A stimulation of greater than 16% has been taken as a thiamin deficiency. K.S.J., D.A.P., and A.K. METHODS: Baseline erythrocyte transketolase activities were measured on blood samples collected from 36 chronic alcoholic patients presenting acutely to the Accident and Emergency department. The transketolase method is an indirect assessment. Testing may be indicated in suspected alcoholic or nutritional cardiomyopathy or neuropathy and in Wernicke-Korsakoff syndrome. Patients received either intravenous Pabrinex (thiamine) supplemented with magnesium sulphate (n = 18) or Pabrinex only (n = 18). Slope (95% CI) = 0.88 (0.37–1.39); intercept (95% CI) = 0.26 (−0.44 to 0.68). The concentration of total thiamin (free thiamin plus its phosphate esters in whole blood) is 60–120 μg/L, with 90% of the vitamin in erythrocytes and leukocytes. Reference ranges: B1 (Thiamine) 1.15 normal, 1.15 - 1.25 borderline, >1.25 deficient Results expressed as ratio of activated to basal activity in IU/gHb. L.J.C. In this paper, we provide a detailed protocol for the measurement of ETK activity that can be used as a foundation for assay harmonization. Results: The method was linear to at least 200 microgram/L. Open circles, observed data points; solid line, regression line; dashed line, line of equality. File S1. Learn about our remote access options, NIHR BRC Nutritional Biomarker Laboratory, MRC Epidemiology Unit, University of Cambridge, Cambridge, UK, Address for correspondence: Kerry S. Jones, NIHR BRC Nutritional Biomarker Laboratory, MRC Epidemiology Unit, University of Cambridge, Clifford Allbutt Building, Cambridge Biomedical Campus, Hills Road, Cambridge CB2 0AH, UK. Traditionally the erythrocyte transketolase saturation test, which is a measure of the stimulation of the transketolase reaction, has been used to assess thiamin status. An erythrocyte transketolase isoenzyme pattern associated with the Wernicke-Korsakoff syndrome. ... this test is now considered obsolete. Some of the experimental work was performed at the MRC Elsie Widdowson Laboratory, Cambridge, UK, which closed in December 2018. TRANSKETOLASE IN ERYTHROCYTES 381 0.01 ml GDH-TIM and 0.05 ml NADH. Indirect: spectrophotometric assay of red cell transketolase with and without added thiamin pyrophosphate. Improvements in harmonization will also provide opportunity for investigating outstanding questions related to thiamine physiology and EKTAC assays, including the establishment of cutoffs for deficiency, characterizing agreement with other markers of thiamine status (e.g., ThDP), and to better understand conditions where interpretation of ETKAC may be confounded. However, other studies posit that the decrease in apo‐transketolase is a response to thiamine deficiency.17, 38 Either way, chronic thiamine deficiency may cause loss of apo‐transketolase and evidence suggests that this is caused by an effect on synthesis rather than catabolism of transketolase.39 The impact of this effect on interpretation of the EKTAC is, however, uncertain. Deming regression of ETKAC measured in erythrocyte hemolysates prepared from LH and EDTA whole blood collected from 15 adults and processed within 2 h of collection or after refrigeration for 24 hours. The measurement of serum or plasma thiamine concentration is of limited use since it represents only a small portion of thiamine in the blood and is affected by a number of disease states.1 Although a correlation between plasma thiamine and erythrocyte ThDP has been shown,4 these data were from a thiamine fortification trial; plasma thiamine is affected by recent dietary intake and is, therefore, not suitable as a biomarker of long‐term thiamine status. In conjunction with whole blood or erythrocyte transketolase activity preloading and postloading, a thiamine loading test is the best indicator of thiamine deficiency. Plate map for the ETKAC analysis. Genetic differences leading to different transketolase isoforms that may have different activities or stabilities30 or be associated with the manifestation of thiamine deficiency in Wernicke–Korsakoff syndrome have been suggested.30, 31 However, other studies have found no evidence for isoforms or disease associations and suggest that earlier observations were due to the methodologies used.32-36. 1). Perceived limitations of the assay include relatively poor precision, lack of standardization, instability of the transketolase enzyme, and lack of consensus about cutoffs for deficiency.42 However, these limitations equally apply to other assays of thiamine status, such as whole blood ThDP. In thiamine insufficiency or deficiency, the addition of exogenous ThDP has a progressively greater effect on ETKAC, which provides a continuum of thiamine status.13, Although there is no international consensus on cutoffs, the commonly used threshold for risk of deficiency is an ETKAC of >1.25.13, 14 An ETKAC of <1.15 indicates sufficiency and values between 1.15 and 1.25 suggest a low risk of clinical deficiency.13 Others have suggested values of ≥1.2 indicate deficiency.15 Beriberi is typically associated with ETKAC values >1.4.2, The use of ETKAC rather than absolute measures of ETK activity is preferred for three main reasons: (1) the between‐subject variation in basal activity is large; (2) it is assumed, but not certain, that apoenzyme levels are not affected by vitamin deficiencies;5 and (3) it reduces the need for the precise definition of assay conditions (e.g., optical path length), which are critical to calculate absolute enzyme activities.16 Others have suggested using combinations of the stimulated ETK activity and the ETKAC in interpretation.17. Transketolase activity was measured in the erythrocyte haemolysates of 14 patients with chronic uraemia and in 16 healthy controls in the presence of TPP and following TPP saturation. The authors declare no competing interests. Green (lithium heparin)- must reach the lab within 24 hours of collection. ETKAC has advantages over methods for the direct measurement of ThDP, including relative ease and the requirement for less specialized equipment, making the assay potentially more affordable and sustainable. LabCorp test details for Red Blood Cell (RBC) Antigen Typing: E/e ... Red Blood Cell (RBC) Antigen Typing: E/e. Erythrocyte transketolase activity measured on the Gemstardiscrete analyser J. E. Buttery, B. R. Chamberlainand C. R. Milner Department: ofClinical Chemistry, TheQueenElizabeth Hospital, Woodville, South Australia 5011, Australia Introduction TheNADH-dependentmethod ofSmeets et al.