A Study on the Standardization of Sample Preparation for Urine Sediment Microscopic Examination

Abstract

Urinalysis is a fundamental diagnostic test routinely performed in clinical laboratories. We evaluated two manual microscopy methods, including a novel protocol, against the standardized chamber method. A total of 402 specimens, comprising 201 positive each for red blood cells (RBCs) and white blood cells (WBCs) by the strip test and automated urine sediment analyzer, were selected for the analysis. The correlation coefficients between the standardized chamber method and the novel protocol RBC and WBC test were both r=0.98, indicating a high degree of correlation. The pair-wise agreement rates for the same grade between these two methods were 86.1% for RBCs and 88.6% for WBCs, with rates within one grade difference of both at 99.5%. In contrast, the agreement rates between the standardized chamber method and smaller or medium-sized laboratory methods were notably lower, with the same-grade rates at 11.9% for RBCs and 13.4% for WBCs, and within one grade difference at 67.2% and 74.1%, respectively. Additional analyses using the intraclass correlation coefficient and Bland-Altman plots confirmed that the novel protocol exhibited superior agreement compared to the other three manual microscopy methods tested. Therefore, we recommend the novel protocol as a standardized procedure for urine sediment preparation, given its high correlation and agreement with the standardized chamber method.

Keywords

• microscopy
• standardization
• urinalysis