Pakdeeto S.Mahidol University2023-06-202023-06-202022-01-01Journal of Perinatology Vol.42 No.1 (2022) , 116-12007438346https://repository.li.mahidol.ac.th/handle/20.500.14594/87443Objectives: We constructed reference intervals for end-tidal carbon monoxide (ETCOc) levels of neonates 28 0/7 to 34 6/7 weeks gestation in order to assess hemolytic rate. Study design: This is a prospective four-NICU study in Bangkok, Thailand, and Utah, USA. Results: Of 226 attempted measurements, 92% were successful. Values from day 1 through 28 were charted and upper (>95th percentile) reference interval limits calculated. During the entire 28 days, the ETCOc upper reference intervals from babies in Bangkok were higher than those in Utah (p < 0.01). No differences were found due to sex, or earliest vs. latest gestation at birth (both p > 0.1). Similar to term neonates, preterm neonates in Bangkok and Utah had higher ETCOc values during the first 48 h after birth than thereafter (p < 0.01). Conclusions: Using this methodology, and the reference interval chart, the hemolytic rate of preterm infants ≥28 weeks can be assessed.MedicineArticleSCOPUS10.1038/s41372-021-01207-22-s2.0-851154175611476554334556800