High facial specificity and positive predictive value are required to diagnose fetal alcohol syndrome when prenatal alcohol exposure is unknown.

Abstract

Background: Facial criteria with high specificity and positive predictive value (PPV) to prenatal alcohol exposure (PAE) are required to diagnose fetal alcohol syndrome (FAS) when documentation of PAE is unavailable. Not all fetal alcohol spectrum disorder (FASD) diagnostic guidelines appear to meet these criteria.

Methods: A dataset generated from a 10-year FAS screening of 1,602 children in fostercare conducted by the University of Washington FAS Diagnostic & Prevention Network was used to determine how well the FAS facial phenotype, microcephaly and growth deficiency (individually and in combination at varying levels of magnitude) predicted PAE.

Results: The 4-Digit-Code Rank 4 FAS facial phenotype was the only outcome that provided sufficient PPV and specificity to PAE (100%) to allow the facial phenotype to serve as confirmation of PAE in a diagnostic setting when PAE is unknown. Even minimal relaxation of the phenotype (e.g., Face Rank 3) resulted in PPV (35%) and specificity (88.7%) values too low to use as confirmation of PAE. Further relaxation of the facial criteria, as defined by the Hoyme et al., 2016 FASD guidelines, resulted in even lower PPV (17.9%) and specificity (76.6%); both too low to serve as confirmation of PAE in a diagnostic setting. The presence of all three physical features of FAS (Hoyme et al FAS facial phenotype, growth and OFC ≤10^th percentile) did not increase PPV beyond chance (52%).

Conclusions: FASD diagnostic guidelines that use relaxed criteria for the FAS facial phenotype risk misdiagnosing and over-diagnosing FAS and partial FAS when PAE is unknown.