Dataset for: Reference Values of Renal Tubular Function Tests Are Dependent On Age And Kidney Function

Background: Electrolyte disorders due to tubular disorders are rare, and knowledge about validated clinical diagnostic tools such as tubular function tests is sparse. Reference values for tubular function tests are based on studies with small sample size in young healthy volunteers. Patients with tubular disorders however frequently are older and can have a compromised renal function. We therefore evaluated four tubular function tests in individuals with different ages and renal function. Methods: We performed furosemide, thiazide, furosemide-fludrocortisone and desmopressin tests in healthy individuals aged 18 to 50 years, healthy individuals aged more than 50 years and individuals with compromised renal function. For each tubular function test we included 10 individuals per group. Results: The responses in young healthy individuals were in line with previously reported values in literature. The maximal increase in fractional chloride excretion after furosemide was below the lower limit of young healthy individuals in 5/10 older subjects and in 2/10 patients with compromised renal function. The maximal increase in fractional chloride excretion after thiazide was below the lower limit of young healthy individuals in 6/10 older subjects and in 7/10 patients with compromised renal function. Median maximal urine osmolality after desmopressin was 1002 mosmol/kg H2O in young healthy individuals, 820 mosmol/kg H2O in older subjects and 624 mosmol/kg H2O in patients with compromised renal function. Conclusions: Reference values for tubular function tests obtained in young healthy adults cannot simply be extrapolated to older patients or patients with compromised kidney function. Larger validation studies are needed to define true reference values in these patient categories.

背景：由肾小管疾病（tubular disorders）引发的电解质紊乱较为罕见，且针对肾小管功能试验（tubular function test）这类经过验证的临床诊断工具的相关认知仍较为匮乏。目前，肾小管功能试验的参考值均基于针对年轻健康志愿者的小样本研究。然而，肾小管疾病患者往往年龄偏大，且可能存在肾功能受损的情况。为此，本研究针对不同年龄、不同肾功能状态的人群，对四项肾小管功能试验进行了评估。
方法：本研究纳入18~50岁健康志愿者、50岁以上健康人群以及肾功能受损患者，分别开展呋塞米（furosemide）、噻嗪类（thiazide）、呋塞米-氟氢可的松（furosemide-fludrocortisone）及去氨加压素（desmopressin）试验；每项肾小管功能试验每组纳入10名受试者。
结果：年轻健康志愿者的试验响应结果与既往文献报道的参考值相符。呋塞米试验后，氯化物排泄分数（fractional chloride excretion）的最大增幅，在10名老年受试者中有5名低于年轻健康志愿者的下限值，在10名肾功能受损患者中有2名低于该下限值。噻嗪类试验后，氯化物排泄分数的最大增幅，在10名老年受试者中有6名低于年轻健康志愿者的下限值，在10名肾功能受损患者中有7名低于该下限值。去氨加压素试验后，年轻健康志愿者的最大尿渗透压（urine osmolality）中位数为1002 mosmol/kg H₂O，老年受试者为820 mosmol/kg H₂O，肾功能受损患者为624 mosmol/kg H₂O。
结论：基于年轻健康成年人得到的肾小管功能试验参考值，无法直接外推至老年患者或肾功能受损患者；需开展更大样本量的验证研究，以明确上述人群的真实参考值。