THE NORMAL RANGE OF PLASMA URATE LEVELS

Abstract

SUMMARYThe plasma levels of urate were determined in a group of apparently healthy young subjects, 100 being males and 100 females, none of whom had a family history of gout or evidence of renal disease. The results in the males appeared to have a bimodal distribution, suggesting that they might represent two populations, one normal and the other hyperuricæmic. Although there was no sharp dividing line, the plasma urate levels for these two groups seemed to separate at a value of about 7·0 mg. per 100 ml. The results in females approximated more to a normal distribution, and only one result exceeded 5·7 mg. per 100 ml. If, on the other hand, the value which excluded the upper 5% of results was calculated from the mean and standard deviation (the requirement being disregarded that the distribution should be a normal one for this to apply), results almost identical with those already chosen would be obtained.These findings have therefore suggested that values of 7·0 mg. per 100 ml. for males and 5·7 mg. per 100 ml. for females be taken as the upper limits for the normal plasma urate level estimated by the colorimetric method. A uricase method of estimation produced results which were about 0.2 mg. per 100 ml. lower than those produced by this colorimetric method. As the distribution of the results for males could also be interpreted as being a normal curve skewed towards the higher values, it is considered that much larger numbers than these would be needed to allow any conclusions to be drawn concerning the theories of inheritance of the plasma urate level.