NEONATAL SCREENING M.Prasad Naidu MSc Medical Biochemistry, Ph.D.Research Scholar

Most Inborn errors of metabolism presenting in the neonatal period are leathal if specific treatment is not initiated immediately. Specific diagnosis , even in an infant in whom death seems inevitable, is of great importance for genetic counseling of the family. Every effort should be made to determine the diagnosis while the infant is alive; A specific diagnosis may be established by measurement of abnormal metabolites in body fluids, by assAy of the specific enzyme activity, or by identification of the mutant gene.

In an attempt to standerdize newborn screening programs, the american college of medical genetics (acmg) recommends that every baby born in the united states be screened for a uniform panel of 29 disorders. The american academy of pediatrics also endorse the recommendation by the acmg

Disorders of organic acid metabolism Disorders recmmended by the acmg task force for inclusion in newborn screening Disorders of organic acid metabolism 1. Isovaleric acidemia 2. Glutaric aciduria type 1 3-hydroxy-3-methylglutaric aciduria Multiple carboxylase defyciency Methylmalonic acidemia, mutase deficiency form. 3-methylcrotonyl-c0-a carboxylase deficiency Methylmalonic acidemia, cbl a, & cbl b forms Propionic acidemia Beta ketothiolase deficiency

Disorders of fatty acid metabolism Medium chain acyl c0-a dehydrogenase deficiency. Very long chain acyl c0-a dehydrogenase deficiency. Long chain l-3-hydroxy acyl c0-a dehydrogenase deficiency Trifunctional protein deficiency Carnitine uptake defect. Hemoglobinopathies Sickle cell anemia Hemoglobin s-β-THALASSEMIA HEMOGLOBIN SC DISEASE.

DISORDERS OF AMINO-ACID METABOLISM PHENYLKETONURIA MAPLE SYRUP URINE DISEASE HOMOCYSTINURIA CITRULLINEMIA ARGININOSUCCINIC ACIDEMIA TYROSINEMIA TYPE 1 OTHER DISORDERS CONGENITAL HYPOTHYROIDISM BIOTINIDASE DEFICIENCY CONGENITAL ADRENAL HYPERPLASIA GALACTOSEMIA CYSTIC FIBROSIS HEARING DEFICIENCY.

INBORN ERRORS OF AMINO ACID METABOLISM ASSOCIATED WITH PECULIAR ODOUR INBORN ERROR OF METABOLISM 1. PHENYLKETONURIA TYROSINEMIA MAPLE SYRUP URINE DISEASE GLUTARIC ACIDEMIA ISOVALERIC ACIDEMIA URINE ODOUR MOUSY OR MUSTY BOILED CABBAGE, RANCID BUTTER MAPLE SYRUP, BURNT SUGAR SWEETY FEET, ACRID SWEETY FEET, ACRID.

Phenylketonuria . 1 : 10,000 Lab diagnosis. Blood phenylalanine Normal level is 1 mg/dl. IN PKU, THE LEVEL IS > 20 mg/dl. URINE PHENYLEKETONES 500-3000 mg / day. Tandem mass spectroscopy : most reliable, costly. Guthrie test : rapid screening test Ferric chloride test Dna probes

Guthrie test : Was developed in 1961 by robert guthrie It is a rapid screening test Certain strains of bacillus subtilis need phenylalanine as an essential growth factor Bacterial growth is proportional to the phenylalanine content in the patients blood. Guthrie was the father of a mentally challenged child. He developed a rapid screening test for pku

Ferric chloride test. Earlier in 1934, asbjorn folling, a norwegian biochemist introduced the use of ferric chloride test in urine of a mentally retarded child with decreased skin pigmentation & mousy odor of urine. A transient blue green colour is a positive test. But this is a less reliable test.

Tandem mass spectrometry [ ms-ms ] Is a technically advanced method in which many compounds are seperated by molecular weight. The process requires roughly 2 min / sample & can detect 20 or more inborn errors of metabolism. Blood obtained by heal-prick is applied to a filter paper, four to six circles approximately 1 cm in diameter, allowed to dry in air, & sent to a screening laboratory for analysis.

Tsh (thyroid stimulating hormone) SERUM Birth-4 d---1.0-28.9mIU/L 2-20 wk ---1.7-9.1 5 mo – 20 yr---0.7-6.4 THYROXIN, TOTAL 1-3 D---106-256 nmol/L 1 WK---77-205 1-12 mo---79-192 1-3 yr---88-174 3-10 yr---71-165 10-20 yr---54-167 Thyroxin, free 3 d---26-631 pmol/L 1 yr---12-33 10 yr---10-28 Adults---10-30

LABORATERY FINDINGS IN HYPOTHYROIDISM Triiodothyronine, total . serum Newborn---1.16-4.0 nmol / L 1-5 yr---1.54-4.0 5-10 yr---1.39-3.70 10-15 yr---1.23-2.23 Adults---1.77-2.93 Triiodothyronine, free . 1-3 d--- 3.1 - 9.4 nmol / L 6 wk--- 3.7- 8.6 Adult ( 20- 50 yr )---3.5-10.0 LABORATERY FINDINGS IN HYPOTHYROIDISM T3&T4 IN BLOOD TSH RESPONSE TO TRH PRIMARY DECREASED EXAGGERATED RESPONCE SECONDARY NO RESPONCE

Measurement of t3 , t4 & tsh levels in blood by hypothyroidism. Assay of hormones. Measurement of t3 , t4 & tsh levels in blood by Radio immuno assay ( ria) or elisa Chemiluminiscent immuno assay ( c.l.i.a ) immunofluorescence

Adrenogenital syndrome ( ag syndrome ) There is congenital deficiency of steroid hydroxylases leading to deficient secretion of cortisol. Since cortisol, the major feedback effector is not present, acth secretion continues leading to congenital adrenal hyperplasia ( cah ). 21 - hydroxylase defyciency : most common type Cortisol totally absent Lack of feedback leads to increased androgen synthesis. Virilization of female children who develop ambiguous genitelia.

Immunoassay for 17- alpha-hydroxy progesterone Normal value : urine 11-hydroxylase deficiency In this condition symptoms are more serious. The hypertensive veriety of ag syndrome manifests & the child may not survive. NORMAL VALUE OF CORTISOL : plasma 9 AM -------------------------130 – 600 nmol / L MIDNIGHT---------------30 –- 130 nmol / L Immunoassay for 17- alpha-hydroxy progesterone Normal value : urine female : 5.5 – 22 μmol / d MALE : 8 – 22 μmol / d

Maple syrup urine disease Incidence 1 : I lakh. Deficient decarboxylation of branched chain keto acids Laboratory findings Dinitro phenyl hydrazine test (dnph) : yellow colour indicates positive test Ninhydrin test Thin layer chromatography Hplc Tandem mass spectrometry

GALACTOSEMIA. GALACTOSE-1-PHOSPHATE URIDYL TRANSFERASE DEFICIENCY HYPOGLYCEMIA JAUNDICE MENTAL RETARDATION GALACTOSURIA CONGENITAL CATARACT LACTOSE FREE DIET

SICKLE CELL HEMOGLOBIN ( HbS ) GLUTAMIC ACID IN 6TH POSITION----BETA CHAIN HbA ----------------------CHANGED TO VALINE. POLIMERIZATION OF HEMOGLOBIN---SICKLE SHAPED RBC’s. HYPOXIA ELECTROPHORESIS : HbS less negatively charged.DECREASED MOBILITY TOWARDS POSITIVE POLE. SICKLING TEST : SODIUM DITHIONITE

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