Results of citrullinemia and carnitine uptake defects screening. The study population included 46,699 newborns screened for citrullinemia (A) and 30,237 for carnitine uptake defects (B). (A) A total of 314 newborns were enrolled in the second-tier screening due to abnormal (but below the diagnostic cutoff) concentrations of total galactose, methionine, tyrosine, or citrulline in the initial dried blood spots. Gal: abnormal galactosemia screening results; AA: abnormal homocystinuria or tyrosinemia screening results; He: heterozygotes for citrin mutations. (B) A total of 210 newborns were enrolled in the second-tier screening due to low free carnitine concentration; among these, 4 exceeded the diagnostic cutoff. CUD: carnitine uptake defects; He: heterozygotes for p.R254X mutation.