From Colleen Marinucci at Elmendorf AFB in Alaska:
Our pediatrician uses “The Harriet Lane Handbook: A Manual for Pediatric House Officers” for coagulation reference ranges and said 10.6-11.4 seconds is an age specific range for the prothrombin time. Our adult range is 10.7-14.3. Her four-yo patient resulted twice at 14.6 seconds and has a history of epistaxis. She felt this abnormal result warrented a mixing study.
Hi, Colleen. Thank you for your question. The Harriet Lane Handbook, which you will find in the lab coat pocket of every pediatric resident, and most clinical texts reference Andrew M, Vegh P, Johnston M. et al: Maturation of the Hemostatic System During Childhood. Blood 1992; 80: 1998-2005, seminal research directed by the late Maureen Andrew, and available from the American Society of Hematology as a free download. According to Andrew, 10.6 to 11.4 seconds is the correct reference interval for a four year old, so your pediatrician is correct to pursue follow-up studies. I hope this is helpful. Geo