Components of an effective large scale program for the prevention of inherited hemoglobin disorders; the paradigm of Greece

Abstract

Large scale prevention programs for Thalassemia major or Sickle cell disease have already been set up in several places with high frequency of the deleterious genes. The Greek health authorities realized the magnitude of the problem and allowed the creation of a National Thalassemia Center in 1972. The incidence of thalassemia in Greece varies from 1-2 per cent up to 15%, the mean being around 8 per cent. With an annual number of births around 100,000, if no prevention measures are taken, the expected yearly number of newborns with thalassemia major in Greece should be of the order of 100-120. To these one should add a few decades of sickle cell patients, homozygotes or compound HbS/β-thalassemia heterozygotes. The total number of patients with thalassemia major now surviving is estimated at 4,000 plus another 600-800 patients with sickle cell disease. The National Thalassemia Center Center defined a network of peripheral Thalassemia Units in the major regional hospitals of the country, let them provide free carrier identification to couples requesting the test. When both partners were identified as carriers, they were given preliminary information locally and were referred to the Central Laboratory in Athens for further genetic counselling and, if so decided, prenatal diagnosis. Prenatal diagnosis was provided initially by fetoscopy and fetal blood biosynthesis; this approach was soon replaced by chorionic villi sampling and molecular techniques. The number of prenatal diagnoses carried out yearly over the last decade appears to cover the needs; the number of positive diagnoses is very close to the expected 25%, which also excludes overdiagnosis. The overall evaluation of the the program is reflected in the number of infants who were admitted to the pediatric clinics of the country in need of transfusion over the years the program was functioning. In fact, over the past years this number has steadily decreased to approximately 10 missed diagnoses annually, but has not reached zero as expected, after all this effort. The function of a comprehensive program for the prevention of thalassemia and HbS disease in Greece over the last 25 years has helped enormously in (a) avoiding birth of several hundreds of children with thalassemia major, thus (b) securing the use of the available resources for the optimal care of the patients who are living to-day, and (c) allowing thousands of couples at risk to give birth to healthy children. 很多地方都已开展了针对地中海贫血或镰状细胞贫血的大型预防方案，病变基因的频率很高。 希腊健康机构意识到了此问题的严重性，在1972年，同意创建了国家地中海贫血防控中心。希腊人患地中海贫血的几率从百分之一、二至百分之十五不等，平均值为百分之八左右。 按照年均人口出生率100，000计算，如果不采取任何防控措施，希腊每年新生儿中，预计有100至120名新生儿会患上地中海贫血。对于这些患儿来说，应给镰状细胞贫血患者加上数十年的纯合子或复合性HbS/β-地中海贫血杂合子。 重型地中海贫血现在的生存患者总数估计在4,000多名，其中有600至800名患者为镰状细胞贫血。 国家地中海贫血防控中心规定国家的主要地区医院的地中海贫血部门都应有对外网络，为要求测试的夫妇提供地贫基因携带者免费鉴定。 如果夫妇双方均被鉴定为地贫基因携带者，他们会被在本地给予事前资料，并会被安排到位于雅典的中心实验室进行进一步遗传咨询以及作出决定之后的产前检查。 以前，采用胎儿镜窥察和胎儿血液生物合成来进行产前检查，此方法不久之后便不再使用，取而代之的是绒毛标本采样和分子技术。 在过去的十年间，每年产前检查的数量几乎都满足了需求，诊断结果为阳性的产前检查数量接近预计的25%，不包括过度诊断。 此方案的总体评估在那些去国家幼儿科诊所的婴幼儿数量上反映了出来，这些婴幼儿需要常年输血，此时这项方案发挥了它的作用。 事实上近几年来，这项数字已稳定地下降了，因为每年约有10个误诊病例，然而在经过一系列努力之后， 仍未达到零的期望值，在希腊过去的25年中，为防止地中海贫血和HbS疾病的所实施的广泛的方案发挥了如下作用：（1）已帮助预防了数量众多数以千计的儿童患上重型地中海贫血；（2）为活着的患者提供最好的照顾而对可用资源的使用进行保护；（3）使上千对本来濒临危险的夫妇生下健康孩子。

Keywords

• inherited hemoglobin disorders, prevention.