Rosa Morros

Background Most guidelines recommend a midstream urine (MSU) or a midstream clean-catch (MSCC) sample for urinalysis. However, whether this sample is better than others is still controversial. Objectives To assess the most adequate non-invasive method to collect a urine specimen for diagnosing urinary tract infections (UTI) in symptomatic non-pregnant women. Methods This review was conducted according to the Systematic Reviews of Diagnostic Test Accuracy guidelines (PROSPERO CRD42021241758). PubMed was searched paired sample studies and controlled trials. Studies comparing MSCC, MSU without cleaning, first-void urine, and random voiding samples were considered. Studies evaluating invasive methods were excluded. The main outcome was diagnostic accuracy of urine cultures. Contamination rates were evaluated. The risk of bias tool for systematic reviews on diagnostic accuracy (QUADAS-2) was assessed. Results Six studies including 1,010 patients were evaluated. Only two studies used paired samples. No study was considered as having low risk of bias. There was no difference in contamination for MSU specimens collected with or without cleansing and between random void urine collection and MSCC. In one study comparing first-void urine with MSU samples, the contamination rate was lower in the latter, but the gold standard of urine culture was only used for one sampling collection. Conclusions To the best of our knowledge, this systematic review is the first to assess the evidence available from different exclusively non-invasive urine sampling. Despite being widely recommended, our review did not find consistent evidence that asking women to provide midstream samples with or without cleansing is better.