Observations on the distribution of serum uric acid levels in participants of the Tecumseh, Michigan, Community Health Studies : A comparison of results of one method used at two different times and of two methods used simultaneously

Abstract

Individuals participating in the Tecumseh Community Health Study, in 1959-1960 (TCHS I) and 1962-1965 (TCHS II), had serum uric acid determinations by an enzymatic spectrophotometric method, SUA(ES), as part of a comprehensive health examination.Among the 1633 male and 1725 female subjects, the mean serum uric acid concentration had increased by 0.32 mg per 100 ml for males, and by 0.18 for females, over the the average of 4.1 yr between determinations. It was found that, approximately, 40 per cent of subjects had a decrease, and 56 per cent, an increase, in serum uric acid concentration. The change was greater than plus or minus 2.0 mg per 100 ml for 28.7 per cent of males and 19.4 per cent of females. Decreases of as much as 8.2, and increases of as much as 9.9 mg per 100 ml were observed. How much of the average increase, in an average 4.1 yr interval between tests, is due to ageing, except for males in the age range of 10-19 yr, is problematical. It seems probably that most of the average increase was due to technical factors in performance of the test.In the study of 1962-1965, serum uric acid determinations were done by two methods. An automated colorimetric method was compared with an enzymatic spectrophotometric method. Both methods showed the same types of distribution curves of serum uric acid concentrations and curves of age-sex specific mean serum uric acid.The values obtained by the automated colorimetric method were slightly, but, consistently, higher to a statistically significant degree than those of the enzymatic spectro-photometric method.For 2092 male subjects, the mean SUA(AC) was 0.21 mg per 100 ml greater than the mean SUA(ES), while for 2104 females subjects, this difference was 0.14.Of 4196 study subjects, whose sera were tested by both methods, about 90.0 per cent showed an agreement of the two values within +/- 0.9 mg per 100 ml. However, 1.9 per cent of males and 1.6 per cent of females, had ES values which exceeded AC values by 2.0 mg per 100 ml, while 2.8 per cent of male and 2.3 per cent of female subjects had AC values greater than ES values by 2.0 mg per 100 ml. The extremes of differences range from 4.4 to 7.3 mg per 100 ml.The data in this paper gives us increased confidence in the essential validity of the mean age and sex distributions of serum uric acid values, from the Tecumseh Community Health Studies, published in an earlier paper [2].It is concluded that, for the purposes of population studies, the automated colorimetric method is more advantageous than the enzymatic spectrophotometric method, because of its lesser cost.Comparison of the results of the two studies emphasizes the problems of definition of hyperuricemia. Further mathematical analysis of the distribution curves obtained in such studies may lead to definitions of normo- and hyperuricemia of greater precision for clinical purposes.