Laboratory coagulation parameters in extremely premature infants born earlier than 27 gestational weeks upon...

Few published data exist to guide interpretation of coagulation times in extremely premature infants.

To determine coagulation reference ranges on day 1 of life in extremely premature infants.

A retrospective review of day 1 coagulation tests was performed in 144 infants <27 weeks' gestation between 2004 and 2010 in a tertiary neonatal unit. Samples were drawn through a non-heparinized umbilical or peripheral venous catheter as part of routine clinical care.

Mean (SD) and median (range) prothrombin times (PT) of 21.5 (5.3) and 20.2 (13.3-39) s, respectively, activated partial thromboplastin times (APTT) of 75.2 (27.8) and 67.4 (34.9-191.6) s, respectively, and plasma fibrinogen levels of 1.9 (1.1) and 1.4 (0.5-4.8) g/l, respectively, were reported. Using reference intervals derived from the 2.5th to 97.5th centiles, ranges of 14.4-36.7 s, 40.5-158.5 s and 0.7-4.8 g/l were determined for PT, APTT and plasma fibrinogen levels, respectively. In a subcohort with grade 0-2 intraventricular haemorrhage (n = 92), mean PT and APTT were 20.9 and 71.3 s, respectively, versus mean PT and APTT of 23.1 and 88.4 s (p = 0.06 and p = 0.03), respectively for those with grade 3-4 intraventricular haemorrhage. Mean PT and APTT in a cohort of infants defined to be small for gestational age were 22 and 76.8 s. These results did not differ significantly from non-small for gestational age infants, with a mean PT and APTT of 19.5 and 73.4 s (p = 0.09 and p = 0.7).

Reference ranges based on retrospective data were determined for PT, APTT and fibrinogen in a large cohort of extremely preterm infants.