In three later studies, vitamin B1 deficiency was measured using various measures in blood: the thiamine pyrophosphate (TTP) effect [13], the erythrocyte thiamine level [22], and the thiamine diphosphate (TDP) effect [16] and transketolase activity (TK activity) [13] and these studies used varied techniques and instruments for these measurements (Table 2). The gene discussed is TKT; the disease is beriberi.