Diagnosis Cohort study
Voided midstream urine culture is a good test for acute cystitis in premenopausal women 10.1136/eb-2013-101693
Lindsey Cox, J Quentin Clemens Department of Urology, University of Michigan, Ann Arbor, Michigan, USA Correspondence to: Dr J Quentin Clemens, Department of Urology, University of Michigan, 1500 E. Medical Center Drive 3875 Taubman Center, SPC 5330, Ann Arbor, MI 48109-5330, USA; lmenchen@med. umich.edu
Commentary on: Hooton TM, Roberts PL, Cox ME, et al. Voided midstream urine culture and acute cystitis in premenopausal women. N Engl J Med 2013;369:1883–91.
Context Uncomplicated acute cystitis is a common and uncomfortable condition in premenopausal women. Controversy exists over the value of culture data obtained from clean-catch midstream urine specimens for directing antimicrobial therapy, due to the risk of contamination by periurethral and vaginal organisms affecting the detection of true bladder bacteriuria. In the past, bacterial colony counts have been used to determine the threshold for clinically meaningful results. The authors attempt to clarify this issue by comparing culture results in premenopausal women displaying symptoms of acute cystitis from specimens obtained through midstream urine collection with specimens obtained by urethral catheterisation.
Methods The study compared the results of 202 paired, quantitative cultures of midstream and catheterised urine specimens from premenopausal women with symptoms of acute cystitis (dysuria and urinary frequency or urgency) and no complicating factors, or signs or symptoms of upper tract infections. Each participant provided a clean-catch midstream urine culture and a subsequent catheter-obtained bladder culture. Results are reported as sensitivity, specificity, positive and negative predictive values of midstream urine culture (compared with catheterised bladder culture) based on the organism detected, and the correlation (r) of the relationship between bacterial colony counts for specific organisms in midstream and catheterised specimens.
midstream urine cultures were 93% for growth of at least 102 colony forming units (CFU)/mL and 99% for 104 CFU/mL. For enterococci and group B streptococci, PPV was low for all colony counts.
Commentary The study shows the reliability of voided midstream urine culture to detect E coli causing acute bacterial cystitis in premenopausal women, with a very high sensitivity and specificity of E coli alone or with other pathogens in the midstream culture—even at low colony counts. The authors suggest that false negatives may occur if laboratories do not report low colony counts of E coli in midstream urine cultures. In addition, it is significant that E coli remains the most common uropathogen causing acute cystitis in this population; the authors suggest that the rare presence of bladder bacteriuria corresponding with midstream cultures positive for group B streptococci and enterococci indicates that these organisms rarely cause cystitis. Treatment decisions for patients whose midstream urine culture demonstrates growth of non-E coli Gram-negative rods ( particularly at low colony counts), enterococci, group B streptococci and S saprophyticus and other Gram-positive organisms remain difficult. The smaller sample size of non-E coli-positive midstream cultures in this study makes generalising these results challenging. The results suggest that the next step in management of patients with a non-E coli midstream urine culture may be a repeat specimen obtained by catheterisation. Clinical guidelines indicate that symptom-based empiric antimicrobial treatment of premenopausal women, without obtaining a culture, is a reasonable first approach.1 2 Midstream urine cultures are noninvasive, easy to perform and could potentially enhance antibiotic stewardship. Nevertheless, the value these tests add to the treatment of patients at the initial presentation of symptoms is unclear. Clinical situations in which a urine culture is indicated include: patients with symptoms that recur within 2–4 weeks of a previous similar episode, especially with recent exposure to antimicrobial therapy; patients with unclear history or atypical symptoms; patients with any factors that would place them in a ‘complicated’ category (eg, signs or symptoms of upper tract infection, diabetes, anatomic or functional changes of the urinary tract). It is also important to keep in mind that the study’s results may not apply to acute cystitis in adolescent, pregnant or postmenopausal women. It is notable that a significant proportion of study participants (26%) did not have culture-proven bacterial cystitis, based on the catheterised urine sample. The authors attribute this to possible urethritis or noninfectious causes. As mentioned elsewhere, these results suggest that a substantial proportion of women presenting with symptoms of acute cystitis may ultimately be found to have another aetiology for the symptoms.3 This reinforces the standard recommendation to obtain a urine culture in all patients with acute cystitis symptoms who do not respond promptly to empiric antibiotic therapy. Competing interests None.
Findings The median age of participants was 22 years; 73% were white. At least one organism was cultured from 99% of midstream specimens and 74% of catheter specimens. Escherichia coli was found in 132 episodes (65%). In 120 of 131 episodes (92%), E coli grew in midstream and catheter cultures. Of 114 episodes in which E coli grew with any other organism in midstream samples, 104 (91%) showed E coli growth in catheter urine cultures. E coli colony counts in midstream urine and catheter urine were strongly correlated (r=0.944). Strong correlations (r=0.999) were also found for Klebsiella pneumonia (10 episodes) and Staphylococcus saprophyticus (6 episodes). Positive predictive values (PPV) for E coli in voided
References 1. Grabe M, Bjerklund-Johansen T, Botto H, et al. Uncomplicated UTIs in adults. In: Guidelines on urological infections. Arnhem: European Association of Urology, 2011:15–27. 2. Bent S, Nallamothu B, Simel D. Does this woman have an acute uncomplicated urinary tract infection? J Am Med Assoc 2002;287:2701–10. 3. Donnenberg MS. Uncomplicated cystitis–not so simple. N Engl J Med 2013;369:1959–60.
