Meares-Stamey 4-Glass Test Procedure for Chronic Bacterial Prostatitis
The Meares-Stamey 4-glass test involves sequential collection of four specimens: first-void urine (VB1), midstream urine (VB2), expressed prostatic secretions (EPS) via prostatic massage, and post-massage urine (VB3), with a positive result defined as a 10-fold higher bacterial count in the EPS compared to midstream urine. 1, 2
Step-by-Step Collection Protocol
Specimen Collection Sequence
VB1 (First-void urine): Collect the initial 5-10 mL of voided urine to sample the urethra 3, 4
VB2 (Midstream urine): Collect midstream urine (approximately 10-20 mL) to sample the bladder 1, 3
EPS (Expressed prostatic secretions): Perform digital rectal examination with prostatic massage to express prostatic fluid, collecting any secretions that appear at the urethral meatus 1, 3
VB3 (Post-massage urine): Immediately after prostatic massage, collect the first 5-10 mL of voided urine to capture prostatic secretions that drained into the urethra 1, 4
Laboratory Processing Requirements
Transport time: All specimens must reach the laboratory within 1 hour in closed sterile containers, or be refrigerated at 4°C if transport is delayed 1
Diagnostic procedures: Perform both Gram stain or cell counts to identify inflammatory cells, and aerobic culture to identify pathogens 1, 3
Quantitative culture: Bacterial colony counts must be quantified for each specimen to allow comparison 1, 5
Interpretation Criteria
A positive test requires a 10-fold (or greater) higher bacterial count in the EPS compared to the VB2 (midstream urine) specimen. 1, 2, 3
The most common pathogens are Gram-negative organisms including E. coli (approximately 50% of cases), followed by Enterococcus species (approximately 32%), Proteus mirabilis, Enterobacter species, and Serratia marcescens 3, 6
White blood cell counts should also be compared, with the optimal cutpoint being ≥3 WBCs in VB3 to predict ≥5 WBCs in EPS (76% sensitivity, 70% specificity) 4
Simplified 2-Glass Alternative
When EPS cannot be obtained (which occurs in >50% of attempts), the 2-glass test using only VB2 (midstream urine) and VB3 (post-massage urine) is an acceptable alternative with >96% concordance to the 4-glass test. 2, 3, 4
The 2-glass test has 44-54% sensitivity but 100% specificity for detecting uropathogens when compared to the full 4-glass test 4
VB3 white blood cell count ≥4 predicts ≥10 WBCs in EPS with 62% sensitivity and 75% specificity 4
Critical Contraindications and Pitfalls
Never perform prostatic massage in acute bacterial prostatitis due to high risk of bacteremia—this is a strong contraindication 2, 3
Failure to obtain EPS occurs in less than 50% of patients in routine practice, making the test non-diagnostic unless the 2-glass variant is used 7
The diagnostic yield improves significantly (from 31% to 64%) when performed by dedicated staff experienced in prostatitis evaluation rather than general urologists 6
Patient selection matters: the test has 81% positivity in patients with prostatitis symptoms only, versus only 29-34% in patients with mixed or BPH-only symptoms 6
Semen culture alone should not be used for diagnosis as it cannot differentiate prostatic infection from urethral or seminal vesicle contamination 2, 3