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Letter to the editor:

Journal of Perinatology volume 38, page 767 (2018)Cite this article

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We read with interest the article by Nelin et al. [1] on the mortality differences by prophylactic indomethacin (PI) treatment status in extremely pre-term newborns transferred to the study hospital. The authors found that the risk of death among infants treated with PI was about half that of unexposed infants (“controls” in the paper, RR = 0.52), while previous randomized controlled trials reported no survival benefit of PI [2, 3]. This difference could be due to selection bias and confounding in the study by Nelin et al. [1]

The study population was restricted to outborn infants; the authors saw no differences in intra-ventricular hemorrhage between PI-treated and untreated infants, contrary to the results of previous large RCTs enrolling both inborns and outborns. This suggests that the studied population was not representative of the underlying population of extremely pre-term infants. Furthermore, the observed results may not even apply to outborn infants. Extremely pre-term newborns are at high risk of death, especially in the first few days of life [4]; thus, only those who survived until transfer were included in the study. If the conditions for which PI is indicated are more likely to result in early death, then those who survive till transfer would have better prognosis (the slightly older age at admission of PI-treated infants corroborates this hypothesis). Another potential source of selection bias is the exclusion of those infants with no information on exposure (166 (20%) of the 837 transferred infants). If the association between PI and mortality in this group differed from that among those in the analysis, the estimated association would be biased.

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References

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Authors and Affiliations

  1. Neonatology, Montreal Children’s Hospital, McGill University, Montreal, Canada

    Gabriel Altit

  2. Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, Canada

    Gabriel Altit, Olga Basso, Sonia M. Grandi & Seungmi Yang

  3. Obstetrics & Gynecology, Royal Victoria Hospital, McGill University, Montreal, Canada

    Olga Basso

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  1. Gabriel Altit
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  2. Olga Basso
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  4. Seungmi Yang
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Correspondence to Gabriel Altit.

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Altit, G., Basso, O., Grandi, S.M. et al. Letter to the editor:. J Perinatol 38, 767 (2018). https://doi.org/10.1038/s41372-018-0083-1

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