The impact of demographic factors on newborn TSH levels and congenital hypothyroidism screening

Abstract

Context Optimal newborn screening thyroid‐stimulating hormone (TSH) cut‐offs are contentious. Analysis of demographic factors that impact screen TSH levels may help explain international variance and provide guidance to screening programmes. Objective To determine the influence of demographic factors on newborn screening TSH levels and screening performance parameters. Design and Setting National, retrospective population study using blood spot TSH cards from the New Zealand newborn screening programme in 2010‐2015. Patients 325 685 blood spot cards. Main Outcome Measures Likelihood of exceeding specific TSH thresholds (TSH ≥5, ≥10 and ≥15 mIU/L) and group‐specific screening performance parameters. Results The likelihood of high TSH levels differed between ethnic groups. Pacific Island infants were more than twice as likely to have high‐normal TSH levels (≥5 and ≥10 mIU/L) and nearly twice as likely to have a positive screen (≥15 mIU/L) as New Zealand Europeans. Māori or Chinese ethnicity, male sex, younger gestational age and greater socio‐economic deprivation scores were also associated with high‐normal TSH levels. At a TSH threshold ≥15 mIU/L, screening sensitivity was lowest (88.89% vs 95.83% overall) and PPV greatest (88.89% vs 62.84%) amongst Asian infants. Early samples were more than three times as likely to reach the screen‐positive threshold and more likely to yield a false‐positive result (PPV 20.00% vs 68.87%, P = 0.004). Conclusions Newborn TSH levels are impacted by a number of demographic variables, particularly ethnicity and age at sample collection. Screening performance may be improved through the use of targeted thresholds.

Validity of Six Month L-Thyroxine Dose for Differentiation of Transient or Permanent Congenital Hypothyroidism

“…However, a considerable shift has been observed in the incidence rate as well as the ratio of transient and permanent cases with a change in the cut-off values which had been used for neonatal screening programs ( 5 , 8 , 15 ). In our series an increase in the number of cases with transient hypothyroidism can be attributed to moderate iodine deficiency, while the high rate of permanent cases may be attributed to the high rate of consanguinity (55%) which may be associated with increased risk of autosomal recessive dyshormonogenesis ( 5 , 16 , 17 , 18 ).…”

Outcomes of lowered newborn screening thresholds for congenital hypothyroidism

“…Another potential confounder is ethnicity, with some evidence that incidence and subtypes of CH vary by race and ethnicity 1 . Within Australasia, several demographic factors are linked to elevated NBS b‐TSH levels, including being from a non‐English speaking background, or belonging to minority ethnic groups such as New Zealand Maori 22 . Governmental regulations prevented the collection of ethnicity data during NBS in NSW.…”

“…1 Within Australasia, several demographic factors are linked to elevated NBS b-TSH levels, including being from a non-English speaking background, or belonging to minority ethnic groups such as New Zealand Maori. 22 Governmental regulations prevented the collection of ethnicity data during NBS in NSW. Maternal ethnicity is also not collected at a population level, however, maternal country of birth is collected in the Perinatal Data Collection.…”

A Positive Newborn Screen for Congenital Hypothyroidism in a Clinically Euthyroid Neonate—Avoiding Unnecessary Treatment

“…This met New Zealand criteria for a positive screen and direct referral for diagnostic assessment (TSH ≥ 20 mU/L whole blood, GSP, Perkin Elmer) [ 5 ]. A blood sample was collected for diagnostic serum TFTs, and she was prescribed a loading dose of L-thyroxine at 10 mcg/kg/day, to be taken after review of TFTs [ 6 ]. Serum TFTs demonstrated high free T4 of 54 pmol/L (10–40) and a mildly elevated TSH of 14.8 mU/L.…”