Newborn Screening
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Direct answer
A heel prick taken between 48 and 72 hours of life — after protein feeding has begun, before hospital discharge — can change the entire trajectory of a child with congenital hypothyroidism, congenital adrenal hyperplasia, galactosaemia, phenylketonuria, glucose-6-phosphate dehydrogenase deficiency or cystic fibrosis — conditions that damage irreversibly during the symptom-free window screening exploits. The logic test set: the disease must be serious, treatable, asymptomatic early, and common enough to justify testing, with a reliable test and an agreed follow-up pathway. Congenital hypothyroidism is the flagship — thyroid-stimulating hormone on the dried blood spot, treatment with levothyroxine within the first two weeks protecting near-normal intelligence — while India's structured programme is the Rashtriya Bal Swasthya Karyakram and targeted pilots rather than a universal expanded screen.
What you must remember
- Timing rule: the specimen is collected at 48-72 hours of age (or just before discharge), after three feeds of protein — earlier collection falsely raises thyroid-stimulating hormone (physiological neonatal surge) and misses phenylketonuria; later collection delays treatment.
- Core panel to know: thyroid-stimulating hormone for congenital hypothyroidism (Indian incidence estimates run above global averages), 17-hydroxyprogesterone for congenital adrenal hyperplasia, phenylalanine for phenylketonuria, galactosaemia (GALT enzyme or reducing substances), glucose-6-phosphate dehydrogenase assay, and immunoreactive trypsinogen for cystic fibrosis.
- Congenital hypothyroidism discipline: confirm with thyroid-stimulating hormone and free thyroxine on recall, start levothyroxine 10-15 microgram/kg/day within the first two weeks — every week of delay costs intelligence quotient points.
- Congenital adrenal hyperplasia screen: 17-hydroxyprogesterone, with attention to false positives in preterm and sick infants (higher normal values by weight and gestation) and the recall pathway for a salt-wasting crisis.
- Screening logic for vivas: Wilson-Jungner-style criteria — severe, treatable, latent phase, sensible incidence, reliable test, agreed pathway.
- Indian programme reality: no universal statutory newborn screening yet; Indian Council of Medical Research multi-state pilots covered congenital hypothyroidism and congenital adrenal hyperplasia, private hospital panels are widespread, and the Rashtriya Bal Swasthya Karyakram is the national clinical-screening scaffold.
- RBSK 4 Ds: defects at birth, deficiencies, diseases, developmental delays including disabilities — screened by mobile health teams from birth to 18 years for heart defects, cataract, deafness, cleft, neural tube defects and clubfoot.
- Beyond the blood spot: hearing screening by otoacoustic emissions before discharge (the one-three-six month rule), pulse oximetry for critical congenital heart disease at 24-48 hours, and the universal physical examination.
How to work through it
Walk a positive screen end to end, because the follow-up is the examinable half. A term infant's 72-hour dried blood spot shows thyroid-stimulating hormone of 85 micro-units per millilitre. The same week, not the same month: recall the infant, confirm with serum thyroid-stimulating hormone and free thyroxine, examine for goitre and midline defects, and start levothyroxine 10-15 microgram/kg/day while results are pending when the index is clearly high, titrating to a thyroid-stimulating hormone around 0.5-2 milli-units per litre. Two management facts earn marks: treatment must not wait for confirmatory tests when the screen is grossly abnormal, and persistent primary hypothyroidism at three years means lifelong therapy.
The mirror case is the recall you must handle carefully: a healthy preterm boy flagged for 17-hydroxyprogesterone. Prematurity raises the normal range: the recall looks for virilisation and salt-wasting, electrolytes are sent, and most such recalls normalise without steroids. Notify without alarming, recall promptly, confirm before labelling.
How the exam frames it
The two most repeated facts are the heel-prick timing (48-72 hours, after protein feeds — with the thyroid-stimulating hormone neonatal surge explaining the "not before 48 hours" rule) and congenital hypothyroidism as the commonest screened endocrinopathy with the highest benefit-cost justification. Indian framing asks what actually exists: the Indian Council of Medical Research pilot programmes demonstrated feasibility of congenital hypothyroidism screening in several states, but universal national screening is still aspirational, the pragmatic district answer is Rashtriya Bal Swasthya Karyakram clinical screening plus hearing screening and pulse oximetry where feasible. A favourite crossover question pairs the phenylketonuria screen with lifelong phenylalanine-restricted dietary therapy, and the galactosaemia screen with stopping galactose before confirmatory results in a sick infant.
Frequently asked questions
Why is the heel prick taken between 48 and 72 hours of life?
Before 48 hours the physiological neonatal thyroid-stimulating hormone surge causes false positives and phenylalanine has not risen without protein intake; after 72 hours, treatable days are lost.
Which screened condition has the clearest cognitive payoff from early treatment?
Congenital hypothyroidism — levothyroxine started within the first two weeks preserves near-normal intellectual outcome, whereas delayed treatment causes permanent cognitive impairment.
What does India's Rashtriya Bal Swasthya Karyakram screen for?
The 4 Ds — defects at birth, deficiencies, diseases, and developmental delays including disabilities — through clinical screening by dedicated teams from the newborn period to 18 years.
Why does prematurity cause false-positive congenital adrenal hyperplasia screens?
17-hydroxyprogesterone is physiologically higher in preterm infants, so laboratories apply gestation-specific cutoffs and recalls are evaluated with clinical and electrolyte assessment before labelling.
What non-blood-spot screening is recommended before discharge?
Hearing screening with otoacoustic emissions (or auditory brainstem response) and pulse oximetry of pre- and post-ductal saturations to detect critical congenital heart disease.