The reticulocyte production index (RPI) may not adequately measure bone marrow erythropoietic capacity in the pediatric population, according to research published in the American Journal of Clinical Pathology.

Analysis of reticulocytes is a common and cost-effective resource for guiding anemia diagnosis and evaluating anemia etiology. The RPI, developed in 1969, is widely used for evaluating the response capacity of bone marrow in anemia, though the index was developed using data only from adult patients. Given that hematological values vary by age in the pediatric population, RPI usefulness in children is still unestablished.

Researchers conducted a retrospective, observational, and analytical analysis to determine whether the use of the RPI adjusting for normative hematologic values in the pediatric population is as equally reliable as the RPI used among adults, and whether differences between the standard RPI model and the adjusted model had a clinical effect on anemia diagnosis. Of 10,724 validated examinations, 5503 met the criteria for the study. All patients were between the ages 0 and 18 years.

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Between the standard 1969 model and the adjusted model used for pediatric patients in this study, no significant systematic error was found. In addition, agreement between the standard RPI and adjusted scores was not found for any age.

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A significant difference in the proportion of regenerative vs arregenerative cases of anemia was reported between patients aged 1 month to 12 years who were boys and patients aged 1 month to 18 years who were girls.

“For pediatric patients, the RPI is not an adequate tool for evaluating the response of the bone marrow in the presence of anemia due to differences in hematologic values between children and adults and the absence of information on the maturation time of reticulocytes in children,” the authors wrote.


Bracho FJ, Osorio IA. Evaluation of the reticulocyte production index in the pediatric population [published online April 9, 2020]. Am J Clin Pathol. doi: 10.1093/ajcp/aqaa020