Bharti Omesh Kumar, Sood Rajesh Kumar, Sharma Hans Raj, Kaur Harsharan, Minhas Varinder, Chauhan Rajinder, Nigam Nitu, Phull Archana
State Institute of Health and Family Welfare, Shimla, Himachal Pradesh, India.
National Health Mission (NHM), Government of Himachal Pradesh, Shimla, Himachal Pradesh, India.
Asian J Transfus Sci. 2020 Jul-Dec;14(2):172-178. doi: 10.4103/ajts.AJTS_109_18. Epub 2020 Dec 19.
Himachal Pradesh is a hill state in North India in the Western Himalayas. β-thalassemia is a genetic disorder of hemoglobin inherited in an autosomal recessive manner that results in defective globin production leading to the early destruction of red blood cells. β-thalassemia has long been neglected in Himachal Pradesh due to popular belief that it runs along "Lahore-Gujarat-Punjab" belt in India. Therefore, there is no β-thalassemia testing facility currently in the state.
To estimate the prevalence of β-thalassemia carriers, we calculated the sample size based on probability proportional to size self-weighing design. In each of 20 selected colleges, 111 students having an age of 18-25 were tested for high-performance liquid chromatography (HPLC) and complete blood count. Some were further tested for the mutations. We computed sensitivity, specificity, positive predictive value (PPV) and negative predictive value, and receiver operating characteristic curve for mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) red cell parameters.
Of the 2220 students, 57 were found to be β-thalassemia carrier by HPLC. The overall prevalence rate was 2.6% which translates to probable 180,000 β-thalassemia carriers in Himachal Pradesh. Six districts bordering highly endemic Punjab had a higher prevalence. Hemoglobin D-Punjab, Heterozygous-Iran Trait, and raised fetal hemoglobin were found. Thalassemia major and sickle cell disease were not found. Anemic status or MCV/MCH parameters were not found to be reliable predictors of thalassemia carrier status among the healthy populations of HP. The predominant mutation found was IVS 1-5 G > C.
Popular ongoing strategy for screening with MCV and MCH has low-PPV and can miss upto 37% of true thalassemia carriers. HPLC is better strategy for screening carriers and reduces further spread of thalassemia.
喜马偕尔邦是印度北部喜马拉雅山脉西部的一个山区邦。β地中海贫血是一种以常染色体隐性方式遗传的血红蛋白遗传性疾病，会导致珠蛋白生成缺陷，进而导致红细胞过早破坏。由于普遍认为β地中海贫血在印度沿着“拉合尔-古吉拉特-旁遮普”地带传播，因此在喜马偕尔邦长期被忽视。所以，该邦目前没有β地中海贫血检测设施。
为了估计β地中海贫血携带者的患病率，我们根据规模自加权设计中与规模成比例的概率计算样本量。在20所选定的学院中，对每所学院的111名年龄在18至25岁之间的学生进行了高效液相色谱法（HPLC）检测和全血细胞计数。部分学生进一步进行了突变检测。我们计算了平均红细胞体积（MCV）和平均红细胞血红蛋白含量（MCH）这两个红细胞参数的敏感性、特异性、阳性预测值（PPV）和阴性预测值，以及受试者工作特征曲线。
在2220名学生中，通过HPLC检测发现57名学生为β地中海贫血携带者。总体患病率为2.6%，这意味着喜马偕尔邦可能有180000名β地中海贫血携带者。与高流行率的旁遮普邦接壤的六个地区患病率更高。发现了血红蛋白D-旁遮普型、杂合子-伊朗特征型以及胎儿血红蛋白升高的情况。未发现重型地中海贫血和镰状细胞病。在喜马偕尔邦的健康人群中，贫血状态或MCV/MCH参数并非β地中海贫血携带者状态的可靠预测指标。发现的主要突变是IVS 1-5 G > C。
目前常用的通过MCV和MCH进行筛查的策略PPV较低，可能会漏诊高达37%的真正地中海贫血携带者。HPLC是筛查携带者的更好策略，可减少地中海贫血的进一步传播。
