2024 Volume 48 Issue 1 Pages 33-40
Japanese guidelines for the treatment of hyperuricemia and gout recommend a 60-minute clearance test to determine the type classification of hyperuricemia; however, the current judgment method may determine the type classification as the uric acid underexcretion type even if uric acid clearance (uric acid excretion ability) has not decreased. When examining the results of clearance tests conducted on 2,272 patients with gout, 22 were classified as the uric acid underexcretion type even though uric acid clearance had not decreased. Such cases should not be classified as the uric acid underexcretion type, and diagnosis of the uric acid underexcretion type should be determined when urinary uric acid excretion is 0.51 mg/kg/hr or less than and uric acid clearance is below 7.3 mL/min/1.73 m2. When classifying such cases as the normal type, there were 1,684 cases (74.1%) of the uric acid underexcretion type, 309 cases (13.6%) of the renal overload type, 224 cases (9.9%) of the mixed type, and 55 cases (2.4%) of the normal type. Compared with the frequency of the type classification of hyperuricemia described in the guidelines established about 40 years ago, these results showed a 14.1% higher rate for the uric acid underexcretion type and a 15.1% lower rate for the mixed type. According to a survey by the Ministry of Health, Labour and Welfare, Japanese men's weight had increased by about 10 kg in 2019 compared with 1975. It is considered that due to the increased body weight, the amount of urinary uric acid excreted per unit weight, which is an indicator of uric acid production, was calculated to be low, and the factors contributing to uric acid production decreased, resulting in an increase in the frequency of the uric acid underexcretion type. In the future, it will be necessary to revise the type classification criteria for hyperuricemia to take into account the current physique of Japanese people.
