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Is there a role for cohort studies after the publications of high-quality large RCTs on the association between erythropoietin and retinopathy of prematurity?

Journal of Perinatology volume 45, pages 1029–1030 (2025)Cite this article

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We thank Dr. Bahr and colleagues for their interest in our study [1]. We agree that there is a hierarchical structure regarding the level of evidence, in which systematic reviews of randomized controlled trials (RCTs) provide the highest level of evidence. Therefore, we should carefully interpret the results of our cohort study considering the results of previous high-quality RCTs.

We consider the level of evidence for our cohort study to be 2B, based on the system used by Dr. Bahr [1]. Previous studies have reported no association between erythropoietin use and retinopathy of prematurity (ROP) [2], although the RCT by Ohls et al. [2] included in Dr. Bahr’s letter [1] had not been formally published as a full-text article at the publication of our study [3]. In contrast, our cohort study found an association between erythropoietin and ROP [3]. The possibility of confounding bias cannot be ruled out. However, the following two points in our study, which differ from the existing RCTs, may be related to the differences in the study findings.

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References

  1. Timothy M, Bahr RKO, Christensen RD. Treating preterm infants with erythropoietin does not increase the risk of retinopathy of prematurity. J Perinatol. 2024. https://doi.org/10.1038/s41372-024-02047-6.

  2. Ohls RK, Schibler KR, Lowe JR, Tan S, Beauman S, Grisby C, et al. Darbepoetin trial to improve red cell mass and neuroprotection in preterm infants. Oral Platform Pediatric Academic Societies Meeting, Washington DC E-PAS2023: 21504. 2023.

  3. Fukui K, Ito Y, Kokubo M, Nakanishi H, Hirano S, Kusuda S, et al. Erythropoietin and retinopathy of prematurity: a retrospective cohort study in Japan, 2008–2018. J Perinatol. 2024;44:886–91.

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Authors and Affiliations

  1. Division of Neonatology, National Center for Child Health and Development, Tokyo, Japan

    Kana Fukui, Yushi Ito & Tetsuya Isayama

  2. Department of Pediatrics, Graduate School of Medicine, Yokohama City University, Yokohama, Kanagawa, Japan

    Kana Fukui, Shuichi Ito & Tetsuya Isayama

  3. Division of Neonatology, Nagano Children’s Hospital, Nagano, Japan

    Masayo Kokubo

  4. Research and Development Center for New Medical Frontiers, Division of Neonatal Intensive Care Medicine, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan

    Hidehiko Nakanishi

  5. Department of Neonatal Medicine, Osaka Women’s and Children’s Hospital, Osaka, Japan

    Shinya Hirano

  6. Department of Pediatrics, Kyorin University, Tokyo, Japan

    Satoshi Kusuda

Authors
  1. Kana Fukui
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  2. Yushi Ito
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  3. Masayo Kokubo
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  4. Hidehiko Nakanishi
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  5. Shinya Hirano
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  6. Satoshi Kusuda
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  7. Shuichi Ito
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  8. Tetsuya Isayama
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Contributions

Kana Fukui and Tetsuya Isayama drafted the manuscript. Yushi Ito, Masayo Kokubo, Hidehiko Nakanishi, Shinya Hirano, Satoshi Kusuda, and Shuichi Ito critically reviewed and substantively revised the manuscript. All authors approved the final manuscript as submitted and agree to be accountable for the work.

Corresponding author

Correspondence to Tetsuya Isayama.

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Fukui, K., Ito, Y., Kokubo, M. et al. Is there a role for cohort studies after the publications of high-quality large RCTs on the association between erythropoietin and retinopathy of prematurity?. J Perinatol 45, 1029–1030 (2025). https://doi.org/10.1038/s41372-024-02055-6

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