Effect of Sample Timing, Preterm Birth, Diet, Transfusion, and Total Parenteral Nutrition on Newborn Screening Results

DisorderSample TimingDietPreterm BirthTransfusionTotal Parenteral Nutrition
Biotinidase deficiency>90 d after transfusion
Congenital adrenal hyperplasia↑ in false-positives first 24 h↑ in false-positives secondary to normal ↑ in 17-hydroxyprogesteroneA few hours (estimated) after transfusion
Congenital hearing loss
Congenital hypothyroidism
    Thyrotropin method↑ in false-positives before 48 h
    Thyroxine method↑ in false-positives and false-negatives
Cystic fibrosis↑ in false-positives in first 24 hNot knownNot knownInterferes with mutation analysis for 3–6 wk
    Galactose methodGalactose-containing formulaFalse-negative
    GALT method>90 d after transfusion
Homocystinuria>24 h; second test at 2–4 wk advisableAdequate protein intakeFalse-positive
Maple syrup urine diseaseFalse-positive
MCAD deficiencyBefore 8 d
PKUAdequate protein intakeFalse-positive
Sickle cell diseases and other hemoglobinopathies↑ in false-negatives with extreme preterm birth>90 d after transfusion
TyrosinemiaAdequate protein intakeIncreased likelihood of neonatal tyrosinemiaFalse-positive
  • — indicates no impact; ↑, increase.