The D-dimer reference intervals in healty term newborns.

Objective: To determine the D-dimer reference intervals in the neonatal period.

Materials And Methods: The research had been carried out in the obstetrics and gynecology clinic and neonatal outpatient clinic of a third level hospital. Healthy term newborns aged between 1 and 28 days were enrolled in the study. Venous blood samples were collected from peripheral veins in all babies and D-dimer, prothrombin time, activated partial thromboplastin time and platelet counts were measured. Reference intervals for D-dimer in the neonatal period were determined using 2.5th and 97.5th percentile values.

Results: A hundred and thirty four newborns (71 boys, 63 girls) were enrolled in the study. Mean D-dimer levels of infants aged 1-28 days was 1.74 ± 1.88 mg/L (reference range; 0.25-2.81 mg/L). D-dimer levels were between 2.44 and 2.45 mg/L, 1.71-1.76 mg/L, 1.26-0.89 mg/L and 0.88-0.66 mg/L in the first, second, thirth and fourth week of life,respectively. D-dimer values inversely correlated with postnatal age (r:-0.3, p < 0.001). However, it remained above adult levels even in the last week. There was no statistically significant difference between the D-dimer levels of girls (1.93 ± 2.06 mg/L) and of boys (1.57 ± 1.71 mg/L).

Discussion: In this study, D-dimer levels in the neonatal period were found to be higher than adult levels stated in the literature. D-dimer levels gradually decreased overtime in the first month. It would be appropriate to use age-specific reference values in the evaluation of D dimer levels in the neonatal period.