Analyte stability during the total testing process: studies of vitamins A, D and E by LC MS/MS
Abstract Background: There are limited evidence based studies demonstrating the stability of fat soluble vitamins (FSV) measured in blood. This study aimed to examine the effects of light, temperature and time on vitamins A, D and E throughout the total testing process. Methods: Four experiments were conducted. Three investigated the sample matrix, of whole blood, serum and the extracted sample, against the variables of temperature and light; and the fourth experiment investigated the sample during the extraction process against the variable of light. All samples were analysed via our simultaneous FSV method using liquid chromatography tandem mass spectrometry technology. The allowable clinical percentage change was calculated based on biological variation and desirable method imprecision for each analyte. The total change limit was 7.3% for 25 OH vitamin D3, 11.8% for retinol and 10.8% for a tocopherol. Results: Vitamins D and E were stable in the investigated conditions (concentration changes <4% in the pre analytical and analytical stages. Vitamin A showed photosensitivity in times >48 h with concentration changes of 6.8% (blood) and 6.5% (serum) both are within the allowable clinical percentage change. By contrast, the extracted retinol sample demonstrated a concentration change of 18.4% after 48 h of light exposure. However, vitamin A in the serum and extracted solution was stable for one month when stored at 20degC. Conclusions: Blood samples for vitamins D and E analyses can be processed in normal laboratory conditions of lighting and temperature. The required conditions for vitamin A analysis are similar when performed within 48 h. For longer term storage, serum and vitamin A extracts should be stored at 20degC.
Clinical chemistry and laboratory medicine