What is the significance of 3 squamous epithelial cells in a urinalysis for a menstruating female patient with leukocytosis, leukocyte esterase, bacteriuria, hematuria, proteinuria, and ketonuria?

Significance of 3 Squamous Epithelial Cells in Urinalysis

The finding of 3 squamous epithelial cells per low-power field in this menstruating female patient with multiple urinalysis abnormalities (leukocytosis, leukocyte esterase, bacteriuria, hematuria, proteinuria, ketonuria) indicates likely specimen contamination from vaginal/perineal sources, but does NOT rule out a true urinary tract infection given the constellation of other findings and clinical context.

Understanding Squamous Epithelial Cells

• Squamous epithelial cells (SECs) originate from the distal urethra, vaginal mucosa, or perineal skin, not from the bladder or upper urinary tract 1
• The presence of SECs is a poor predictor of urine culture contamination, with only 21% of midstream clean-catch samples with SECs showing actual bacterial contamination in women 1
• SECs were present in 94% of catheterized samples from women with zero bacterial contamination, demonstrating that SECs alone do not indicate contamination 1
• However, specimens with ≥10 SECs/mm³ had significantly more mixed growth (53% vs 22%) compared to specimens with <10 SECs/mm³ 2

Impact on Urinalysis Interpretation

• The presence of SECs may reduce the predictive performance of traditional urinalysis measures for bacteriuria 3
• Urinalysis samples with <8 SECs/lpf predicted bacteriuria better (sensitivity 75%, specificity 84%) than samples with >8 SECs/lpf (sensitivity 86%, specificity 70%) 3
• The positive likelihood ratio for predicting bacteriuria drops from 4.98 in the absence of SECs to 2.35 when >8 SECs/lpf are present 3

Clinical Decision Algorithm for This Patient

Step 1: Assess for Specific UTI Symptoms

• Look specifically for dysuria, frequency, urgency, fever >38°C, suprapubic pain, or new/worsening urinary incontinence 4
• Do not attribute non-specific symptoms like confusion or functional decline to UTI without specific urinary symptoms 4
• If the patient lacks specific urinary symptoms, do not pursue further UTI testing or treatment 4

Step 2: Consider Menstruation as a Confounding Factor

• Menstruation is a recognized benign cause that should prompt repeat evaluation after the cause is excluded 5
• Hematuria during menstruation requires microscopic confirmation after menstruation resolves before initiating referral 5
• The American College of Physicians recommends up to 3 repeated analyses when menstruation, viral illness, or vigorous exercise is suspected 5

Step 3: Evaluate the Quality of Other Urinalysis Findings

• The combination of positive leukocyte esterase with bacteriuria increases diagnostic accuracy substantially for UTI 4
• Leukocyte esterase has moderate sensitivity (83%) but limited specificity (78%), improving to 93% sensitivity when combined with nitrite testing 4
• The presence of proteinuria and ketonuria may indicate systemic illness or dehydration rather than isolated UTI 4

Step 4: Obtain Proper Specimen Collection

• If strong clinical suspicion for UTI exists despite potential contamination, obtain a properly collected specimen before making treatment decisions 4
• For women unable to provide clean specimens, in-and-out catheterization is recommended to avoid contamination 4
• Process specimens within 1 hour at room temperature or 4 hours if refrigerated 4

Step 5: Culture Decision

• If symptomatic with pyuria (≥10 WBCs/HPF or positive leukocyte esterase) AND acute onset of UTI-associated symptoms, obtain urine culture before starting antibiotics 4
• Collect culture before initiating antimicrobial therapy to guide definitive therapy 4
• Do not delay culture collection—always obtain culture before antibiotics in cases with significant pyuria 4

Critical Pitfalls to Avoid

• Do not dismiss the entire urinalysis as contaminated based solely on the presence of 3 SECs, as this is a low count and SECs are poor predictors of contamination 1, 3
• Do not treat based on urinalysis alone without confirming specific urinary symptoms 4
• Do not assume all positive cultures represent infection—distinguish true UTI from asymptomatic bacteriuria, which has 10-50% prevalence in certain populations 4
• Women have substantially lower rates of urology referral (8-28% vs 36-47% in men) and longer delays to evaluation despite presenting with more advanced disease, representing a critical disparity that should be avoided 5

Special Consideration for Hematuria

• A threshold of at least 3 erythrocytes per HPF is considered abnormal and warrants evaluation 5
• If menstruation is suspected as the cause of hematuria, repeat the evaluation after menstruation to document resolution 5
• Women with hematuria typically present with more advanced bladder cancer and have higher case-fatality rates than men, making timely evaluation critical 5