Evid Based Med August 2014 | volume 19 | number 4 |
151
Copyright of Evidence Based Medicine is the property of BMJ Publishing Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Voided midstream urine culture is a good test for acute cystitis in premenopausal women 10.1136/eb-2013-101693
Lindsey Cox, J Quentin Clemens Department of Urology, University of Michigan, Ann Arbor, Michigan, USA Correspondence to: Dr J Quentin Clemens, Department of Urology, University of Michigan, 1500 E. Medical Center Drive 3875 Taubman Center, SPC 5330, Ann Arbor, MI 48109-5330, USA; lmenchen@med. umich.edu
Commentary on: Hooton TM, Roberts PL, Cox ME, et al. Voided midstream urine culture and acute cystitis in premenopausal women. N Engl J Med 2013;369:1883–91.
Context Uncomplicated acute cystitis is a common and uncomfortable condition in premenopausal women. Controversy exists over the value of culture data obtained from clean-catch midstream urine specimens for directing antimicrobial therapy, due to the risk of contamination by periurethral and vaginal organisms affecting the detection of true bladder bacteriuria. In the past, bacterial colony counts have been used to determine the threshold for clinically meaningful results. The authors attempt to clarify this issue by comparing culture results in premenopausal women displaying symptoms of acute cystitis from specimens obtained through midstream urine collection with specimens obtained by urethral catheterisation.
Methods The study compared the results of 202 paired, quantitative cultures of midstream and catheterised urine specimens from premenopausal women with symptoms of acute cystitis (dysuria and urinary frequency or urgency) and no complicating factors, or signs or symptoms of upper tract infections. Each participant provided a clean-catch midstream urine culture and a subsequent catheter-obtained bladder culture. Results are reported as sensitivity, specificity, positive and negative predictive values of midstream urine culture (compared with catheterised bladder culture) based on the organism detected, and the correlation (r) of the relationship between bacterial colony counts for specific organisms in midstream and catheterised specimens.
midstream urine cultures were 93% for growth of at least 102 colony forming units (CFU)/mL and 99% for 104 CFU/mL. For enterococci and group B streptococci, PPV was low for all colony counts.
Commentary The study shows the reliability of voided midstream urine culture to detect E coli causing acute bacterial cystitis in premenopausal women, with a very high sensitivity and specificity of E coli alone or with other pathogens in the midstream culture—even at low colony counts. The authors suggest that false negatives may occur if laboratories do not report low colony counts of E coli in midstream urine cultures. In addition, it is significant that E coli remains the most common uropathogen causing acute cystitis in this population; the authors suggest that the rare presence of bladder bacteriuria corresponding with midstream cultures positive for group B streptococci and enterococci indicates that these organisms rarely cause cystitis. Treatment decisions for patients whose midstream urine culture demonstrates growth of non-E coli Gram-negative rods ( particularly at low colony counts), enterococci, group B streptococci and S saprophyticus and other Gram-positive organisms remain difficult. The smaller sample size of non-E coli-positive midstream cultures in this study makes generalising these results challenging. The results suggest that the next step in management of patients with a non-E coli midstream urine culture may be a repeat specimen obtained by catheterisation. Clinical guidelines indicate that symptom-based empiric antimicrobial treatment of premenopausal women, without obtaining a culture, is a reasonable first approach.1 2 Midstream urine cultures are noninvasive, easy to perform and could potentially enhance antibiotic stewardship. Nevertheless, the value these tests add to the treatment of patients at the initial presentation of symptoms is unclear. Clinical situations in which a urine culture is indicated include: patients with symptoms that recur within 2–4 weeks of a previous similar episode, especially with recent exposure to antimicrobial therapy; patients with unclear history or atypical symptoms; patients with any factors that would place them in a ‘complicated’ category (eg, signs or symptoms of upper tract infection, diabetes, anatomic or functional changes of the urinary tract). It is also important to keep in mind that the study’s results may not apply to acute cystitis in adolescent, pregnant or postmenopausal women. It is notable that a significant proportion of study participants (26%) did not have culture-proven bacterial cystitis, based on the catheterised urine sample. The authors attribute this to possible urethritis or noninfectious causes. As mentioned elsewhere, these results suggest that a substantial proportion of women presenting with symptoms of acute cystitis may ultimately be found to have another aetiology for the symptoms.3 This reinforces the standard recommendation to obtain a urine culture in all patients with acute cystitis symptoms who do not respond promptly to empiric antibiotic therapy. Competing interests None.
Findings The median age of participants was 22 years; 73% were white. At least one organism was cultured from 99% of midstream specimens and 74% of catheter specimens. Escherichia coli was found in 132 episodes (65%). In 120 of 131 episodes (92%), E coli grew in midstream and catheter cultures. Of 114 episodes in which E coli grew with any other organism in midstream samples, 104 (91%) showed E coli growth in catheter urine cultures. E coli colony counts in midstream urine and catheter urine were strongly correlated (r=0.944). Strong correlations (r=0.999) were also found for Klebsiella pneumonia (10 episodes) and Staphylococcus saprophyticus (6 episodes). Positive predictive values (PPV) for E coli in voided
References 1. Grabe M, Bjerklund-Johansen T, Botto H, et al. Uncomplicated UTIs in adults. In: Guidelines on urological infections. Arnhem: European Association of Urology, 2011:15–27. 2. Bent S, Nallamothu B, Simel D. Does this woman have an acute uncomplicated urinary tract infection? J Am Med Assoc 2002;287:2701–10. 3. Donnenberg MS. Uncomplicated cystitis–not so simple. N Engl J Med 2013;369:1959–60.
Evid Based Med August 2014 | volume 19 | number 4 |
151
Copyright of Evidence Based Medicine is the property of BMJ Publishing Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
