Accurate reference intervals established in healthy subjects are essential for appropriate interpretation of laboratory test results and to assist clinicians in diagnosis, monitoring, and treatment of disease. These values are affected by key covariates including age, sex, race, geographical location and dietary pattern. Reference intervals are defined as “limiting values within which a specified percentage (usually 95%) of apparently healthy individuals’ results would fall” i.e. usually the 2.5th and 97.5th percentiles of the test result distribution in the reference (healthy) population.