<prompt> Which of the following shows functional assessment of B1 deficiency:RBC TransketolaseRBC Glutathione reductaseSerum Thiamine levelsRBC Glutathione Peroxidase  <response>: Ans. a RBC TransketolaseRef: Harpers Biochemistry 30th Ed; Page No- 556Biochemical assessment of Thiamin nutritional status done by erythrocyte transketolase activation. The activation of apo-transketolase the enzyme protein in erythrocyte lysate by thiamin diphosphate added in vitro has become the accepted index of thiamin nutritional status.Functional Assessment of Vitamin B complexVitamin B complexBiochemical assessmentThiamine B1Erythrocyte transketolase activity is reduced.Riboflavin B2Measurement of activation of Erythrocyte Glutathione Reductase by FAD added in vitro.Pyridoxine B6 Erythrocyte Transaminase activity Tryptophan load test-measurement of Xanthurenic acid following Tryptophan load.Folic Acid B9 Serum folate Serum Homocysteine Histidine Load test or FIGLU excretion test Peripheral Blood smear Macrocytes , tear drop cells, hypersegmented neutrophils, anisopoikilocytosis Red cell folate AICAR Amino Imidazole Carboxamide Ribose 45 phosphate Excretion TestCobalamin B12 Serum Homocysteine Serum Cobalamin Schilling Test using radioactive labelled coablt-60 Serum Methyl Malonate Urine Homocysteine and MMA Bone marrow and Peripheral blood smear 