Hoogenberg K, Visser P, Marrink J, Sluiter W J, Dullaart R P
Department of Internal Medicine, Groningen State University Hospital, The Netherlands.
Diabet Med. 1996 Jul;13(7):651-5. doi: 10.1002/(SICI)1096-9136(199607)13:7<651::AID-DIA140>3.0.CO;2-M.
The previous observation that urinary IgG excretion is increased in normoalbuminuric insulin-dependent (IDDM) patients is unexplained and could possibly be related to a laboratory phenomenon. When untreated urine samples were stored -20 degrees C for 2 to 4 weeks, the IgG/albumin Index (IgG clearance divided by albumin clearance) was higher in normoalbuminuric IDDM patients than in control subjects (0.91 (0.68-1.54), n = 27 vs 0.72 (0.55-0.79), n = 15 (median (interquartile range)), p < 0.05). In normo- and microalbuminuric IDDM patients the IgG/albumin index was higher in urine samples with glucose than without glucose (1.16 (0.93-1.68), n = 11 vs 0.73 (0.50-0.91), n = 16, p < 0.05, and 0.33 (0.23-0.60), n = 17 vs 0.15 (0.10-0.26), n = 14, p < 0.02 for normo- and microalbuminuric patients, respectively). We, therefore, evaluated the preserving effects of glucose and bovine serum albumin (BSA) on urinary IgG after 1 h to 16 weeks of freezing at -20 degrees C in 4 non-diabetic subjects (proteinuria ranging from 0.05 to 8.0 g 24 h-1). Urine samples were either stored without precautions or treated with addition of phosphate buffer, BSA (1%) and glucose 100 and 300 mM). The weekly decline from 1 to 16 weeks of IgG in the urine aliquots diluted 1:1 with buffered glucose 300 mM and glucose 300 mM + BSA 1% was insignificant, whereas urinary IgG declined with all other storage regimes (p < 0.05). These results suggest that glucose in urinary specimens of IDDM patients prevents at least in part the loss of urinary IgG and may thus explain the higher urinary IgG/albumin index when unprocessed urine is stored frozen before assay. Laboratory precautions are necessary when urinary IgG cannot be measured immediately.
以往观察到，正常白蛋白尿的胰岛素依赖型（IDDM）患者尿IgG排泄增加，其原因不明，可能与实验室现象有关。当未处理的尿液样本在-20℃储存2至4周时，正常白蛋白尿的IDDM患者的IgG/白蛋白指数（IgG清除率除以白蛋白清除率）高于对照组（0.91（0.68 - 1.54），n = 27，对照组为0.72（0.55 - 0.79），n = 15（中位数（四分位间距）），p < 0.05）。在正常白蛋白尿和微量白蛋白尿的IDDM患者中，有葡萄糖的尿液样本的IgG/白蛋白指数高于无葡萄糖的样本（正常白蛋白尿患者：1.16（0.93 - 1.68），n = 11，无葡萄糖样本为0.73（0.50 - 0.91），n = 16，p < 0.05；微量白蛋白尿患者：0.33（0.23 - 0.60），n = 17，无葡萄糖样本为0.15（0.10 - 0.26），n = 14，p < 0.02）。因此，我们评估了在4名非糖尿病受试者（蛋白尿范围为0.05至8.0 g/24 h-1）中，在-20℃冷冻1小时至16周后，葡萄糖和牛血清白蛋白（BSA）对尿IgG的保存作用。尿液样本要么无防护措施储存，要么添加磷酸盐缓冲液、1% BSA和100及300 mM葡萄糖处理。用300 mM缓冲葡萄糖和300 mM葡萄糖 + 1% BSA 1:1稀释的尿液等分试样中，IgG从1周至16周的每周下降不显著，而其他所有储存方式下尿IgG均下降（p < 0.05）。这些结果表明，IDDM患者尿液标本中的葡萄糖至少部分防止了尿IgG的损失，这可能解释了在检测前未处理的尿液冷冻储存时尿IgG/白蛋白指数较高 的现象。当不能立即检测尿IgG时，实验室防护措施是必要的。
