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Congenital Hypothyroid Screening among Low Birth Weight Infants
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Congenital Hypothyroid Screening among Low Birth Weight Infants

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  • 1. Congenital Hypothyroid Screening among Low Birth Weight Infants, Michigan, 2005-2007 Steven J. Korzeniewski, MA, MSc, Maternal & Child Health Epidemiology Section Manager Violanda Grigorescu, MD, MSPH, William I. Young, Ph.D. Bureau of Epidemiology, Division of Genomics, Perinatal Health and Chronic Disease Epidemiology
  • 2. Outline
    • Brief overview of thyroid function and rationale for NICU protocol
    • NICU screening algorithm
    • Pre-Post NICU algorithm CH detection by birth weight
    • Concerns & discussion of newly detected cases (implications of three-year follow-up)
    • Conclusion/Public Health implications
  • 3. Hypothalamic-pituitary-thyroid axis
    • T 4 is stimulated by secretion of TSH by the pituitary.
    • Low T 4 (negative feedback) causes hypothalamus to secrete thyrotropin releasing hormone (TRH) which stimulates release of TSH thereby stimulating the thyroid gland to increase secretion of T 4 .
    • When the thyroid does not respond to TSH stimulation (primary CH), due to dysgenesis or dyshormonogenesis, the result is low T 4 and high TSH.
    Hypothalamus Pituitary Gland Thyroid (-) inhibition (+) stimulation TSH + T3, T4 - TRH + T3, T4 -
  • 4. CH Detection in Premature Infants
    • Maturity of the endocrine system influences initial dried blood spot TSH values.
      • Some premature infants with CH have late rising TSH and are therefore not detectable by an initial screen at 24-36hrs of life
    • NICU/LBW screening protocol implemented (2007) to account for unreliable screens in premature newborns
  • 5. NICU/LBW Screening Algorithm
  • 6. 1:1645 111893 68 1:1410 7050 5 1:211 2961 14 2007 1:1868 42961 23 1:1379 2757 2 1:199 996 5 1/1/08- 5/21/08 1:2283 114136 50 1:1460 7300 5 1:698 2793 4 2006 1:1863 108052 58 1:764 6873 9 1:517 2587 5 2005 Rate Screened Cases Rate Screened Cases Rate Screened Cases > 2500g 1800-2499g < 1800g Birth Weight Birth Year CH Cases by Birth Weight & Birth Year, Michigan, 1/1/2005-5/21/2008
  • 7. Number of Infants Screened by Birth Weight, Michigan, 2007   - 100 121,080 91.92 111,291 >=2500g 6,995 8.08 9,789 3.65 4,422 2200-2499g 2,573 4.43 5,367 1.28 1,554 2000-2199g 1,019 3.15 3,813 0.84 1,019 1800-1999g   - 2.31 2,794 2.31 2,794 < 1800g Estimated Number of Infants Added to the NICU Protocol (Cumulative) Cumulative % Cumulative Frequency % Frequency Birth Weight
  • 8. NICU Protocol Evaluation Conclusions
    • NICU protocol inclusion criteria currently does not consider gestational age.
      • GA is thought to be a better indicator of maturity than BW; however, concerns about data quality have led the latter to be used.
      • Adding very preterm and below (GA < 32 wks) infants would add 215 infants based on 2007 data.
    • We are evaluating the impact of:
      • increasing the birthweight inclusion criterion to ~2300g,
      • adding very preterm and below (GA < 32 wks) infants, and
      • eliminating 2 nd screens for infants born weighing less than ~1,000g-1,500g.
    • Clinical Laboratory Standards Institute (CLSI) has a subcommittee working on a proposed standard for NBS of SCBU/NICU infants
  • 9. Who are we detecting?
    • Is the 10 fold increase in risk of CH among infants < 1800g compared to those >= 1800g real ?
    • Standard of care is to follow-up CH cases until at least age three years (AAP Guidelines)
    • Diagnostic verification recommended (permanent vs. transient CH)
      • Thyroid function trial
    • Rate and outcome of diagnostic verification unknown
  • 10. CH Three Year Follow-up of ‘ Borderline ’ Cases
    • ‘ Borderline’ was initially considered as having pre-treatment serum TSH values below the 15 Th percentile.
      • We recently expanded our criteria to include cases below the 25th percentile and now plan to follow all cases to age 3 years.
    • Survey developed and pilot tested in collaboration with PEAC endocrinologists
    • Medical management data maintained by NBS Follow-up program used to locate cases’ physicians.
      • LTFU mitigated by use of MCIR and phone based survey
  • 11. Demographics of Michigan CH Cases Detected by NBS Classified by Pre-Treatment Serum TSH/FT4 Values, 9/2003-9/2007 25.8 58 53.1 3001 38.5 30.43% 70 FT4 >=.9, TSH <40 55.6 66.7 50 2461 34.1 3.91% 9 FT4 < .9, TSH < 40 18.2 33.3 61.5 3254 38 20.87% 48 FT4 >=.9, TSH >=40 19.6 39.2 79.1 3156 37.9 44.78% 103 FT4 < .9, TSH >=40 NICU (%) Male (%) White (%) Mean BW Mean GA % N Classification
  • 12.  
  • 13. Preliminary Findings of the CH Three year follow-up study
    • Preliminary findings indicate:
      • 47% (9/19) of cases with completed diagnostic re-evaluation to date appear not to have permanent CH.
      • A surprising number of patients (families) have stopped treatment of their own accord (7/23 with completed follow-up); this phenomenon requires further study.
        • One case (family) described miscommunication with health care provider and lack of follow-up as impetus to treatment cessation.
      • While all patients who stopped treatment on their own are thought to be transient CH (confirmation of transient CH is pending TSH value receipt- two patients have provided such confirmation to date), only 2/12 cases evaluated by an endocrinologist/hcp are considered transient.
        • This finding may have implications for the method of diagnostic re-evaluation.
        • Some cases were confirmed based on increasing treatment dosage at approximately 6 months of age; should this preclude three year thyroid challenge?
        • Questions remain about process and outcome of three year CH re-evaluation.
  • 14. Overall Conclusions
    • Newborn screening at 24-36hrs of life does not detect children with CH having late rising TSH
    • NICU screening protocols increase CH detection significantly
    • It is possible that some moderately LBW children having CH and late rising TSH remain undetected.
    • NICU algorithm inclusion criteria require further evaluation
      • Gestational age should likely be considered
    • It is possible that many borderline cases, which likely includes children with CH detected by the 2 nd or 3 rd screen, are transient
      • Such cases are more likely to be male, LBW, NICU births, and/or racial minorities
    • Three year follow-up is of critical importance to differentiate transient from permanent CH, particularly in states conducting routine second screens or having NICU/LBW protocols.
  • 15. Acknowledgements
    • Bill Young, Manger, Newborn Screening Follow-up Program
    • Violanda Grigorescu, Director, Division of Genomics, Perinatal Health & Chronic Disease Epidemiology
    • Newborn Screening Follow-up Staff
    • Pediatric Endocrine Advisory Committee
  • 16. Thank You [email_address] http://www.michigan.gov/mchepi