Coagulation Case Study
Michael Laposata, MD, PhD
Elizabeth M. Van Cott, MD
Figure 1 | Figure 2 | Figure
3 | Figure 4 | Figure 5
| Figure 6
This is the fifth in a periodic series of articles written
by members of the CAP Coagulation Resource Committee and focusing
on laboratory evaluation of coagulation disorders.
A 28-year-old man was repairing a sink in his home when he became
acutely short of breath. He was taken to the emergency room, where
medical personnel established a diagnosis of pulmonary embolism.
Two years earlier, the patient had suffered a deep vein thrombosis
and was anticoagulated with warfarin for six months. He was evaluated
around the time of his deep vein thrombosis and found to have normal
values for what his primary care physician believed was the full
battery of laboratory tests appropriate for identifying acquired
or congenital hypercoagulation risk factors. However, the patient
was tested only for antiphospholipid antibodies, protein C, protein
S, and antithrombin. He was not evaluated for factor V Leiden, the
prothrombin G20210A mutation, or homocysteine. Because the patient’s
antiphospholipid antibody tests and protein C, protein S, and antithrombin
levels were normal, his physician terminated his Coumadin therapy
at six months, in accordance with published guidelines for treating
a spontaneous venous clot in the absence of identifiable risk factors.1
After his second thrombotic event (the pulmonary embolism), the
patient was referred to our practice for further evaluation. We
tested for activated protein C resistance, the prothrombin G20210A
mutation, and obtained a homocysteine level. In this evaluation,
the patient was found to be heterozygous for the prothrombin G20210A
mutation and heterozygous for factor V Leiden and had no evidence
The published recommendation for patients with one spontaneous
thrombosis and a congenital risk factor (such as factor V Leiden
in combination with the prothrombin G20210A mutation) is lifelong
warfarin therapy.1 Had the warfarin not
been discontinued after his first thrombotic event, the second,
more life-threatening clot may have been prevented.
Primary care physicians are now confronted with an array of new diagnostic
tests at a faster rate than ever before, particularly in the area of thrombophilia.
This poses an educational challenge to physicians. Featured in this area are
six algorithms for selecting and interpreting tests that lead to a diagnosis
of activated protein C resistance, the prothrombin G20210A mutation, hyperhomocysteinemia,
protein C deficiency, protein S deficiency, and antithrombin deficiency. (Antiphospholipid
antibodies were the focus of the coagulation case study published in the March
1999 issue of CAP TODAY, page 84.) These flowcharts are evolving rapidly. They
represent one current approach to diagnosing hypercoagulable states associated
with these six laboratory abnormalities. The current case illustrates the diagnosis
of two of the more common risk factors for thrombosis. Future coagulation case
studies published as part of this series will refer to the diagnostic algorithms
in this article.
1. Fifth ACCP Consensus Conference on Antithrombotic Therapy. Hyers TM, Agnelli G, Hull RD, et al. Antithrombotic therapy for venous thromboembolic disease. Chest. 1998;114:561S578S.
Dr. Laposata is director of clinical laboratories, Massachusetts
General Hospital, Boston. He is a member of the CAP Coagulation Resource Committee.
Dr. Van Cott is director of the coagulation laboratory, Massachusetts General