Jillings Ekp, Squires R A, Azarpeykan S, Lopez-Villalobos N
a School of Veterinary Science , Massey University , Private Bag 11-222, Palmerston North , 4442 , New Zealand.
b College of Public Health, Medical and Veterinary Sciences , James Cook University , 1 Solander Drive, Townsville , Queensland 4811 , Australia.
N Z Vet J. 2019 Mar;67(2):74-78. doi: 10.1080/00480169.2018.1556129. Epub 2019 Jan 15.
To determine the effect of contamination of urine with 0-5% blood, varying in haematocrit and protein concentrations, on the urine protein to creatinine ratio (UPC) in dogs, and to determine whether the colour of urine can be used to aid interpretation of UPC results.
Urine samples were collected by free catch from 18 dogs, all of which had UPC <0.2. Venous blood samples were also collected from each dog, and the blood from each dog was added to its own urine to produce serial concentrations of 0.125-5% blood. The colour of each urine sample was recorded by two observers scoring them as either yellow, peach, orange, orange/red or red. Protein and creatinine concentrations were determined, and dipstick analysis and sediment examination was carried out on each sample. Based on colour and dipstick analysis, samples were categorised as either having microscopic, macroscopic or gross haematuria. A linear mixed model was used to examine the effect of blood contamination on UPC.
The uncontaminated urine of all 18 dogs had a UPC <0.2. Adding blood to the urine samples resulted in an increase in UPC at all contamination concentrations compared to the non-contaminated urine (p<0.001). None of the 54 samples with microscopic haematuria had UPC >0.5. For 108 samples with macroscopic haematuria the UPC was >0.5 in 21 samples (19.4 (95% CI=13.1-27.9)%), and for 54 samples with gross haematuria 39 (72 (CI=59.1-82.4)%) had a UPC >0.5. No samples had a UPC >2.0 unless the blood contamination was 5% and only 3/18 (17%) samples at this blood contamination concentration had a UPC >2.0.
This study showed that while blood contamination of ≥0.125% does increase the UPC, if the urine remains yellow (microscopic haematuria), then there is negligible chance that a UPC >0.5 will be solely due to the added blood. In that scenario, attributing the proteinuria present to the haematuria in the sample would be inappropriate. However blood contamination that results in discolouration of the urine sample from yellow (indicating macroscopic or gross haematuria) could increase the UPC above the abnormal range and would need to be considered as a differential for the proteinuria. Thus knowledge of urine colour, even if limited to simple colour scores (yellow, discoloured, red) could be utilised to aid interpretation of the UPC in samples with haematuria.
确定血细胞比容和蛋白质浓度不同的0 - 5%血液污染犬尿液对尿蛋白肌酐比值（UPC）的影响，并确定尿液颜色是否可用于辅助解释UPC结果。
通过自由采集的方式从18只犬收集尿液样本，所有犬的UPC均<0.2。同时从每只犬采集静脉血样本，并将每只犬的血液加入其自身尿液中，制成0.125 - 5%血液的系列浓度样本。由两名观察者将每个尿液样本的颜色记录为黄色、桃色、橙色、橙红色或红色。测定蛋白质和肌酐浓度，并对每个样本进行试纸条分析和沉渣检查。根据颜色和试纸条分析，将样本分类为镜下血尿、肉眼血尿或重度血尿。使用线性混合模型研究血液污染对UPC的影响。
18只犬的未污染尿液UPC均<0.2。与未污染尿液相比，在所有污染浓度下向尿液样本中添加血液均导致UPC升高（p<0.001）。54例镜下血尿样本中无一例UPC>0.5。108例肉眼血尿样本中，21例（19.4（95%CI = 13.1 - 27.9）%）的UPC>0.5；54例重度血尿样本中，39例（72（CI = 59.1 - 82.4）%）的UPC>0.5。除非血液污染为5%，否则没有样本的UPC>2.0，且在此血液污染浓度下只有3/18（17%）的样本UPC>2.0。
本研究表明，虽然≥0.125%的血液污染确实会增加UPC，但如果尿液仍为黄色（镜下血尿），那么UPC>0.5仅由添加的血液导致的可能性微乎其微。在这种情况下，将样本中存在的蛋白尿归因于血尿是不合适的。然而，导致尿液样本从黄色变色（表明肉眼血尿或重度血尿）的血液污染可能会使UPC升高至异常范围以上，需要将其视为蛋白尿的鉴别诊断因素。因此，即使仅了解尿液颜色（如简单的颜色评分：黄色、变色、红色），也可用于辅助解释血尿样本中的UPC。
