Enzyme activity measured in beri-beri is: (A) Transketolase, (B) Transaminase, (C) Decarboxylase, (D) Deaminases
Answer is A. The transketolase activity in erythrocytes  is decreased. MeasuremenL of  RBC transketolase activity is  a  reliable diagnostic test to  assess thiamine deficiency.
Ref: Satyanarayana, 3rd ed, pg-136