In vitro undetectable PT and Fibrinogen (and in vivo?)

A 81 aged woman came to E.R. of Trieste University Hospital with a traumatic head injury. Blood cells count, liver enzymes and other parameters were normal, but with a photometric clot detection method PT and PT-derived Fibrinogen were undetectable, Fibrinogen-Clauss gave different results (157 to 357 mg/dL) and aPTT-Ratio was normal (0.96). When the instrument detection performance was improved, PT was normal and PT-derived Fibrinogen detectable, but Fibrinogen-Clauss was still very unsteady (352/294/558 mg/dL). When a mixing test was performed with normal pool plasma, PT was corrected, PT-derived Fibrinogen was very low (80 mg/dL) and Fibrinogen-Clauss resulted 360 mg/dL. Fibrinogen-Antigen was 368 mg/dL by a nephelometric immunoassay. In another Lab with a different optical analyzer, PT and aPTT yielded the same results, Fibrinogen-Clauss was 557 mg/dL with 35 IU/ml Thrombin reagent (and a very steep clot formation curve), but 113 mg/dL with 15 IU/ml Thrombin reagent (and a normal curve). With an electromechanical clot detection method, PT-INR and aPTT-Ratio were normal (0.88 and 0.96 respectively), Fibrinogen-Clauss was normal (400 mg/dL) but unsteady. However in a few days our patient healed up perfectly; she declared that her sister had the same performance when she was referred to another Hospital for a check-up, nonetheless they never had any severe bleeding in their life. Samples from our patient’s son and daughter were taken and resulted completely normal for coagulation tests. We hypothetized: 1) a too fast Thrombin formation and/or Fibrinogen consumption, as shown by steep coagulation curves without a stable plateau; 2) an excessive thrombin formation, (in preliminary studies, however, G20210A mutation was absent and F1+2 were normal); 3) a dysfibrinogenemia, (to be studied). Further studies for Endogenous Thrombin Potential about thrombin ipothesis and for genetical pattern about fibrinogen molecule are needed to clarify this case.