Hello In the population surveys we have done we used two methods: (1) measurement of serum retinol after collection of a peripheral (fingerstick) blood sample. (2) measurement of RBP on dried blood spots. In my opinion, the first is the more direct and reliable approach, but there may be times where cold chain and other conditions make dried blood spot analysis the best or only choice. I have not had any direct experience of using the iCHECK FLUORO but I understand that this is a new technology for the measurement of vitamin A and other micronutrients in food - not in people. Hope this helps a bit.

From Bradley Woodruff: Andy, thanks for the information. The website for the company which makes the iCheck FLOURO system (BioAnalyt GmbH) states that this method is for the "determination of vitamin A in fortified food such as flour, sugar, premix and biological fluids" so it seems that the manufacturer is aiming at the clinical testing market as well as the fortification monitoring market. Furthermore, the website states "iCheck™ determines the exact level of vitamin A. It is equally reliable as the HPLC reference method" but there is no citation of empirical evidence supporting this claim when measuring vitamin A in human blood or blood fluids. A year ago, in response to my e-mail inquiry, the Managing Director said that validation results would be presented at the Asian Congress of Nutrition in May 2011. I did not attend this conference nor have I heard anything about these results. The only study I can currently find which directly compares blood vitamin A measurement using a standard method, such as HPLC, to iCheck Flouro is a study of whole blood from cows. This publication can be downloaded from the company's website (http://www.bioanalyt.com/company/publications). Regarding ease of use, the instructions on the website show a process which is more complicated than something really simple, like HemoCue, but still possible to do in the field. I have been completely unable to find anything about the cost of these kits. I cannot locate a retailer on the web. Considering that this kit has been available since October 2010, I don't understand this complete lack of information about distribution or sale. My impression is that this new method shows potential, but really needs to be validated in human blood and in real-life conditions. So if anyone has enough spare money to buy one of these kits and take it out on their next survey measuring vitamin A status, please let us know the results you get!

According to my own experience HPLC is the best method known so far, I used it personally during my research on Vitamin A assessment in Smokers. These kits reliability is under question due to high variation in the result from sample to sample and withing the same sample (Repetition).