Determination of appropriate urine volume cutoff values for voided urine specimens to assess adequacy

Incorporating urine volume into adequacy assessment was recommended by The Paris System for Reporting Urinary Cytology. The concept was relatively new, however, and supportive studies were sparse. We accordingly aimed to determine the role of urine volume in adequacy assessment and cutoff values for urine samples using ThinPrep (Hologic, Inc, MA) processing.

Archived consecutive urine cytology cases (n = 2117) were analyzed. Patient age, sex, collection method, urine volume and fixative (CytoLyt, Hologic, Inc) added, adequacy and diagnoses were documented. Adequate samples were defined as samples with >50 well-preserved, well-visualized urothelial cells. Diagnoses of suspicious and positive for high-grade urothelial carcinoma were combined for analysis. Statistical analysis was performed using IBM SPSS Statistics for Windows.

There was a correlation between urine volume and the unsatisfactory/less than optimal cellularity versus satisfactory samples (P ≤ 0.001) in voided urine specimens. A minimum of 10 mL of fresh voided urine was found to be a reasonable cutoff to achieve sufficient cellularity. Cutoff values of 30 mL for voided urine for the high-risk diagnosis were associated with the highest χ² statistic, although this was not statistically significant.

Urine volume was justified as an adequacy criterion in voided urine. Although 10 mL of fresh voided urine might achieve sufficient cellularity, higher volume (≥30 mL) is recommended in order to maximize the chance of detecting a high-risk diagnosis. Nevertheless, the presence of high-grade urothelial carcinoma can still be detected in low-volume (<20 mL) specimens. Hence, correlation of clinical information with voided urine volume cutoff values for individual cases might also be beneficial.