Evidence lacking on effect of false-positive infant congenital hypothyroidism tests
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Few studies have evaluated infant and parental outcomes of false-positive results from newborn screening of congenital hypothyroidism, and most studies are low or moderate quality, according to a systematic review.
“This systematic review found insufficient evidence to determine whether false-positive newborn screening results for congenital hypothyroidism cause harm to infants or their parents,” Michelle M. Jack, PhD, MBBS (Hons), FRACP, clinical associate professor of pediatric endocrinology at the Northern Clinical School, Royal North Shore Hospital at University of Sydney, Australia, and colleagues wrote in a study published in Clinical Endocrinology. “These findings are relevant to the current debate regarding lowering thyroid-stimulating hormone thresholds in newborn screening, and whether the inevitable risk of increasing the number of false positives outweighs the benefits of identifying clinically relevant cases.”
Researchers conducted a systematic review of studies evaluating the effects of false-positive results on either infants or their parents following newborn screening of congenital hypothyroidism. Studies evaluating the risk of harm from a false-positive result were included in the analysis. Researchers searched Ovid MEDLINE, Ovid Embase, Ovid Emcare, EBSCO CINAHL Complete, Web of Science and Scopus on Feb. 20, 2020. Two researchers independently determined the quality of each study using the Critical Appraisal Skills Program.
Researchers found six relevant publications meeting the inclusion criteria. All were qualitative with semi-structured interviews, with four conducted in Sweden, one in Hong Kong and one in the Netherlands. Three studies were based on the same population of 102 infants. All studies examined parental stress, and two assessed infant stress. Two were moderate quality, and the remaining four were low quality.
“The use of unvalidated tools and interviews in these studies compromises the reliability and validity of findings,” the researchers wrote. “These qualitative methodologies lend themselves to problems of operationalizing variables, whereby information supplied by the parents cannot be quantified, so the individual processing the data depicts their personal understanding. There may also be inherent bias when the main researcher interviews both participants and interprets results.”
Due to heterogeneity of the study outcomes and survey instruments, researchers were unable to conduct a meta-analysis. Instead, a narrative synthesis of the study outcomes was in the review.
In the two studies examining infant stress, one found 75% of infants with a false-positive result were considered “disturbed” based on an observation from a child psychologist, and 44% were deemed disturbed based on Griffiths testing at 4 to 5 years. The second study stated 9% of infants showed “deviant” behavior toward the mother and uneven Griffiths test result around 4 years after the false-positive result. Children who were considered disturbed often had parents who poorly integrated their screening experience and an inadequate mother-child relationship.
Parental stress does not persist for most
Most of the six studies observed parental stress immediately after newborn screening, but not long term. Two studies found 72.7% of parents had good to very good coping ability 1 to 4 years after the false positive. In another study, all parents completing the Hamilton Rating Scale for anxiety scored a 0 at 2 years after screening.
In the Sweden studies, 54.5% mothers had difficulty with or discontinued breastfeeding after the false-positive result, 43% tended to seek hospital care in the first year of the infant’s life, and half of parents said they overprotect their infants. High life-stress scores were also associated with parental separation in the 5 years following a false-positive result.
Parental occupational stress, young maternal age, unsatisfactory housing, high general anxiety, previous miscarriage or abortion and perinatal complications were associated with a risk of harm to parents in most studies. Parental recollection and knowledge of the screening process, the timing and method of information delivery and a lack of support from staff providing information on the screening and results may have influenced parental stress, the studies reported.
More studies needed
The findings support the conclusion that false-positive results from newborn screening of congenital hypothyroidism may cause short-term parental stress, but the researchers wrote that the quality of the data is insufficient to assess risks.
“Prospective, controlled studies in the modern newborn screening environment are recommended to address the controversial issues associated with setting the TSH thresholds for newborn screening,” the researchers wrote.
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