Defining Properly Collected Urine: Thresholds to Improve the Accuracy of Urinalysis for Microscopic Hematuria Evaluation in Women

Purpose: Microscopic hematuria is one of the most common office consults for urologists. While revised guidelines have risk-stratified patients to reduce unnecessary screening, they do not provide guidance concerning specimen quality. We sought to define "properly collected" specimens using catheterized urine samples as a reference to improve the utility of hematuria screening in women.

Materials and methods: We prospectively acquired same-visit voided and catheterized urine samples from 46 women referred for microscopic hematuria from September 2016 to March 2020. Characteristics of pre-referral urinalysis were compared to the matched specimens. True microscopic hematuria was defined as ≥3 red blood cells per high power field on catheterization.

Results: Catheterized urinalyses had significantly fewer red blood and squamous epithelial cells in comparison to both referral urinalyses (p=0.006, p=0.001, respectively) and same-day void urinalyses (p=0.02, p=0.04, respectively). As no catheterized sample had >2 squamous epithelial cells, we applied this squamous epithelial cell threshold to referral urinalyses for analysis. Addition of this criterion for "properly collected specimen" increased the positive predictive value of referral urinalyses from 46.1% to 68.8% for true microscopic hematuria. Fewer than 2 squamous epithelial cells with elevated RBC was a significant predictor for true microscopic hematuria (p=0.003).

Conclusions: Voided specimens in the urology clinic had significantly lower red blood cells than referral samples, indicating improved collection technique may reduce false positive urinalyses. Matched collection suggested that repeat collection by catheterization in women who present with >2 squamous epithelial cells per high power field on referral urinalysis may prevent unnecessary future work-up.