Hyperchylomicronaemia due to lipoprotein lipase deficiency as a cause of false-positive newborn screening for biotinidase deficiency.

Two cases of molecular genetically proven lipoprotein lipase deficiency are reported. Both patients were detected owing to a false-positive neonatal screening test for biotinidase deficiency. We conclude that both the fluorimetric and the colorimetric screening tests for biotinidase deficiency used with dried blood samples are affected by severe hyperchylomicronaemia and that, most probably, severe plasma turbidity interferes with the assay.