Cut-off values to rule out urinary tract infection should be gender-specific

Abstract

The diagnosis of urinary tract infection (UTI) by urine culture is an expensive and time-consuming procedure. Using a screening method, to identify negative samples, would improve the procedure and reduce costs. In this study, urine flow cytometry, of over 7000 urine samples, was assessed by retrospective analysis. With a cut-off value of >200bacteria/μl, we obtained a sensitivity of 93.0%, a specificity of 63.5%, and a negative predictive value (NPV) of 96.2%. As a result the culturing of 49% of all samples could be avoided. In addition, the data was retrospectively analyzed to determine if the introduction of gender-specific cut-off values could improve screening results. The obtained receiver operator curves are indeed significantly different when gender specific cut-offs were used. When a NPV of 95% is considered acceptable the unisex cut-off value of >200bacteria/μl can be used for women (NPV 94.9%), but the cut-off value for men could be raised to >400bacteria/μl without diminishing the NPV (NPV 95.0%).

Influence of gender on the performance of urine dipstick and automated urinalysis in the diagnosis of urinary tract infections at the emergency department

“…Therefore, gender-specific bacterial and leucocyte cut-offs are needed to mainly improve the diagnostic performance in men. This view is also supported by other studies concerning the UF-1000i and its precursor, the UF-500 [15][16][17]. In addition, focusing on cut-off values based on the highest possible accuracy also showed that in men a higher overall accuracy existed at lower cut-off values for both UF-1000i leucocyte and bacterial count, reflecting better specificity in men compared to women for both parameters.…”

“…adequately analysed in the ED setting. Most gender-related studies are situated in the primary care, patient populations are insufficiently described and comparison between genders is lacking [10][11][12][13][14][15][16][17][18][19]. In addition, in contrast to the ED, the majority of cases in the primary care setting are women [3,20].…”

Automated Flow Cytometry: An Alternative to Urine Culture in a Routine Clinical Microbiology Laboratory?

“…These will be chosen depending on the characteristics of the analyzed population, which is usually heterogeneous. Furthermore, published data recommended adjusting the cutoff values according to gender and age of the patients to increase detection reliability [ 15 , 23 , 31 , 51 ].…”

Performance of urinalysis tests and their ability in predicting results of urine cultures: a comparison between automated test strip analyser and flow cytometry in various subpopulations and types of samples

“…In men, leucocyte esterase was also highly sensitive that can be used to rule out UTIs. It has been proposed that the cut-off of positive urine cultures in men and women should be different,15 and our study showed the difference in the performance in urinalysis tests in men and women. We believe that the classic cut-off for positive urine culture, that is, 10 5 CFU/mL, is the most robust since in general the results of the tests were applicable in various subpopulations, and when additional demographic information is available, a more precise interpretation of urinalysis tests can be made.…”

“…Previous urinalysis studies were performed in one specific population such as paediatric and women5 13 or in the whole population without subanalysis on specific subpopulation 14. A comparison of the performance of the urinalysis tests in various subpopulations is therefore difficult15 because studies need to be compared that used difference instruments 16. Despite the long history of the use of urinalysis in documenting UTIs, and despite the renewed interest in urinalysis, no studies have been published on a head-to-head comparison of urinalysis by automated test strip analyser with urinalysis by automated cell count using flow cytometry.…”