Handbook on Vitamin A Tracer Dilution Methods to Assess Status and Evaluate Intervention Programs

HarvestPlus Technical Monographs are designed to provide a forum for HarvestPlus research outputs. Technical Monographs can be of two kinds: • state-of-the-art reviews that help to establish and define HarvestPlus research questions or • " gold standard " procedures to be followed in HarvestPlus research. HarvestPlus technical monographs are written by recognized experts in the field and are externally peer reviewed prior to publication. The vitamin A Tracer Task Force was initiated by IAEA, USAID, and HarvestPlus to prepare a series of three documents. The first on the appropriate use of vitamin A tracer (stable isotope) methods was published in 2004 by USAID/ILSI through the Micronutrient Global Leadership(MGL) project: handbook us the second Tracer Force Handbook and is being published as a HarvestPlus Technical Monograph. The third handbook will be on model-based estimates of absorption efficiency and will be published by the IAEA in 2005. Introduction 4 1|Description of the stable isotope dilution technique 5 1.1 Requirements for working with stable isotope labeled analogs of vitamin A 5 1.1.1 Facilities, equipment, and support 5 1.1.2 Personnel 5 1.2 Theoretical basis of the stable isotope dilution technique of vitamin A 5 1.3 Three-day stable isotope dilution procedure 6 1.4 Procedures for estimating total body vitamin A pool size 6 1.4.1 Choice of labeled vitamin A analog 7 1.4.2 Dose of labeled vitamin A 7 1.4.3 Preparation of labeled vitamin A doses 8 1.4.4 Administration of labeled vitamin A doses 8 1.4.5 Blood collection, processing, and transport procedures 9 1.5 Rationale for blood sampling times for measurement of plasma isotopic ratios of labeled to non-labeled retinol 9 1.6 Measurement of plasma isotopic ratios of labeled to non-labeled retinol 10 1.7 Factors that may affect plasma isotopic ratios of labeled to non-labeled retinol 10 1.8 Assessing adequacy of vitamin A status using the stable isotope dilution technique 11 2|Study protocols for using the paired stable isotope dilution technique 11 2.1 Site selection 11 2.2 Selection of study participants 11 2.3 Subject inclusion and exclusion criteria 12 2.4 Full study protocols for the paired stable isotope dilution technique 12 2.5 Partial study protocols for the paired stable isotope dilution technique 14 2.6 Estimation of duration of an intervention 17 2.7 Sample size calculation 18 2.8 Statistical analysis 18 3|Paired stable isotope dilution technique for estimating relative vitamin A equivalency factors for β-carotene