Table 4 Summary of all treatable IEMs (n = 38, 57%) that can be detected by ‘1 ^st -tier’ metabolic screening tests, which are affordable and accessible, with the potential to identify multiple IEMs

Acylcarnitine profiles (n = 3)

● MCAD deficiency

● SCAD deficiency

● VLCAD deficiency

Free-to-total serum/plasma carnitine (n = 1)

● Carnitine palmitoyltransferase I deficiency

Plasma Amino Acids (n = 10)

● Argininemia

● Hartnup disease

● MTHFR Deficiency (&tHcy)

● Argininosuccinate lyase deficiency

● HHH syndrome

● Ornithine transcarbamylase deficiency

● Citrullinemia type I

● Maple syrup urine disease

● Phenylketonuria (PKU)

● Citrullinemia, type II

Plasma cholesterol (n = 1)

● Cerebrotendinous xanthomatosis (CTX)

Serum copper & ceruloplasmin (n = 2)

● Menkes Disease (& urine deoxypyridinoline)

● Wilson Disease (& urine copper)

Urine tests

Urine creatine metabolites (n = 1)

● GAMT deficiency

Urine oligosaccharides (n = 1)

● Fucosidosis

Urine organic acids (n = 17)

● 3-Methylglutaconic aciduria type 1

● Ethylmalonic encephalopathy (& ACP)

● MHBD deficiency

● 3-Methylcrotonyl-CoA carboxylase (MCC) deficiency (& ACP)

● SSADH

● HMG-CoA lyase deficiency

● β-Ketothiolase deficiency

● Glutaric aciduria type I

● mHMG-CoA synthase deficiency

● Cobalamin deficiencies (& PAA)

● Holocarboxylase synthetase deficiency

● Multiple acyl-CoA-dehydrogenase deficiency (MADD)

● Cystathionine β-synthase deficiency

● Isovaleric academia

● Propionic academia

● Methylmalonic academia

● SCOT deficiency

Urine purines & pyrimidines (n = 2)

● Lesch-Nyhan syndrome

● Molybdenum cofactor deficiency