Discrediting microscopic pyuria and leucocyte esterase as diagnostic surrogates for infection in patients with lower urinary tract symptoms: results from a clinical and laboratory evaluation

• Published in: BJU international 2013-07, Vol.112 (2), p.231-238
• Main Authors: Kupelian, Anthony S., Horsley, Harry, Khasriya, Rajvinder, Amussah, Rasheedah T., Badiani, Raj, Courtney, Angela M., Chandhyoke, Nihil S., Riaz, Usama, Savlani, Karishma, Moledina, Malik, Montes, Samantha, O'Connor, Dominic, Visavadia, Rakhee, Kelsey, Michael, Rohn, Jennifer L., Malone‐Lee, James
• Format: Article
• Language: English
• Subjects: Adult; Bacterial diseases; Bacterial diseases of the urinary system; Biological and medical sciences; Biomarkers; Carboxylic Ester Hydrolases - urine; Clinical Laboratory Techniques; Confidence intervals; Female; Human bacterial diseases; Humans; Infections; Infectious diseases; lower urinary tract symptoms; Lower Urinary Tract Symptoms - complications; Lower Urinary Tract Symptoms - diagnosis; Lower Urinary Tract Symptoms - microbiology; Lower Urinary Tract Symptoms - urine; Male; Medical sciences; Medical treatment; microscopic pyuria; Middle Aged; Nephrology. Urinary tract diseases; Prospective Studies; Pyuria - etiology; Urinary system involvement in other diseases. Miscellaneous; urinary tract infection; Urinary Tract Infections - complications; Urinary Tract Infections - diagnosis; Urinary Tract Infections - urine; Urinary tract. Prostate gland; Urogenital system; Women
• ISSN: 1464-4096; 1464-410X
• DOI: 10.1111/j.1464-410X.2012.11694.x

What's known on the subject? and What does the study add? Microscopic pyuria is widely used as a surrogate marker of infection, although there is little data supporting its use in patients who present with non‐acute LUTS. The effects of urinary storage, preservation, and the use of laboratory methods to enhance leucocyte detection, are also unclear. This large, prospective study highlights the poor performance of dipstick urine analysis, and direct microscopy, as surrogate markers of UTI in patients with LUTS. A series of laboratory analyses also examine the effects of urine handling and processing on test integrity, which have important implications for clinical practice. Objective To evaluate the diagnostic performance of pyuria as a surrogate marker of urinary tract infection (UTI) in patients with chronic lower urinary tract symptoms (LUTS), and determine the impact of sample storage, cytocentrifugation, and staining techniques, on test performance. Patients and Methods Between 2008 and 2011, we recruited 1223 patients (120 men; 1103 women; mean age 54 years) with one or more LUTS from a specialist urological outpatient service. We conducted a prospective observational study to determine the performance of microscopic pyuria ≥10 wbc/μL as a surrogate marker of UTI in patients with LUTS. All patients provided clean‐catch midstream urine (MSU) samples for analysis, and routine microbiological cultures were used as our reference standard. We also scrutinised the performance of dipstick leucocyte esterase ≥ ‘trace’ in the detection of microscopic pyuria. The influence of sample handling and processing on test performance was examined in a series of laboratory studies. The effects of storage on leucocyte decay were determined using repeated microscopic assessments of individual urine samples, to plot temporal changes in leucocyte numbers. This study used varied storage conditions (≈20 °C and 4 °C), and boric acid preservation. Paired microscopic assessments were used to determine the effects of centrifugation on leucocyte salvage in spun/unspun samples (relative centrifugal force range 39–157 g). Similar methods were used to assess microscopic leucocyte quantification in stained/unstained urine (Sternheimer‐Malbin protocol). Results The positive predictive value (PPV) and negative predictive value (NPV) of pyuria as a surrogate marker of UTI were 0.40 (95% confidence interval [CI] 0.37–0.43) and 0.75 (95% CI 0.73–0.76), respectively. The dipstick was unable