Résumé
Objective:To analyze the costs and effectiveness of five common screening modes and genetic screening for thalassemia in China in order to find the optimal way and provide evidence for the implementation of thalassemia prevention and control projects in Hunan Province.Methods:From June 2020 to April 2021, 12 971 couples from 14 cities and autonomous prefectures in Hunan Province were selected as the study population. The diagnosis of thalassemia was based on the results of genetic testing. Results of routine blood test and hemoglobin electrophoresis were collected and analyzed. The efficacy of five screening modes, at the cut-off value of <80 fl or 82 fl for the mean corpuscular volume (MCV), was analyzed by positive predictive value, negative predictive value, Jorden index and cost-effectiveness ratio. Sensitivity analysis was used to assess the feasibility of genetic screening at different costs after fixing the costs of routine blood and hemoglobin electrophoresis. The five thalassemia screening models are as follows: Mode 1: The woman had a blood routine test first. If the result was positive, the spouse required a blood routine test. If both results were positive, a thalassemia gene test should be offered to the couple. Mode 2: Both husband and wife were screened by blood routine and hemoglobin electrophoresis. If one or both of them were positive, both would be tested for thalassemia gene. Mode 3: The couple received blood routine tests initially. If either was positive, both should receive hemoglobin electrophoresis testing. If either was positive, both parties will conduct thalassemia gene testing. Mode 4: The woman was screened by blood routine and hemoglobin electrophoresis. If any one of them was positive, the woman would be tested for thalassemia gene. If the gene test result was positive, the spouse should receive thalassemia gene. Mode 5: Both spouses conducted a blood routine test. If either was positive, both would conduct hemoglobin electrophoresis test. If both were positive, both spouses should receive thalassemia gene testing. Gene testing mode: The woman would be tested for thalassemia, and her spouse would have thalassemia test too if her result was positive.Results:When using MCV<80 fl as the cut-off for diagnosing thalassemia, the Youden indices of the five prenatal screening modes in Hunan Province were 0.551, 0.639, 0.898, 0.555 and 0.356, while when using MCV<82 fl as the cut-off, the Youden indices were 0.549, 0.629, 0.851, 0.548 and 0.356. When the MCV cut-off value was <80 fl, the missed diagnosis rates of the five screening modes were 44.44%, 0.00, 0.00, 18.52% and 62.96%, and the cost-effectiveness ratios were 21 709, 250 939, 76 870, 138 463 and 92 860 yuan (RMB)/couple, respectively. When the price of genetic testing was lower than 55 yuan (RMB), the cost-effectiveness ratio of genetic screening was lower than that of Mode 3.Conclusions:MCV<80 fl can be considered as the positive criteria in blood routine screening for thalassemia in Hunan Province, and the cost-effectiveness ratio of Mode 3 (the couple received blood routine tests initially. If either was positive, both should receive hemoglobin electrophoresis testing. If either was positive, both parties will conduct thalassemia gene testing) is the best. Genetic screening has certain advantages with the decreasing price.
Résumé
<p><b>OBJECTIVE</b>To summarize the molecular epidemiology of hemoglobinopathies in Yongzhou area of Hunan province in order to provide a basis for making the guidelines of local thalassemia prevention program.</p><p><b>METHODS</b>Two thousand and two samples (1001 couples) were randomly recruited based on demographic data and distribution of ethnic groups. All samples were subjected to full blood count and analysis of hemoglobin and 6 common alpha-thalassemia mutations. Known beta-thalassemia mutations were screened in samples with beta-thalassemia trait. The remaining samples with positive phenotype and unknown mutations were subjected to DNA sequence analysis.</p><p><b>RESULTS</b>Two hundred and forty individuals were found to be carriers of hemoglobinopathic mutations, which included 6 common alpha-thalassemia deletions, 9 common beta-thalassemia mutations and 3 common structural hemoglobin variants. One hundred and seventy-four mutant alleles for alpha-thalassemia were detected, which gave a carrier rate of 8.69%, of which 0.1% was due to HbH disease. Seventy mutant alleles for beta-thalassemia were detected, which gave a carrier rate of 3.50%. Seven subjects (0.35%) were identified as carriers of hemoglobin variants. The overall carrier rate for hemoglobinopathic mutations was 12.54% based on detection of 251 hemoglobinopathy mutant alleles. The overall carrier rate for alpha- and beta-thalassemia among ethnic Yaos was 25.00%, which was significantly higher than that of ethnic Han Chinese (11.14%, P< 0.01).</p><p><b>CONCLUSION</b>The prevalence and mutation spectrum of hemoglobinopathies in Yongzhou area has been delineated for the first time.</p>