Parental serum alkaline phosphatase activity as an auxiliary tool for prenatal diagnosis of hypophosphatasia

OBJECTIVE: The objective of this study is to clarify the usefulness of parental alkaline phosphatase (ALP) for prenatal diagnosis of hypophosphatasia (HPP). METHODS: Maternal (m) and paternal (p) ALP values were measured in 77 cases from a multicenter cohort (fetal skeletal dysplasia forum in Japan) of cases with short limbs on ultrasonography during pregnancy. After birth, X-rays, cord blood ALP, and gene analysis were evaluated to achieve an exact diagnosis. The screening usefulness of ALP was examined retrospectively. RESULTS: Seventeen cases were eventually diagnosed as HPP and 60 as not HPP; the overall mean m-ALP and p-ALP (standard deviation) values were 133.4 (53) versus 197 (69) IU/L and 149.6 (71.8) versus 231 (61.4) IU/L (p < 0.001). Receiver operating characteristic curve analysis showed that the optimal m-ALP and p-ALP cutoff values were 123 and 165 IU/L, respectively. Presence of at least one of the m-ALP or p-ALP values abnormally low had a sensitivity, specificity, and positive predictive values of 82% (14/17), 93%, and 78%, respectively, for the diagnosis of HPP. CONCLUSION: Parental ALP measurement might be an auxiliary tool to hone in the prenatal diagnosis of fetal HPP. © 2017 John Wiley & Sons, Ltd.