagnosis. The main reasons for non‐utilization of prenatal diagnosis were the cost of the test and fear of undergoing the test, though some gave no clear explanation. This study demonstrates that prenatal diagnosis is feasible and acceptable in a Muslim country such as Pakistan. Copyright

EMQN Best Practice Guidelines for molecular and haematology methods for carrier identification and prenatal diagnosis of the haemoglobinopathies

Haemoglobinopathies constitute the commonest recessive monogenic disorders worldwide, and the treatment of affected individuals presents a substantial global disease burden. Carrier identification and prenatal diagnosis represent valuable procedures that identify couples at risk for having affected children, so that they can be offered options to have healthy offspring. Molecular diagnosis facilitates prenatal diagnosis and definitive diagnosis of carriers and patients (especially ‘atypical’ cases who often have complex genotype interactions). However, the haemoglobin disorders are unique among all genetic diseases in that identification of carriers is preferable by haematological (biochemical) tests rather than DNA analysis. These Best Practice guidelines offer an overview of recommended strategies and methods for carrier identification and prenatal diagnosis of haemoglobinopathies, and emphasize the importance of appropriately applying and interpreting haematological tests in supporting the optimum application and evaluation of globin gene DNA analysis.

Accuracy of prenatal diagnosis for haemoglobin disorders in the UK: 25 years' experience

We have reviewed the accuracy of prenatal diagnosis for the thalassaemias and sickle cell disorders performed for UK residents since the service began in 1974. Prenatal diagnosis has been performed in 3254 pregnancies: 517 by fetal blood analysis, 681 by Southern blotting and 2056 by polymerase chain reaction (PCR) methods, the majority using the amplification refractory mutation system (ARMS). The number of homozygotes diagnosed was 808 (24.8%). Twenty‐five diagnostic errors have been recorded, ten arising from non‐laboratory errors (0.31%) and 15 due to technical problems associated with the diagnostic techniques. The latter group consisted of eight misdiagnoses by globin chain synthesis (1.55%), five by Southern blot analysis (0.73%) and two by PCR methods (0.10%). The data show that the accuracy of prenatal diagnosis has improved with each development of diagnostic technique, and confirms that prenatal diagnosis of β‐thalassaemia and sickle cell disorders by ARMS‐PCR is very accurate and reliable. The overall error rate for prenatal diagnosis by PCR methods in the UK is now 0.41%. Copyright

Identification of novel Asian Indian and Japanese mutations causing β-thalassaemia in the Egyptian population

Abstractβ-thalassaemia is a major health problem in Egypt. It has been estimated that of the 1.5 million live births, 1000 children with β-thalassaemia major are born annually. Although the available treatment has increased the life expectancy of patients, it is still unsatisfactory and represents a significant drain on the country’s resources. National screening and prenatal diagnosis programmes can be provided in Egypt once the spectrum of β-thalassaemia mutations has been identified within the Egyptian population. We have examined 16 DNA samples with 21 β-thalassaemia mutations that remained unidentified in a study of 54 patients reported by Rady and colleagues in 1996. Using the polymerase chain reaction and single strand conformation analysis we identified the following changes: frameshift (FS) codon (CD) 8/9 (+G), 4 FS CD 29 (–G) and 2 novel mutations in exon I (15 CD 22 A-C and 1 FS CD 28 –C). In addition, a silent, probably polymorphic mutation, CD 17 G-A was present in all chromosomes.

Long‐term effect of prospective detection of high genetic risk on couples' reproductive life: data for thalassaemia

Prospective risk detection with availability of prenatal diagnosis is the best service currently available for couples at high genetic risk Here we describe the long term effect of this service on the reproductive life of 102 couples at risk of thalassaemia, whose risk was detected prospectively by carrier screening, who made use of prenatal diagnosis, and where the woman is now over 40. Overall outcome for couples is described in terms of number of favourable versus unfavourable pregnancy outcomes. (A favourable pregnancy outcome = unaffected livebirth, or affected livebirth resulting from informed parental choice.) The 102 couples had a total of 356 pregnancies, including 302 viable pregnancies, and 88% achieved a family unburdened by thalassaemia. 68% of viable pregnancies had a favourable outcome, but only 43% of couples had only favourable outcomes, and 26% lost two or more viable wanted pregnancies. When early losses are included 58% of pregnancies had a favourable outcome, but only 30% of couples had only favourable outcomes, and 41% lost two or more pregnancies. Even with the best available service, at risk couples remain victims of chance, and a significant minority experience great difficulty in obtaining even one healthy child. Research is needed on approaches that may allow couples better control of reproductive outcomes. Copyright

