NBS Basics & Indian Scene - First Steps, First Screens
- Definition: Population-wide testing of newborns for specific treatable disorders before symptoms manifest.
- Goals: Early diagnosis & intervention to ↓ morbidity/mortality, improve Quality of Life (QoL).
- Wilson-Jungner Criteria (adapted for NBS): Key principles for justifying a screening program.
- 📌 Mnemonic: SCATTER
- Serious Condition: Disease poses a significant health burden.
- Acceptable Test: Reliable, valid, and acceptable to population.
- Treatment Effective: Available treatment that improves prognosis.
- Resources: Adequate facilities for diagnosis, treatment, and follow-up.
- 📌 Mnemonic: SCATTER
- NBS in India:
- No unified national program; state-level variations.
- IAP Recommendations: Strong advocacy for universal NBS.
- RBSK: Includes some NBS components (e.g., Congenital Hypothyroidism (CH), hearing loss).
- Active programs in states like Kerala, Goa; pilot projects elsewhere.
- Commonly Screened Conditions (India): Congenital Hypothyroidism (CH), Congenital Adrenal Hyperplasia (CAH), G6PD deficiency. Others include PKU, Galactosemia depending on regional prevalence & resources.
⭐ Newborn screening aims for early identification of infants with treatable conditions before they become symptomatic.
The "Must-Know" Disorders - Tiny Clues, Major Conditions
⭐ Congenital Hypothyroidism is the most common preventable cause of intellectual disability worldwide.
| Disorder | Defect (Enzyme/Protein) | Inheritance | Screening Test | Confirmatory Test | Key Features (Untreated) / Benefit of Early Detection |
|---|---|---|---|---|---|
| Congenital Hypothyroidism (CH) | Thyroid dysgenesis/dyshormonogenesis | Sporadic | ↑TSH (> 20 µIU/mL), ↓T4 | Repeat TSH, Free T4; Thyroid scan/USG | Prevents severe intellectual disability, growth failure. Untreated: coarse facies, umbilical hernia, prolonged jaundice. |
| Phenylketonuria (PKU) | Phenylalanine hydroxylase (PAH) deficiency | AR | ↑Phenylalanine (Phe) levels (MS/MS) | Quantitative plasma Phe; Genetic testing | Prevents severe intellectual disability, seizures, eczema. Untreated: mousy odor. 📌 PKU: Phenylalanine Kills Understanding. |
| Galactosemia (Classical) | Galactose-1-Phosphate Uridyltransferase (GALT) | AR | ↓GALT activity, ↑Total Galactose/Gal-1-P | GALT enzyme assay (RBCs); Genetic testing | Prevents FTT, jaundice, hepatomegaly, cataracts, E. coli sepsis, intellectual disability. |
| Congenital Adrenal Hyperplasia (CAH) | 21-hydroxylase deficiency (>90%) | AR | ↑17-hydroxyprogesterone (17-OHP) | ACTH stim test; ↓Na, ↑K; Genetic testing | Prevents salt-wasting crisis, ambiguous genitalia (females), virilization. Ensures correct sex assignment, normal growth. |
| G6PD Deficiency | Glucose-6-Phosphate Dehydrogenase | X-linked | ↓G6PD enzyme activity (fluorescent spot test) | Quantitative G6PD enzyme assay | Avoids triggers for neonatal jaundice & acute hemolytic anemia (drugs, infections, fava beans). |
| Biotinidase Deficiency | Biotinidase enzyme deficiency | AR | ↓Biotinidase activity (MS/MS) | Serum biotinidase assay; Genetic testing | Prevents seizures, hypotonia, rash, alopecia, developmental delay with biotin supplementation. |
Screening Logistics & Follow-Up - Dots, Drops, Decisions
- Sample Collection (Dried Blood Spot - DBS):
- Timing: Ideal 24-72 hours of age; after adequate protein feeding (e.g., PKU).
- Site: Heel prick (medial/lateral plantar surface).
- Method: Blood drops on filter paper (Guthrie card).
- Factors Affecting Results: Prematurity (transient ↑17-OHP, ↓T4), TPN, blood transfusion (masking), antibiotics, maternal diet/meds.
- Interpretation & Recall: Use analyte-specific cut-offs; manage false positives/negatives; clear recall criteria for positive screens.
- Follow-up Protocol:
- Prompt confirmatory tests (e.g., MS/MS, enzyme assays, DNA).
- Specialist referral, timely treatment initiation.
- Genetic counseling for family.
- Other Universal Screenings:
- UNHS: OAE (screening), BERA (diagnostic if OAE fails).
- CCHD: Pulse oximetry (24-48 hrs, pre- & post-ductal $SpO_2$ difference/low saturation).
⭐ A positive newborn screen is not a diagnosis but indicates high risk and requires prompt confirmatory testing.
High‑Yield Points - ⚡ Biggest Takeaways
- NBS facilitates early diagnosis and management of critical congenital conditions.
- Optimal sampling: 24-72 hours post-birth, after feeding, via heel prick.
- Core Indian panel: Congenital Hypothyroidism (CH), CAH, G6PD deficiency.
- Tandem Mass Spectrometry (TMS) allows simultaneous screening for numerous disorders.
- Phenylketonuria (PKU) detected by Guthrie test or TMS.
- Screen for Galactosemia (GALT deficiency) and Biotinidase deficiency.
- Pulse oximetry for Critical Congenital Heart Disease (CCHD) screening is vital.
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