Since the early days of NBS, there has been concern that parents of infants with false-positive NBS results overuse health care services because they believe their child to be persistently vulnerable to illness.10
Previous studies that have used voluntary enrollment of study participants instead of a population-based methodology have yielded conflicting results.3,4
In this study, which represents the largest and only population-based analysis to date, we found that only preterm infants with false-positive NBS results had more acute outpatient visits than their preterm counterparts with normal NBS results. We did not find such a difference among term infants. Furthermore, regardless of prematurity status, we found no difference in outpatient well visits, ED visits, or hospitalizations between infants with false-positive and those with normal NBS results.
There are a number of possible explanations for our findings. First, it is possible that parents of premature infants with false-positive NBS results make more acute outpatient visits because they are overanxious about both the child's history of prematurity and the false-positive NBS result. However, others might counter that parents of preterm infants deal with so many concerns about their child's tenuous health that parents are unlikely to pay much attention to a false-positive NBS result. Second, it is conceivable that preterm infants with false-positive NBS results have more acute outpatient visits because of their underlying chronic illness. Premature infants are known to have a higher rate of false-positive results because of illness-related stress11
and the use of screening cutoffs based on studies of term infants.12,13
So it is possible that, despite our best efforts, we were unable to fully control for the confounding influence of chronic illness on health care use in preterm infants with false-positive results. Nonetheless, additional studies should be performed to examine the psychosocial effects of a false-positive NBS result on parents of preterm infants. Finally, although case reports have identified cases in which infants with false-positive results have been inappropriately diagnosed as disease free,14
this phenomenon is likely to be uncommon and thus is not likely to account for our study findings.
We did not find any differences between infants with false-positive and those with normal NBS results for other health care visit types (eg, well visits, ED visits, hospitalizations), regardless of prematurity status. There are a number of plausible explanations for this null finding. First, it is possible that the phenomenon of parental anxiety that leads to increased health care use15
is present only in certain subgroups, such as parents who had difficulty conceiving, those with pregnancy complications, or even first-time parents. These subgroups may be “primed” to become concerned about the lasting significance of their child's false-positive NBS result. If so, it is unlikely that these subgroups will be identified in an aggregate analysis of a study population.
Alternatively, it may be that there are certain types of false-positive results, such as those for disorders that can be more immediately life-threatening, such as MCADD (medium chain acyl CoA dehydrogenase deficiency). Hearing that their newborn may have a potentially life-threatening illness leave a more powerful and lasting effect on parents' perceptions of their child's health than if they had been told that that the disorder was not immediately life threatening.16
We had neither sufficient numbers of these disorders nor the necessary parental medical and social information to explore either of these hypotheses in the current analysis.
It is conceivable that our findings are unique to a continuously enrolled Medicaid population. Children with private insurance have greater outpatient health care use than children with public insurance.17
Although some of this discrepancy in use may be because of lack of access to care among the publicly insured, it could also be fueled by the phenomenon of the “worried well.” Future studies will need to examine the relationship between false-positive NBS results and health care use in a privately insured population.
There are limitations of this study that should be noted. As evidenced by the fact that every child in our analysis did not have a claim record for their birth admission (n = 8729 [17%]), it is likely that our collection of claims did not represent all of the health care visits for the study population. Nonetheless, we have no reason to suspect there would be a differential bias for missing claims according to NBS result. As noted above, we may not have completely controlled for chronic illness, and so our results may be explained, in part, by residual confounding. Finally, because we examined only health care use in the first 12 months of life, children may not have had enough opportunities to seek acute care for illness. As a result, we might have failed to detect a difference between infants with false-positive and normal NBS results that would become evident in the next few years of life when the ratio of acute to well health care visits rises.
In addition, it is important to recognize that increased health care utilization is only one potential manifestation of parental anxiety about false-positive NBS results. Although we did not find a link between false-positive NBS results and increased health care visits, we cannot rule out that parental anxiety about false-positive results may have been present and could conceivably have been manifested through other actions, such as decisions to forego future childbearing or restriction of the child's activity.18
Additional studies are needed to explore the presence and scope of maladaptive parental behaviors that might result from persistent parental anxiety regarding false-positive NBS results.