血中茶鹼及咖啡因甲基尿酸代謝物之分析及其與尿酸值評估之影響

本研究旨在分析高尿酸血症病人血清中之尿酸濃度，藉以探討高尿酸血症病人在醫院所測之尿酸值偏高 (尿酸值>7mg/dl)，卻沒有痛風的症狀及急性發作現象的可能原因。本實驗于中部中山醫學院附設醫院內科門診部就診乏病人做為研究之母群，樣本取得分成尿酸值正常、高尿酸血症無痛風發作及醫師診斷為痛風病人等三組，並透過該院檢驗室收集血清，做常規尿酸t法分析以得知臨床分析之尿酸值，再以高效液相色層分析(High performance liquid chromatography;HPLC)血清中之尿酸、1,3-二甲基尿酸(茶鹼代謝物)及1,3,7-三甲基尿酸(咖啡因代謝物)等之含量，並以SAS軟體進行統計分析。結果以HPLC分析所得之尿酸值均低於尿酸t法所分析之值；而兩者之差距與1,3-甲二基尿酸及1,3,7-三甲基尿酸同時存在時成正相關(P<0.05)，與任何一者單獨存在時有些微差異，但無統計上之意義。此結果顯示，受檢病人血中若含有甲基尿酸衍生物 (來自於茶鹼及咖啡因的代謝)，將影響病人及尿酸t法檢查之尿酸檢測值偏高，是否因此形成臨床分析的假陽性，有待進一步的研究。
To investigate the causes that lead to high serum levels of uric acid >7 mg/dl) in patients free of gout-associated symptoms, both uricase assay and high performance liquid chromatography (HPLC) were conducted in sera prepared from patients with hyperuricemia or gout. Our results demonstrate that the levels of uric acid measured from HPLC are always lower than those obtained from uricase assays, and the differences seem to be positively related to the existence of uric acid derivatives: the 1,3-dimethyluric acid (DMUA) and the 1,3,7-trimethyluric acid (TMUA) (P<0.05). This suggests that high levels of methyl uric acids derived from theophylline and caffeine will cause the increased uric acid levels measured by uricase assay. Whether this leads to positive artifact clinically (such as hyperuricemia) needs further investigation.