Do Urine Cultures for Urinary Tract Infections Decrease Follow-up Visits?

Jeremy Daniel Johnson, MD, MPH; Heather M. O'Mara, DO; Hyrum F. Durtschi, DO; Branko Kopjar, MD PhD, MS

Disclosures

J Am Board Fam Med. 2011;24(6):647-655. 

In This Article

Methods

Study Sample

After Madigan Army Medical Center Institutional Review Board and University of Washington Human Subjects Review Committee approval, study participants were obtained through an electronic search of the hospital's electronic medical record (EMR). Inclusion criteria for the study were (1) female sex; (2) age 18 to 65 years; (3) assigned to family medicine at Madigan Army Medical Center; (4) seen in the family medicine clinic from November 1, 2006, to March 25, 2008; and 5) diagnosed with a UTI or acute cystitis.

The exclusion criteria were (1) being pregnant; (2) being diabetic; (3) being diagnosed with a UTI or cystitis during the preceding 6 weeks; (4) being treated with an antibiotic during the preceding 6 weeks; (5) the inability to access medical records to confirm inclusion and exclusion criteria; and (6) having any mention by the medical provider seeing the patient that the patient has a medical condition that qualifies the patient as having a complicated UTI (eg, severe kidney disease).

Because pregnant and diabetic patients are at higher risk for complications from UTI, and because the literature has traditionally excluded one or both of them from studies of uncomplicated UTIs, we also excluded them.[2,15,21–23] We decided to exclude those patients diagnosed with a UTI during the preceding 6 weeks and those treated with an antibiotic during the preceding 6 weeks to avoid patients who may have been incompletely treated or who may have a higher chance of resistant organisms involved with the current infection.

Study Procedures

All patient visits from Madigan's three family medicine clinics were searched electronically to find an International Classification of Diseases, 9th Revision (ICD-9) code match for UTI (ICD-9 code 599.0) and acute cystitis (ICD-9 code 595.0). Patients with either of these two diagnoses who met inclusion criteria and were not excluded based on exclusion criteria were considered to have an uncomplicated UTI for the purposes of the study. The search also was limited to female patients in the study's age range of 18 to 65 years. Patients who had an ICD-9 code diagnosis of UTI or acute cystitis during the previous 42 days (6 weeks) were eliminated according to the third exclusion criteria mentioned above. Patients meeting inclusion criteria were evaluated by one of three researchers using the hospital's EMR.

Every patient had her entire medical visit note from her UTI visit, the EMR list of all diagnoses ever given the patient, the EMR list of all medications ever prescribed to the patient and whether they were dispensed, and her EMR demographic information reviewed for exclusion criteria and all data elements required by the study.

All follow-up visits or phone calls in the 2 weeks after the initial UTI visit, which were recorded electronically, were reviewed. Only those follow-up visits or patient-initiated phone calls in which the subject specifically complained about continued UTI symptoms (dysuria, frequency, urgency, or, rarely, suprapubic pain) were counted toward the study outcomes.

Participants' or their spouses' listed military rank was used as a marker for socioeconomic status. Rank was dichotomized as lower and higher socioeconomic status. To be consistent with previous studies, lower socioeconomic status included the enlisted ranks of enlisted 1 through 4, and all other ranks were considered higher socioeconomic status.[24,25] We used the four racial categories that are found in the EMR demographics section: white, African American, Asian/Pacific Islander, and other race.

Statistical Analysis

Data were collected using SPSS statistical software version 14.0 (SPSS, Inc., Chicago, IL). All patients with a diagnosis of UTI or acute cystitis during the approved study period were reviewed in alphabetical order (to exclude duplicates). We reviewed 1199 records before stopping per institutional review board requirements because we had enough patients to meet 80% power, which left 241 patients unevaluated. Data quality was assured through several audits. We had greater than 98.5% accuracy on all audits. All errors discovered in the audits were corrected before data analysis.

The design of this study was a retrospective cohort study. Power analysis was done at the beginning of the study. We wanted to see if ordering a urine culture would decrease follow-up visits from 8.7% to 3.7% (a 5% drop), which we thought would be clinically meaningful. Our sample size of 779 patients provided a power of 81% at an α error level of 5%.[26,27]

The statistical method used to evaluate the main outcome measure (Is ordering a urine culture associated with a decrease in follow-up visits?) was the χ2 test with a two-tailed P = .05. Multivariate logistic regression was also used with covariates of age (continuous scale); provider status (allopathic/osteopathic physicians [doctor of medicine/doctor of osteopathic medicine] vs midlevel provider); clinic; socioeconomic status; whether medication prescription was filled at the pharmacy; initial antibiotic used to treat the UTI; urine culture ordered; participant status as active duty soldier or civilian family member; and trimethoprim/sulfamethoxazole (TMP-SMX) allergy. Because race data were available in only 65% (512 of 779) of the patients, we did not use race in the multivariate analysis; it would have excluded 35% of the patients from the analysis. When race was added to the multivariate analysis, the results were unchanged overall. When fever, costovertebral angle tenderness, and nausea were included in the multivariate analysis, 331 cases had to be excluded because of missing data; thus, we did not include them in the final multivariate analysis. Of note, however, when these three characteristics were added, the results were unchanged overall.

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