Newborn Population Screening for Classic Homocystinuria by Determination of Total Homocysteine from Guthrie Cards

ObjectiveTo allow early recognition of cystathionine β-synthase by newborn screening.Study designTotal homocysteine was determined in dried blood spots with a novel, robust high-performance liquid chromatography method with tandem mass spectrometry. Quantification of homocysteine was linear over a working range up to 50 μmol/L. For mutation analysis, DNA was tested for 2 mutations common in Qatar.ResultsBoth methods proved to be suitable for high throughput processing. In 2 years, 7 infants with classic homocystinuria were identified of 12 603 native Qatari infants, yielding an incidence of 1:1800. Molecular screening would have missed 1 patient homozygous for a mutation not previously identified in the Qatari population. Over a period of 3 years, a total of 14 cases of classic homocystinuria were detected by screening of homocysteine from all newborn infants born in Qatar (n = 46 406). Homocysteine was always elevated, whereas methionine was elevated in only 7 cases.ConclusionsThe study offers a reliable method for newborn screening for cystathionine β-synthase deficiency, reaching a sensitivity of up to 100%, even if samples are taken within the first 3 days of life.