LactaseLactose IntoleranceLactase-Phlorizin HydrolaseDisaccharidasesLactose Tolerance TestEndoscopes, GastrointestinalSucrasebeta-GalactosidaseJejunumFinlandMilkGenotypePolymorphism, Single NucleotidePolymerase Chain ReactionDelayed DiagnosisPrenatal DiagnosisEarly DiagnosisSensitivity and SpecificityDiagnosisRetrospective StudiesDiagnostic Errors