Diagnosis of vitamin B1 deficiency is made by

Diagnosis of Vit B1 deficiency is made by Transketolase activity.Biochemical Parameters In thiamine deficiency, blood thiamine is reduced, but pyruvate, alpha-ketoglutarate and lactate are increased. Erythrocyte transketolase activity is reduced; this is the earliest manifestation seen even before clinical disturbances.Reference: Textbook of Biochemistry by D M Vasudevan, sixth edition pg no. 392