<prompt> Feature of hemorrhagic disease of new born is?Prolonged prothrombin timeDefective platelet countProlonged bleeding timeProlonged thrombin time  <response>: Answer is A Prolonged prothrombin time Hemorrhagic disease of new born results from a deficiency of vitamin K. Prothrombin time is the single best laboratory test to detect vitamin K deficiency as vitamin k deficiency may present with isolated prolongation of PT Laboratory features of vitamin k deficiency CMDT-2008 Both PT and PTT are prolonged but prolongation of PT is a more sensitive test to detect vitamin K deficiency than PTT - The PT is prolonged to a greater extent than PTT - With mild vitamin K deficiency only the PT is defective Fibrinogen level, Thrombin time and platlet count are not affected - CMDT 