12.2 Universal Newborn Screening: Hearing, CCHD & Dried Blood Spot

Universal Newborn Screenings

1. Universal Newborn Hearing Screening

Hearing impairment is the most common congenital condition, affecting 1 to 3 per 1,000 term infants. Undetected hearing loss leads to severe, irreversible speech, language, and cognitive delays. Screening must be performed prior to hospital discharge under the national "1-3-6" Benchmark:

• Screen by 1 month of age.
• Comprehensive diagnostic audiological evaluation by 3 months of age for infants who do not pass the initial screen.
• Enrollment in multidisciplinary early intervention services by 6 months of age.

Screening Modalities

• Otoacoustic Emissions (OAE): A miniature probe in the ear canal emits soft acoustic clicks and measures sound waves generated by the outer hair cells of the cochlea. Quick, non-invasive; however, vernix or fluid in the external ear canal can yield false-positive fails.
• Automated Auditory Brainstem Response (AABR): Scalp electrodes measure electrophysiologic neural transmission from the cochlea through the eighth cranial nerve into the brainstem. AABR is mandatory for infants in the NICU >5 days because, unlike OAE, it detects Auditory Neuropathy Spectrum Disorder (ANSD).

2. Critical Congenital Heart Disease (CCHD) Pulse Oximetry Screening

Critical congenital heart defects (CCHD)—such as hypoplastic left heart syndrome, transposition of the great arteries, tetralogy of Fallot, total anomalous pulmonary venous return, truncus arteriosus, tricuspid atresia, and coarctation of the aorta—depend on ductal patency. When the ductus arteriosus closes post-discharge, these infants suffer catastrophic cardiovascular collapse.

CCHD Screening Protocol (Performed at ≥24 hours of life)
├── Measure SpO2: RIGHT HAND (Pre-ductal) & EITHER FOOT (Post-ductal)
├── PASS: SpO2 ≥95% in BOTH hand & foot AND ≤3% difference between hand and foot
├── IMMEDIATE FAIL: SpO2 <90% in EITHER hand or foot ──> Stat Echo & Pediatric Evaluation
└── RE-TEST (90-94% in either, or >3% difference): Repeat in 1 hr (up to 3 tests total)

• Screening Timing: Performed at ≥24 hours of life (to minimize false-positives caused by transitional pulmonary hemodynamics) or immediately prior to discharge if discharged <24 hours.
• Sensor Placement: Pulse oximeter sensor placed on the RIGHT HAND (pre-ductal) and EITHER FOOT (post-ductal).
• Algorithmic Interpretation:
  • PASS: Oxygen saturation is ≥95% in BOTH the right hand and either foot, AND the difference between the right hand and foot is ≤3%. The screen is complete.
  • IMMEDIATE FAIL: Oxygen saturation is <90% in EITHER the right hand or foot. Requires immediate medical evaluation, supplemental oxygen assessment, and an urgent pediatric echocardiogram.
  • INDETERMINATE (RE-TEST ZONE): Oxygen saturation is 90% to 94% in either the hand or foot, OR there is a >3% difference between the hand and foot. The infant must be re-tested in 1 hour.
  • Repeat Testing Protocol: If the second test remains in the indeterminate range, repeat a third time in 1 hour. If the third test still demonstrates 90% to 94% or >3% difference, the screen is classified as a FAIL, requiring an immediate clinical evaluation and pediatric echocardiogram.

3. Dried Blood Spot Metabolic Screening

Collected via capillary heel stick onto specialized filter paper (Guthrie card) between 24 and 48 hours of life, ensuring the infant has ingested protein feedings for at least 24 hours (essential for detecting amino acid disorders). Screened conditions on the Recommended Uniform Screening Panel (RUSP) include:

• Phenylketonuria (PKU): Deficiency of phenylalanine hydroxylase. Accumulation of phenylalanine causes profound, irreversible intellectual disability, microcephaly, and seizures. Immediate initiation of a low-phenylalanine medical formula prevents cognitive damage.
• Congenital Hypothyroidism: Elevated TSH with decreased free T4. Represents the most common preventable cause of intellectual disability (cretinism). Treatment with oral levothyroxine initiated before 2 weeks of age preserves normal cognitive potential.
• Galactosemia: Deficiency of galactose-1-phosphate uridyltransferase (GALT). Ingestion of lactose (glucose + galactose) in breast milk or standard formula causes rapid accumulation of galactose-1-phosphate, resulting in E. coli sepsis, jaundice, cataracts, hepatic cirrhosis, and death. Immediate, permanent transition to soy-based, galactose-free formula is life-saving; breastfeeding is strictly contraindicated.
• Sickle Cell Disease & Hemoglobinopathies: Identifies HbSS, HbSC, and beta-thalassemia via isoelectric focusing or HPLC. Initiating daily prophylactic oral penicillin by 2 months of age and pneumococcal vaccination prevents fatal Streptococcus pneumoniae sepsis.
• Cystic Fibrosis (CF): Evaluates immunoreactive trypsinogen (IRT), followed by DNA mutation testing for CFTR gene variants.
• Congenital Adrenal Hyperplasia (CAH): Most commonly 21-hydroxylase deficiency, leading to elevated 17-hydroxyprogesterone (17-OHP). Causes life-threatening salt-wasting crisis (hyponatremia, hyperkalemia, vascular collapse) in the second week of life, and ambiguous genitalia in genetic females.
• Severe Combined Immunodeficiency (SCID): Detected via quantitation of T-cell receptor excision circles (TRECs), identifying severe T-cell lymphopenia before fatal opportunistic infections occur.

Timing, Specimen Quality & Special Populations

The dried blood spot is the screen most often invalidated by process error rather than by biology, and the timing rules are heavily tested:

• Collect between 24 and 48 hours of age. Before 24 hours, the metabolites that the panel detects have not had time to accumulate after feeding began, and phenylalanine in particular can still be normal in an affected infant.
• If the specimen was unavoidably collected before 24 hours — typically because of an early discharge or transfer — a repeat specimen is required, usually by about 1 to 2 weeks of age.
• Transfusion invalidates the screen for hemoglobinopathies and several other analytes, because the transfused donor cells are what get tested. Whenever possible, draw the specimen before transfusing; if not, a repeat is scheduled after the donor cells have cleared.
• Preterm, low-birth-weight, and critically ill infants are commonly screened on a repeat schedule, because immature hepatic and endocrine function and parenteral nutrition both distort results.
• Specimen quality is the midwife's responsibility. Fill each printed circle completely with a single application of free-flowing blood from one side of the card, do not layer or milk the heel, air-dry horizontally away from heat and direct sunlight, and never place the card in a plastic bag while wet. A layered, clotted, or insufficient spot yields an "unsatisfactory specimen" result and costs days.

Predischarge Bilirubin Assessment

Alongside the three state-mandated screens, current newborn practice includes a universal predischarge bilirubin measurement — transcutaneous or serum — in every infant, plotted on an hour-specific nomogram together with the infant's gestational age and risk factors to determine both the need for treatment and the timing of follow-up. It is not part of the state newborn screening program, but it is universal in practice and is the fourth thing that must be documented before any newborn goes home.

Communicating a Positive Screen

The single most important counseling principle: a screen is not a diagnosis. These panels are deliberately built for high sensitivity, so false positives substantially outnumber true positives, and an out-of-range result means only that confirmatory testing is needed now.

• Contact the family promptly and by telephone or in person, never by a message that leaves them to interpret it alone.
• State plainly that the screen was out of range, that most out-of-range screens turn out to be normal on confirmatory testing, and that the next step is a specific test on a specific date.
• Arrange the confirmatory test and the specialist referral before ending the conversation, and document who is responsible for the result.
• Out-of-hospital births carry the same obligations. The midwife who attends a home or birth-center birth owns the hearing screen, the pulse oximetry screen, the blood spot, and the bilirubin check — including tracking the results to closure.