Reference values based on hospital admission laboratory data

Laboratory values taken from more than 13,000 newly admitted patients to the University of Alabama Hospital were analyzed using a percentile ranking system, and histograms for 24 laboratory tests were prepared. The percentile system is a better way to express test results than the classic normal range. The ability to correlate a test result with a clinical problem rises proportional to the degree of deviation from the midrange. Minor deviations frequently are without explanation, even after intensive clinical investigation. Invariably, great deviations are explainable. If one limits the interpretation of results to three ranges--abnormally low, abnormally high, and normal--much of the value of laboratory test interpretation is lost.