International normalized ratio testing with a point-of-care coagulometer in 1-month-old infants: A comparison with Normotest.

INTRODUCTION: Early infants are at risk of vitamin K (VK) deficiency-associated bleeding unless they receive VK prophylaxis. A coagulation screening test might be necessary to detect prophylactic failure, but it is rarely conducted owing to the difficulty of blood sampling. CoaguChek XS is a portable, point-of-care (POC) coagulation analyzer that determines international normalized ratios (INRs) using only small volumes of blood. Although POC tests assessing INR have become widespread for adults, studies have not been performed in early infancy. This study aimed to determine the reference interval (RI) for INR for 1-month-old infants using the CoaguChek XS and to compare INRs with Normotest (NT) values to evaluate its efficacy as a VK deficiency screening test.

MATERIALS AND METHODS: This study included 578 consecutive 1-month-old, healthy, term infants who underwent a 1-month health checkup. CoaguChek XS INRs and NT values were analyzed for each subject.

RESULTS: The enrolled neonates were orally administered VK 6-12h and 4days after birth. An INR RI for 1-month-old infants was established using the CoaguChek XS (range of 0.9-1.1). On the other hand, the NT RI was 69%-130%. We observed a significant inverse correlation between INRs and NT values.

CONCLUSIONS: Our study is the first to establish an INR RI using the CoaguChek XS for 1-month-old, healthy, term infants. CoaguChek XS INR was more convenient to test than NT. However, we could not demonstrate its efficacy as a VK deficiency screening test because no infant had an aberrant NT value or a bleeding disorder.