Microscopic or occult hematuria, when reflex testing is not good laboratory practice

Area of Science:

• Clinical Chemistry
• Urology
• Laboratory Medicine

Background:

• Current practice for diagnosing hematuria involves dipstick urinalysis followed by microscopic examination if positive.
• Discordant results often trigger reflex testing for urinary myoglobin and hemoglobin, a practice lacking strong evidence.
• Existing recommendations for red blood cell (RBC) counts in microscopic hematuria diagnosis are not evidence-based.

Purpose of the Study:

• To evaluate the evidence base for current diagnostic practices in hematuria detection.
• To propose revised reference ranges for RBCs in dipstick urinalysis based on flow cytometry data.
• To assess the utility and recommend against unnecessary reflex testing for myoglobin and hemoglobin.

Main Methods:

• Review of current literature and expert recommendations for hematuria diagnosis.
• Comparison of dipstick and microscopic urinalysis findings with flow cytometry data.
• Analysis of the sensitivity, precision, and accuracy of reflex testing methods.

Main Results:

• Current recommendations for hematuria diagnosis are not evidence-based.
• Proposed new reference ranges for RBCs on reagent strips: 25x10^6 cells/L for young men and 50x10^6 cells/L for other adults.
• Reflex testing for myoglobin and hemoglobin shows inferior performance compared to established methods.

Conclusions:

• The standard approach to hematuria diagnosis requires revision.
• Increased RBC thresholds on reagent strips are proposed, aligning with flow cytometry.
• Unnecessary reflex testing for myoglobin and hemoglobin should be discontinued to improve laboratory efficiency and accuracy.