High Prevalence of Sterile Pyuria in the Setting of Sexually Transmitted Infection in Women Presenting to an Emergency Department

INTRODUCTION: The clinical presentations for sexually transmitted infections (STI) and urinary tract infections (UTI) often overlap, and symptoms of dysuria and urinary frequency/urgency occur with both STIs and UTIs. Abnormal urinalysis (UA) findings and pyuria are common in both UTIs and STIs, and confirmatory urine cultures are not available to emergency clinicians to aid in decision-making regarding prescribing antibiotics for UTIs. The objective of this study was to determine the frequency of sterile pyuria in women with confirmed STIs, as well as whether the absolute number of leukocytes on microscopy or nitrite on urine dipstick correlated with positive urine cultures in patients with confirmed STIs. We also sought to determine how many patients with STIs were inappropriately prescribed a UTI antibiotic. METHODS: We performed a retrospective chart review of patients aged 18–50 who had a urinalysis and pelvic examination in the emergency department (including cervical cultures), and tested positive for Neisseria gonorrhoeae, Chlamydia trachomatis, and/or Trichomonas vaginalis. Descriptive statistics were obtained for all variables, and associations between various findings were sought using the Fisher’s exact test for categorical variables. We calculated comparison of proportions using the N-1 chi-squared analysis. RESULTS: A total of 1,052 female patients tested positive for Neisseria gonorrhoeae, Chlamydia trachomatis, and/or Trichomonas vaginalis and were entered into the database. The prevalence of pyuria in all cases was 394/1,052, 37% (95% confidence interval [CI] [0.34–0.40]). Of the cases with pyuria, 293/394, 74% (95% CI [0.70–0.78]) had sterile pyuria with negative urine cultures. The prevalence of positive urine cultures in our study population was 101/1,052, 9.6% (95% CI [0.08–0.11]). Culture positive urines had a mean of 34 leukocytes per high-power field, and culture negative urines had a mean of 24 leukocytes per high-power field, with a difference of 10, (95% CI [3.46–16.15]), which was statistically significant (p=0.003). Only 123 cases tested positive for nitrite on the urinalysis dipstick; 50/123, 41% (95% CI [0.32–0.49]) had positive urine cultures, and 73/123, 59% (95% CI [0.51–0.68]) had negative urine cultures. Nitrite-positive urines were actually 18% more likely to be associated with negative urine cultures in the setting of positive STI cases, (95% CI [4.95–30.42], p=0.0048). Antibiotics were prescribed for 295 patients with suspected UTI. Of these, 195/295, 66% (95% CI [0.61–0.71]) had negative urine cultures, and 100/295, 34% (0.33, 95% CI [0.28–0.39]) had positive urine cultures. Chi-square analysis yielded a difference of these proportions of 32% (95% CI [23.92–39.62], p<0.0001). CONCLUSION: This study demonstrated that in female patients with STIs who have pyuria, there is a high prevalence of sterile pyuria. Our results suggest that reliance on pyuria or positive nitrite for the decision to add antimicrobial therapy empirically for a presumed urinary tract infection in cases in which an STI is confirmed or highly suspected is likely to result in substantial over-treatment.