Coagulation standards in healthy newborns and infants

Abstract

BackgroundThe range of normal values for coagulation factors in the healthy newborn was described 30 years ago but since then the reagents, automated systems, and dosing techniques have changed considerably. For 30 years, several authors have tried to update the standards and references in children using updated reagents but the newborn and infant population in these studies has been quite small, limiting the findings. The aim of this study was to establish the normal coagulation standards in healthy newborns. MethodsWe included all consecutive healthy newborns with pyloric stenosis presenting to our reference center over a period of 5 years. We calculated the reference ranges defined as mean±2 SD. Normality of distribution was checked graphically and by using the Shapiro–Wilk test. Correlations between two continuous variables were assessed using Spearman's rank coefficient correlation. Statistical testing was done at the two-tailed α-level of 0.05. Data were analyzed using the SAS software package, release 9.4 (SAS Institute, Cary, NC). ResultsWe included 112 healthy newborns and infants. The median age was 35.5 days (15.0–88.0), median weight was 4062g (2855–6040), and 90.2% were boys. Activated partial thromboplastin time (aPTT) and prothrombin time (PT) were not correlated with age (P=0.92 and P=0.21, respectively) or with weight (P=0.16 and P=0.90, respectively). The reference range was 28.6–46.2 s for aPTT, 0.91–1.49 for aPTT ratio, and 71.3–110.6 s for PT. Regarding fibrinogen (n=24), the median was 2.2g/L (1.2–3.2); the median for factor II was 67.0U/dL (51.0–130.0; n=20), and 101.5U/dL for factor V (68.0–233.0; n=20). Regarding factor VIII, the median was 75.0U/dL (45.0–152.0; n=25), 49.0U/dL for factor IX (32.0–96.0; n=25) and 53.0U/dL (29.0–112.0) for factor XI (n=23). ConclusionThis study can help to establish standards for coagulation testing in this very specific population. Indeed, our study represents the largest newborn population in a recent investigation of PT and aPTT using updated reagents.