[Comparison of the effect of three β-thalassemia prenatal screening strategies using in Guangdong province].

OBJECTIVE

To compare the effect of three β-thalassemia prenatal screening strategies in Guangdong province.

METHODS

A total of 13 284 hospital-delivered couples and 13 369 newborns were recruited from 91 hospitals in 21 counties or districts of Guangdong province from June to December 2012. Mean cell volume (MCV), mean corpuscular hemoglobin (MCH) and hemoglobin A2 (Hb A2) were tested for all the couples, and all the couples and newborns were detected by 17 types of β-globin gene mutations. The effect of three β-thalassemia prenatal screening strategies were compared as following: (1) MCV/MCH with Hb A2 serial screening (SS): Hb A2 was tested if the woman's MCV < 82 fl and (or) MCH < 27 pg. If the woman's Hb A2 > 3.5, it meant positive. And if the woman was β-thalassemia carrier and her husband's Hb A2 > 3.5, it meant couple positive. (2) MCV/MCH with Hb A2 parallel screening (PS): if the woman's MCV < 82 fl and (or) MCH < 27 pg and (or) Hb A2 > 3.5 pg, it meant couple positive. And the husband would be tested for β-globin gene mutations if the woman was β-thalassemia carrier. (3) MCV/MCH with Hb A2 serial screening for couples (SSC): if one of the couple or both of them had MCV < 82 fl and (or) MCH < 27 pg, the couple would be tested for Hb A2, and if one of the couple got Hb A2 > 3.5, it meant couple positive.

RESULTS

(1) For the SS strategy, the sensitivity was 92.69% (583/629); the specificity was 99.87% (12 638/12 655); the positive predictive value was 97.17% (583/600); and the negative predictive value was 99.64% (12 638/12 684). The results of β-globin gene mutations tested showed that the rate of β-thalassemia carriers was 4.74% (629/13 284) in the 13 284 pregnant women, and it was 4.29% (570/13 284) in their husbands. (2) The SS strategy detected 27 (0.20%, 27/13 284) β-thalassemia carrier couples. For the SS strategy detecting β-thalassemia carrier couples, the missed diagnosis rate was 11.11% (3/27); the sensitivity was 88.89% (24/27); the specificity was 100.00% (27/27); the positive predictive value was 100.00% (24/24); and the negative predictive value was 99.98% (13 257/13 260). (3) When using the SS strategy for 13 369 offsprings, there were 582 β-thalassemia carriers (4.35%, 582/13369), including 578 (99.31%, 578/582) minor β-thalassemia, 3 (0.52%, 3/582) intermedia β-thalassemia and 1 (0.17%, 1/582) major β-thalassemia. The SS strategy detected 25 fetuses who needed β-thalassemia prenatal diagnosis. (4) For the PS strategy, the sensitivity was 98.09% (617/629); the specificity was 88.73% (11 229/12 655); the positive predictive value was 30.20% (617/2 043); and the negative predictive value was 99.89% (11 229/11 241). (5) When using the PS strategy for the β-thalassemia carrier couples, the sensitivity was 100.00% (27/27); the specificity was 95.55% (12 667/13 257); the positive predictive value was 4.38% (27/617); and the negative predictive value was 100.0% (12 667/12 667). (6) The PS strategy detected 28 fetuses who needed β-thalassemia prenatal diagnosis in 13 369 offsprings. (7) For the SSC strategy, the sensitivity was 93.80% (590/629); the specificity was 95.75% (12 117/12 655); the positive predictive value was 52.30% (590/1 128); and the negative predictive value was 99.68% (12 117/12 156). When the SSC strategy was used for the husbands, the sensitivity was 92.28% (526/570); the specificity was 95.27% (12 112/12 714);the positive predictive value was 46.63% (526/1 128); and the negative predictive value was 99.64% (12 112/12 156). (8) When the SSC strategy was used in β-thalassemia carrier couples, the sensitivity was 100.00% (27/27); the specificity was 91.69% (12 156/13 257); the positive predictive value was 2.39% (27/1 128); and the negative predictive value was 100.00% (12 156/12 156). (9) The SSC strategy detected 28 fetuses who needed β-thalassemia prenatal diagnosis.

CONCLUSIONS

All the three β-thalassemia prenatal screening strategies had good effect in clinical practice and public health. While in the high-prone area of β-thalassemia, MCV/MCH with Hb A2 parallel screening and MCV/MCH with Hb A2 serial screening for couples stratigies were better.