To investigate the diagnostic values of noninvasive prenatal testing (NIPT) combined with serum soluble transferrin receptor (sTfR), growth differentiation factor (GDF)-15, and red blood cell volume distribution coefficient of variation (RDW-CV) in pregnant women for diagnosis of fetal β-Thalassemia.

From January 2017 to June 2018, a total of 120 pregnant women whose fetuses were diagnosed as β-Thalassemia by amniocentesis in Zigong Maternal and Child Health Hospital were selected as research subjects. They were included into mild group (n=48), intermediate group (n=40) and severe group (n=32), respectively, according to mild, intermediate and severe β-Thalassemia of their fetuses. And other 100 cases healthy pregnant women who received routinely prenatally examination in the same hospital during the same period and with normal development of fetuses were selected as controls, and were included into control group. Fasting elbow venous blood was collected from 4 groups of fetal pregnant women, and fetal cell-free DNA (cfDNA) was collected from peripheral plasma of pregnant women. After amplification of cfDNA by twice PCR methods, fetal β-Thalassemia gene was detected by reverse dot blot hybridization. Enzyme-linked immunosorbent assay method was used to detect serum levels of sTfR, GDF-15 and RDW-CV of pregnant women in 4 groups. Serum levels of sTfR, GDF-15 and RDW-CV of pregnant women in 4 groups were compared by one-way ANOVA, and further multiple comparisons were performed by least significant difference (LSD)-t test. The sensitivity, specificity, crude accuracy, positive predictive value, and negative predictive value of combination of NIPT and serum sTfR, GDF-15 and RDW-CV levels of pregnant women, and detection of these four indicators alone for the diagnosis of fetal β-Thalassemia were calculated by comparison with " gold standard" of fetal β-Thalassemia. The procedures in this study were in line with the requirements of World Medical Association Declaration of Helsinki revised in 2013. There were no statistical differences in general clinical data such as fetal gestational age and age of pregnant women among four groups (P>0.05).

①Among 40 pregnant women who had the same genotype of β-Thalassemia with her husband, diagnosis accordance rate of NIPT and prenatal diagnosis amniocentesis for diagnosis of fetal β-Thalassemia was 90.0% (36/40). And among 80 pregnant women who had different β-Thalassemia genotype with her husband, diagnosis accordance rate of these two methods was 90.0% (72/80). ②The serum levels of sTfR, GDF-15, and RDW-CV of pregnant women in four groups were compared, and all the differences were statistically significant (F=2 283.445, 323.181, 45.900, Pall<0.001). Results of further multiple comparisons showed that there were statistically significant differences in serum levels of sTfR, GDF-15, and RDW-CV of pregnant women between each two groups (P<0.05), and serum levels of sTfR, GDF-15, and RDW-CV of pregnant women gradually increased with the increase of fetal β-Thalassemia severity. ③The sensitivity, specificity, crude accuracy, positive predictive value, and negative predictive value for diagnosis of fetal β-Thalassemia by NIPT combined with serum levels of sTfR, GDF-15, and RDW-CV of pregnant women were 86.7%, 88.0%, 87.3%, 86.7% and 84.6%, respectively. And its specificity and positive predictive value were significantly higher than those of serum sTfR, GDF-15, and RDW-CV levels detection alone in pregnant women, and all the differences were statistically significant (vs serum sTfR level detection in pregnant women: χ²=8.866, 5.301, P=0.003, 0.021; vs serum GDF-15 level detection in pregnant women: χ²=9.765, 5.929, P=0.002, 0.015; vs serum RDW-CV level detection in pregnant women: χ²=7.167, 4.327, P=0.007, 0.038).

Serum level of sTfR, GDF-15 and RDW-CV of pregnant women are expected to be the diagnostic markers of fetal β-Thalassemia. NIPT combined with detection of these three indicators can improve the specificity and positive predictive value for diagnosis of fetal β-Thalassemia. As the sample size in this study is relatively small, the diagnostic value of NIPT combined with serum levels of sTfR, GDF-15 and RDW-CV of pregnant women for fetal β-Thalassemia remains to be further studied and confirmed.