A different molecular pattern of beta-thalassemia mutations in northeast Brazil

The main hereditary hemoglobin (Hb) disorders of clinical significance in Brazil are sickle cell disease and β‐thalassemia (thal). The sickle gene was introduced by the slave trade, whereas β‐thal was introduced later, due to a massive immigration (mostly by Italians) between 1870 and 1953, mainly to the southeast region of Brazil. Molecular studies performed in the southeast of the country showed a marked prevalence of the nonsense mutation at codon 39 (C → T) (47–54%), leading to severe forms of β0‐thal. However, the northeast region of the country has a different demographic history, characterized by the absence of the massive Italian immigration. Owing to this and since the majority of cases of β‐thal in Pernambuco, a state located in the northeast of the country, have mild or intermediate clinical and laboratory features, we would predict a different spectrum of β‐thal mutations in this region. We examined 60 unrelated patients (86 β‐thal chromosomes) under regular clinical follow‐up in Pernambuco: 6 were regularly transfused β‐thal major subjects, 20 had β‐thal intermedia, 20 had Hb S/β‐thal and 14 were β‐thal trait individuals. The following mutations were found: IVS‐I‐6 (T → C) 62.8%, IVS‐I‐1 (G → A) 15.1%, IVS‐I‐5 (G → C) 9.3%, IVS‐I‐110 (G → A) 8.2%, codon 39 (C → T) 3.5%, and codon 30 (AGG → AGC) 1.1%. These data show different patterns of β‐thal mutations in two regions of Brazil, demonstrating a thus far unrevealed heterogeneity of the disease in the country.

ANTENATAL DIAGNOSIS - HOW TO DELIVER A COMPREHENSIVE SERVICE IN THE UNITED-KINGDOM

FIGURE. 1, which summarizes the aims of genetic screening and prenatal diagnosis, shows that the main objective is informed choice for couples at risk. To allow choicc, one must offer screening and genetic counseling. Prenatal diagnosis is the approach chosen by most informed couples at risk of a severe genetic disorder. Divorce is not a common solution, and artificial insemination by donor is not popular. In the United Kingdom, in principle, screening for hemoglobinopathy carriers, counseling, and prenatal diagnosis (by fetal blood sampling or chorionic villus sampling [CVS] and DNA analysis) is available to the whole population within the National Health Service. Our objective is to ensure that all couples at risk for having children with a hemoglobin disorder have the opportunity of informed choice. It is becoming increasingly clear that an outreach approach, including quality control, is needed to ensure that the service is delivered equitably to everyone who needs it. Scrvicc monitoring in the Mediterranean region has shown for thalassemia that a comprehensive “control” programd can lead to near-eradication of the disease’,* (FIG. 2). For sickle cell disease we would expect a smaller reduction in the birth rate, since only 50% of counseled couples request prenatal diagnosi~.’.~ In the United Kingdom, 6.5% of the population and about 10% of the births are in ethnic minority groups at risk for hemoglobinopathies. Thalassemias are carricd by 3-17% of people of Mediterranean or Asian origin, and a sickle trait is carried by

Prenatal detection of Hb mutations using transcervical cells

Prenatal diagnoses were performed on six selected pairs of parents known to be carriers of Hb mutations by testing transcervical cells (TCCs) retrieved, prior to chorionic villus sampling (CVS), by aspiration of the cervical mucus from the pregnant mothers at 10–12 weeks of gestation. A concordance between the results of testing chorionic villus cells and isolated clumps of trophoblastic cellular elements was observed in four of the six cases.