715
BRIEF REPORTS
Table 2.
proteins*
Correlations between serum uric acid (SUA) and serum
No. persons
tested
Correlation
coefficient
Probability?
Men
Women
Total
156
169
325
0.1697
0.1768
0.1300
0.05
0.05
0.02
Men
Women
Total
149
167
316
0.0905
0.1139
—0.0275
NS
NS
NS
0.1957
0.02
Total protein
Total globulin
Albumin
Men
151
Women
168
Total
319
0.1412
0.2541
0.05
0.01
* Outlying values (arbitrarily selected as a SUA >9.5 mg/dl for men
and >8.5 mg/d] for women) were excluded in this analysis.
+ NS = not significant.
of the U.S. population followed at BNL (4.4 + 0.5 SD
[n = 319], versus 4.7 + 0.4 SD, respectively), whereas
total globulin levels were higher in the Marshallese
(3.7 + 0.6 SD [n = 316], versus 2.6 + 0.7 SD).
Outlying values (arbitrarily selected as a SUA >9.5
me/d| for men and >8.5 mg/dl for women) were
excluded in these correlations because the purpose
was to study the effect of protein binding on normal
SUA in the general population.
Other findings included:
1) a significant correlation between SUA values and BMI (men: r = 0.230 [n = 110], P<
0.02; women: -r = 0.274 [n = 137], P <
0.01).
a significantly higher mean SUA value in
hypertensive subjects than in nonhypertensives (6.7 mg/dl [n = 32], versus 6.0 mg/dl
[n = 356], P = 0.02). When values of obese
individuals were removed, however, this
difference was lost (6.3 mg/dl [n = 16],
versus 6.0 mg/dl [n = 262], P = 0.54).
3) a lower mean SUA value in diabetic subjects than in nondiabetics, but the differ——
2
ence was not statistically significant (5.7
mg/dl [n = 35], versus 6.1 mg/dl [n = 353],
t = 1.48, df = 41, P = 0.15).
—
4) a difference in SUA values for men according to island of residence (f [3,175] = 3.03,
P = 0.03), with the population centers
having higher mean values than the remote
islands; for women, P = 0.09.
5 no significant difference, by one-way analysis of variance, between the groups ex-
posed to radiation and those not exposed
(Table 1).
Gout was present in 2 men at the time of SUA
testing, and 2 more developed clinical gout over the
ensuing 5 years, giving a current prevalence of 1.7%.
No patient had gouty tophi.
Discussion. Uric acid is tightly bound to an a,-
a-globulin, although only in small quantities (about
0.1-0.2 mg/dl) (9). Other protein binding is considered
to be loose, thus permitting glomerular filtration of
uric acid. The finding of a significant correlation
between SUA and albumin values suggests that albu-
min is one determinant of SUA levels. This is supported by in vitro studies indicating | gm/dl of albumin will
bind 0.6 mg/dl of uric acid (10). Data in this report also
show that the elevated globulin levels often encountered in tropical areas do not contribute significantly to
the SUA level, and thus do not explain the higher
values found in the Marshallese.
Anotherfactor influencing SUA is menopause,
at which time the SUA level increases (11). In the
present series, 67 of 196 women (34.2%) were over age
45. The mean SUA valuefor all women was5.6 mg/dl,
whereasthe value was 5.2 mg/dl for women =45 years
of age. This difference is reflected in the cumulative
frequency distribution (Figure 1).
The distributions of SUA values in these Micronesians were not bimodal, a point that has been noted
by others (2,4). Instead, the cumulative frequency
distributions, when graphed on probability paper,
were nearly straight lines for men and for women
under 46 years of age (Figure 1), suggesting that the
SUA distribution is Gaussian rather than leptokurtic
(12). It is therefore unnecessary, when selecting a
‘‘normal’’ range, to correct for skewness by using
percentile cutoffs. For Marshallese men the normal
range of SUA (based on the mean +2 SD) ts 4.0-9.2
mg/dl, and for women under 46 years of age, 2.8-7.6
mg/dl. The upper limits of normal are at least | mg/dl
higher than those reported in U.S. studies using nonenzymatic SUA assays.
A positive correlation between SUA values and
both body weight and ponderal index has been reported (13). The present data indicate a similar correlation
with another index of obesity, the BMI. The lack of
correlation of hypertension with SUA levels (after
deletion of values from obese persons), and the lower
mean SUA levels in diabetics than in nondiabetics has
been reported in other populations (14). While men
had higher SUA values in the population centers than
on the remote islands, we have insufficient data to