<prompt> A child with prolonged aPTT underwent laparotomy and still did not develop any bleeding complications. Which of the following clotting factors is most likely to be deficient?Factor VIIFactor XllFactor XFactor XIII  <response>: Ref: Nelson Textbook of Pediatrics, 18th editionExplanation:The dual mechanisms of activating clotting areA. Intrinsic - Surface activation -Measured by aPTTB. Extrinsic - Tissue factor mediated - Measured by PT Deficiency of contact factors like Factor XII. prekallikrein HMW Kininogen causes prolonged aPTT but no bleeding symptoms. See the following table Coagulation profile in common hematological conditionsDiseaseProthrombintimePTPartialthromboplastin lime aPTTBleedingtimePlateletcountBernard-Soulier syndromeUraffectedUnaffectedProlongedDecreased or unaffectedDisseminated intravascular coagulationProlongedProlongedProlongedDecreasedFactor XII deficiencyUnaffectedProlongedUnaffectedUnaffectedFactor V deficiencyProlongedProlongedUnaffectedUnaffectedFactor X deficiencyProlongedProlongedUnaffectedUnaffectedGlanzmannsthrombastheniaUnaffectedUnaffectedProlongedUnaffectedHemophiliaUnaffectedProlongedUnaffectedUnaffectedLiver failure, earlyProlongedUnaffectedUnaffectedUnaffectedLiver failure end-stageProlongedProlongedProlongedDecreasedThrombocytopeniaUnaffectedUnaffectedProlongedDecreasedUremiaUnaffectedUnaffectedProlongedUnaffectedVitamin K deficiency or warfarin TherapyProlongedNormal or mildly prolongedUnaffectedUnaffectedVon Willebrand diseaseUnaffectedProlongedProlongedDecreased 