Urine formed particles analysis is an important mean for evaluating kidney function, mainly including red blood cells, white blood cells, casts, pathological casts, epithelial cells, crystals and pathogens. Certain specific pathological conditions feature more complex and volatile urine samples, which brings difficulties to the diagnosis, identification and prognosis. Furthermore, interferences such as mucus often leads to confusion with casts and increasing risk of misdiagnosis. 

Challenges in Differentiating Cast from Mucus-Positive Samples

Mucus exist in normal urine samples, especially in female's urine sample. In addition, inflammation and stimulation in human body also generates large quantities of mucus. Clinical studies have shown that mucus and epithelial cells can affect the identification of casts, so correctly identifying them is crucial to making reasonable diagnosis and treatment. Up to now, manual microscopy is still the gold standard for urine formed particles analysis. However, at a large number of urine specimens, manual microscopy is not only inefficient, but also easily affected by operating procedures and subjective factors, resulting in errors, and it is difficult to meet the detection needs of large quantities of samples. Although some fully automated urine analysis systems can improve efficiency, the sensitivity and specificity of cast detection in most devices are significantly reduced under the interference of mucus.

Technological Innovation Breaks Through the Limits of Traditional Detection

In an evaluation study which enrolled 1,000 samples from a tertiary hospital in China, 320 mucus-positive samples are analyzed to detect cast with three different urine analyzers and manual microscopy in order to further explore the impact of mucus on cast analysis. With manual microscopy as the standard, performances of U3600 and two other urine sediment analyzers in detecting casts in mucus-positive samples were evaluated. From the results in Table 1, it can be seen that under the interference of mucus, compared with the other two devices, U3600 features the highest agreement with microscopy, and the sensitivity and specificity as well as the positive predictive value for cast samples are all high, showing good detection performance. The U3600 automated urinalysis system has optimized the algorithm, and the image segmentation and recognition are more accurate. In the mucus-positive samples, the detection of cast shows 83% consistency with the "gold standard" manual microscopy. This technology has greatly facilitated clinical differentiation between cast and mucus, and reduced the misdiagnosis rate and missed diagnosis rate of related diseases in high mucus cases.

Zybio U3600 automated urinalysis system adopts laminar flow imaging technology to detect formed particles. Based on the advanced technology, the loaded sample enters the thin layer structure of the flow cell under the wrapping of the sheath fluid for urine analysis. Wrapped by the sheath fluid, the sample flows through the thin layer structure of the flow cell at the thickness of a single layer of cells, and then is captured by high-speed camera. This flow technology not only leave out sample centrifugation and staining, improving efficiency, but also can capture real particles images at a constant speed, efficiently and accurately, so that the results can be traced and easy to re-examine. It can meet the needs of clinical urinalysis and provide more reliable and accurate assistance for clinical diagnosis and treatment.