The impact of demographic factors on newborn TSH levels and congenital hypothyroidism screening. (11th June 2019) - Heather, Natasha L.
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.