Quantitative urinalysis. Diagnosing urinary tract infection in men

Area of Science:

• Clinical diagnostics
• Microbiology

Background:

• Urinary tract infections (UTIs) are common, necessitating accurate diagnostic methods.
• Traditional urinalysis involves centrifugation and resuspension, which can be time-consuming and introduce variability.
• Quantitative urinalysis offers a potentially more direct and reliable approach.

Purpose of the Study:

• To evaluate the efficacy of counting white blood cells (WBCs) in uncentrifuged urine for diagnosing UTIs.
• To establish reference ranges for WBC counts in infected and uninfected urine specimens.
• To compare this method with traditional urinalysis techniques.

Main Methods:

• White blood cell counts were performed using a hemocytometer on uncentrifuged urine samples.
• Urine specimens were collected from both infected and uninfected patients, including those with indwelling catheters.
• WBC counts were correlated with the presence or absence of urinary tract infection.

Main Results:

• Uninfected urine typically showed ≤10^3 WBCs/mL (range up to 8x10^3/mL).
• Infected urine consistently demonstrated >10^4 WBCs/mL, with a mean of 3.1x10^5 WBCs/mL.
• A clear distinction in WBC counts was observed between infected and uninfected urine, with minimal overlap.
• Similar findings were noted in patients with indwelling catheters, suggesting infection rather than colonization.

Conclusions:

• Quantitative urinalysis of uncentrifuged urine is a valid and easily obtainable method for diagnosing UTIs.
• The absence of pyuria (high WBC count) strongly indicates the absence of a UTI.
• This hemocytometer-based method should supersede traditional urine sediment analysis for WBC counting in UTI diagnostics.