Abstract:

Objective Quartile method and discriminant analysis method were used to establish cut-off value of congenital adrenal hyperplasia(CAH) screening, expecting to increase screening accuracy.Methods Newborn CAH screening data were retrospective investigated from Jun. 2012 to Jun. 2015 in Guangxi Province. 17-OHP≥30 nmol·L-1 was considered as suspected positive case. Quartile method was used according to different gestation age(＜28， -32，-36 and ≥37 weeks) to establish 17-OHP cut-off (P99) respectively. Unstandardized Fisher analysis was used to establish cut-off according to gestation age, birth weight and 17-OHP level. Recalling the suspected positive cases, after thorough clinical test, highly suspected case was performed for gene test(gold standard). Two methods were compared with gold standard respectively to calculate sensitivity and specificity of CAH diagnosis.Results In all 215 900 newborns, 1 110 were suspected positive(positive rate 0.51%), 994 were recalled(recall rate 89.6%). ①17-OHP cut-off (P99) of ＜28， -32，-36 and ≥37 weeks was 236.0、113.7、50.0 and 29.0 nmol·L-1 respectively, which was decreased as gestation age growng. These new cut-offs were used to recalculate the screening result, 547 cases were positive (including 50 cases with 17-OHP<30 nmol·L-1), while 613 former positive cases turned to negative(55.2%).②The discriminant equation was Z= (-0.207·gestation age)+ (-0.000242·birth weight)+ 0.54·17-OHP level+ 8.25, cut-off was 24.24. Using this cut-off, 439 were positive, while 671 turned to negative. ③Using these two methods together could figure out 291 positive(0.13%) cases and 819 turned to negative. ④965 recalled positive cases could be excluded by clinical test, the rest 29 cases were performed for gene test, while 12 of them were diagnosed as CAH. Quartile method, discriminant analysis method and combination of the two methods compared with gold standard, sensitivity was 100%, specificity was 5.9%, 11.8% and 17.7% respectively.Conclusion Both quartile method and discriminant analysis method can increase screening accuracy. Using these two methods together is even better in screening.