Your vascular laboratory has 38 lower extremity venous duple…

Yоur vаsculаr lаbоratоry has 38 lower extremity venous duplex exams that had a subsequent venogram for a variety of reasons.  Of these, both tests documented venous disease in 22 extremities, and ruled out venous disease in 10.  In 4 cases, the venous imaging study was considered normal while venography documented disease.  There were 2 situations where the duplex study was interpreted as abnormal, but no disease was evident on venography.   What is the overall accuracy?