1280. Acute Uncomplicated Urinary Tract Infections: Towards a Simple Diagnostic Index
Session: Poster Abstract Session: Urinary Tract Infections
Saturday, October 22, 2011
Room: Poster Hall B1
  • bartknottnerus_uti_diagnosis_111018.pdf (38.6 kB)
  • Background: Diagnostic indicators for acute uncomplicated urinary tract infections (UTIs) have been studied in single-test evaluations, implying that a test is compared to a reference standard without taking into account other test results. In practice, however, diagnosis is multivariable and test results are mutually dependent. As a result, fewer tests may be needed.
    We determined the added diagnostic value of indicators from patient history and laboratory investigations taking into account their mutual dependencies.

    Methods: Healthy, non-pregnant women who contacted their family physician with painful and/or frequent micturition, underwent history questions on UTI symptoms and risk factors, urine stick tests, microscopic examination of urinary sediment, and dipslide (= semi-quantitative culture method). Urine samples were immediately refrigerated and used to make a urine culture within 8 hours. The culture result was the binary dependent variable, the other test results were candidate diagnostic indicators. Logistic regression analysis was performed to derive a parsimonious set of indicators. Using the selected indicators, five diagnostic models were composed (see Results).

    Results: 196 patients were included, 120 of whom (61%) had a positive culture (≥103 colony-forming units per milliliter (CFU/mL)). Seven indicators were selected: three history questions (“do you have pain during micturition?”, “do you have any vaginal irritation?”, “do you think you have a bladder infection?”), two urine stick tests (nitrite positive, blood ≥1+), one sediment indicator (>20 leucocytes/high power field), and one dipslide indicator (≥105 CFU/mL). The areas under the receiver operating characteristic (ROC) curves of the five models were: 0.75 (history only), 0.90 (history+stick), 0.92 (history+stick+sediment), 0.93 (history+stick+dipslide), 0.95 (history+stick+sediment+dipslide). Calibration was good: all Hosmer-Lemeshow p-values were greater than 0.09.

    Conclusion: In women with painful and/or frequent micturition, asking three questions and performing a nitrite/blood urine stick test has excellent discriminatory properties. Investigation of sediment and/or dipslide appears to be of little added value.

    Subject Category: J. Clinical practice issues

    Bart Knottnerus, MD1, Suzanne Geerlings, MD, PhD1, Eric Moll van Charante, MD PhD1 and Gerben ter Riet, MD PhD2, (1)Academic Medical Center - University of Amsterdam, Amsterdam, Netherlands, (2)Department of General Practice, Academic Medical Center - University of Amsterdam, Amsterdam, Netherlands


    B. Knottnerus, None

    S. Geerlings, None

    E. Moll van Charante, None

    G. ter Riet, None

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.