Seasonal and meteorological associations of vitamin K-dependent coagulation factors in 1-month-old infants: assessment of Normotest values

We aimed to determine the presence of seasonal and meteorological associations of the activity of vitamin K-dependent coagulation factors to explain the seasonal variation in vitamin K deficiency-related bleeding. Seasonal and monthly changes in Normotest values in 1759 healthy 1-month-old infants were retrospectively accessed, and the impact of meteorological parameters on Normotest values was analyzed. Normotest values peaked in winter and were the lowest in summer, with statistically significant differences among the seasonal values (P < 0.001). Comparing monthly variations, the values peaked in January and were the lowest in August (P < 0.001). Only the average daily air temperature significantly correlated with the Normotest values on multiple linear regression (P < 0.001) and with low Normotest values on multiple logistic regression analysis (odds ratio, 1.023;P = 0.002). Seasonal and monthly variations in Normotest values were observed in 1-month-old infants, possibly due to fluctuations in daily air temperature.