Neonatal screen

Keywords: Dried blood spot, Guthrie test

Specimen:

Blood absorbed onto special paper. Sample taken 48 to 72 h after birth. (Samples taken 24-48 h are acceptable).

Method:

Diseases screened for include:

Aminoacidopathies, including Phenylketonuria, maple syrup urine disease, homocystinuria (tandem mass spectrometry).

Organic acidaemias, including methylmalonic aciduria, propionic acidaemia, isovaleric acidaemia, glutaric aciduria type I (tandem mass spectrometry).

Fatty acid oxidation defects, including carnitine transporter defect, carnitine translocase deficiency, carnitine palmitoyl transferase deficiencies, short-, medium-, and very long-chain and long-chain 3-hydroxy acyl-CoA dehydrogenase deficiencies, glutaric aciduria type I (tandem mass spectrometry).

Congenital Hypothyroidism: TSH (immunoassay).

Cystic fibrosis: trypsin(ogen) (immunoassay), mutation genotyping (molecular genetics: PCR based identification).

Galactosaemia: galactose-1-phosphate, galactose (tandem mass spectrometry). (Not performed in Victoria.)

Other rare inborn errors of metabolism - may vary from state to state.

Reference Interval:

Cut off value is set at an appropriate figure to avoid false negatives.

Application:

Population screening for severe, treatable disorders.

Interpretation:

A positive result indicates that the child is at risk of having that particular disorder. Confirmation of the diagnosis of the disorder requires further testing.

False negatives are very rare.

Hypothyroidism due to Hypopituitarism is not detected by a TSH screen, but the clinician is usually alerted to this possibility by clinical signs of intracranial disease.

Reference:

Brown ARD. Clin Biochem Rev 1985; 6: 3-13.

HGSA/RACP. Newborn bloodspot testing. Sydney, HGSA/RACP, 2011. www.hgsa.org.au/resources/hgsa-policies-and-position-statements

National Health and Medical Research Council (NHMRC). Genetics in Family Medicine: The Australian Handbook for General Practitioners. Canberra: NHMRC, 2011. https://www.nhmrc.gov.au/your-health/egenetics/health-practitioners/genetics-family-medicine-australian-handbook-general-prac