Measuring the glycemic index of foods: interlaboratory study

Many laboratories offer glycemic index (GI) services. We assessed the performance of the method used to measure GI. The GI of cheese-puffs and fruit-leather (centrally provided) was measured in 28 laboratories (n = 311 subjects) by using the FAO/WHO method. The laboratories reported the results of t...

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Bibliographic Details
Published in:	The American journal of clinical nutrition Vol. 87; no. 1; pp. 247S - 257S
Main Authors:	Wolever, Thomas MS, Brand-Miller, Jennie C, Abernethy, John, Astrup, Arne, Atkinson, Fiona, Axelsen, Mette, Björck, Inger, Brighenti, Furio, Brown, Rachel, Brynes, Audrey, Casiraghi, M Cristina, Cazaubiel, Murielle, Dahlqvist, Linda, Delport, Elizabeth, Denyer, Gareth S, Erba, Daniela, Frost, Gary, Granfeldt, Yvonne, Hampton, Shelagh, Hart, Valerie A, Hätönen, Katja A, Henry, C Jeya, Hertzler, Steve, Hull, Sarah, Jerling, Johann, Johnston, Kelly L, Lightowler, Helen, Mann, Neil, Morgan, Linda, Panlasigui, Leonora N, Pelkman, Christine, Perry, Tracy, Pfeiffer, Andreas FH, Pieters, Marlien, Dan Ramdath, D, Ramsingh, Rayna T, Robert, S Daniel, Robinson, Carol, Sarkkinen, Essi, Scazzina, Francesca, Sison, Dave Clark D, Sloth, Birgitte, Staniforth, Jane, Tapola, Niina, Valsta, Liisa M, Verkooijen, Inge, Weickert, Martin O, Weseler, Antje R, Wilkie, Paul, Zhang, Jian
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 01-01-2008 American Society for Nutrition American Society for Clinical Nutrition, Inc
Subjects:	Adolescent Adult Aged Area Under Curve Blood Glucose Blood Glucose - metabolism Carbohydrates cheese puffs classification Clinical Laboratory Techniques - standards Clinical Medicine Clinical trial Clinical trials Cross-Over Studies Diet dietary carbohydrate Dietary Carbohydrates Dietary Carbohydrates - metabolism Endocrinology and Diabetes Endokrinologi och diabetes equipment performance Female Food Food - classification Food Analysis Food Analysis - standards food composition fruit leather Glucose Glucose Tolerance Test Glycemic Index Health Sciences Humans Hälsovetenskap Klinisk medicin laboratories Laboratory Techniques and Procedures Male MEDICAL AND HEALTH SCIENCES MEDICIN OCH HÄLSOVETENSKAP men metabolism methodology Middle Aged Nutrition Nutrition and Dietetics Näringslära precision Reference Values Reproducibility of Results Sensitivity and Specificity women glycemic index Clinical trial glucose dietary carbohydrate humans methodology
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Summary:	Many laboratories offer glycemic index (GI) services. We assessed the performance of the method used to measure GI. The GI of cheese-puffs and fruit-leather (centrally provided) was measured in 28 laboratories (n = 311 subjects) by using the FAO/WHO method. The laboratories reported the results of their calculations and sent the raw data for recalculation centrally. Values for the incremental area under the curve (AUC) reported by 54% of the laboratories differed from central calculations. Because of this and other differences in data analysis, 19% of reported food GI values differed by >5 units from those calculated centrally. GI values in individual subjects were unrelated to age, sex, ethnicity, body mass index, or AUC but were negatively related to within-individual variation (P = 0.033) expressed as the CV of the AUC for repeated reference food tests (refCV). The between-laboratory GI values (mean ± SD) for cheese-puffs and fruit-leather were 74.3 ± 10.5 and 33.2 ± 7.2, respectively. The mean laboratory GI was related to refCV (P = 0.003) and the type of restrictions on alcohol consumption before the test (P = 0.006, r2 = 0.509 for model). The within-laboratory SD of GI was related to refCV (P < 0.001), the glucose analysis method (P = 0.010), whether glucose measures were duplicated (P = 0.008), and restrictions on dinner the night before (P = 0.013, r2 = 0.810 for model). The between-laboratory SD of the GI values is ≈9. Standardized data analysis and low within-subject variation (refCV < 30%) are required for accuracy. The results suggest that common misconceptions exist about which factors do and do not need to be controlled to improve precision. Controlled studies and cost-benefit analyses are needed to optimize GI methodology. The trial was registered at clinicaltrials.gov as NCT00260858.
Bibliography:	http://www.ajcn.org/contents-by-date.0.shtml
ISSN:	0002-9165 1938-3207 1938-3207
DOI:	10.1093/ajcn/87.1.247S