Evaluation of Common Genitourinary Infections
One woman in four will have at least one urinary-tract infection (UTI) during her lifetime, and 75% will have at least one vaginal yeast infection.[84,85] Recurrence of both types of infections is very common and results in millions of physician office visits annually. Symptoms of UTIs and yeast infections are often vague and are similar to those of other disorders and infections. Some patients with yeast infections may be asymptomatic. Clinicians frequently use rapid-testing methods to aid in diagnosis of these disorders. Since 1986, several types of FDA-approved urine-dipstick tests have been available for home use ( Table 5 ). FDA approved the marketing of two vaginal pH tests, pHEM-Alert (Femtek) and Fem-V (originally approved as VI-SENSE, Synova), for home use in 2001 and 2006, respectively.
UTI Test Devices. Older UTI tests, such as the First Response Uriscreen test (Carter–Wallace), detected the presence of catalase produced by bacteria and white blood cells. Newer urine dip-sticks are designed to detect leukocyte esterase (LE), nitrites, blood, and protein. The patient either dips the stick into a cup of collected urine or holds the strip in the urine stream for 1–10 seconds. The result should be read within one to two minutes. The reagent pad is acidic, and the presence of protein, which is more basic, will cause a pH change and therefore a color change. If nitrites are present they will react with arsanilic acid and produce a color change (e.g., pink). If LE is present it will cause a hydrolysis reaction with an amino acid ester, which produces a pyrrole, which then reacts with diazonium salts to produce a color change (e.g., purple).
Vaginal pH Kits. These tests employ litmus paper to test the pH of the vagina. The normal vaginal environment is acidic (pH 4–4.5). Studies have shown that an elevated vaginal pH is an excellent way to differentiate between candidiasis and bacterial vaginitis (BV) or trichomoniasis vaginalis (TV).[87,88] Pavletic et al. found that an abnormal pH (>4.5) was significantly (p < 0.001) associated with BV, TV, or a mixed infection in a study in 443 women. To use the pHEM-Alert kit, the patient inserts the swab into the lower vagina and, after two seconds, compares the color of the sample with a pH test chart. The Fem-V test uses a panty liner with a yellow litmus paper strip in the center of the liner. The patient wears the liner until discharge occurs or for 6–12 hours. The patient then removes the indicator strip and places it in the drying tray provided. The strip should be allowed to dry for 10 minutes. A blue or green stain remaining after 10 minutes indicates an abnormal pH and the need for the patient to contact a health care provider.
The literature suggests that patients with recurrent symptoms may be the best candidates for home testing.[84,87] Pharmacists should discourage self-testing for first-time UTIs or yeast infections and refer the patient to her provider. If home testing is appropriate for the patient, the pharmacist can help her select a specific test device by discussing personal preferences, cost, and accuracy. Costs of UTI test kits vary ( Table 5 ). pHEM-Alert retails for $36 for 12 tests. Fem-V retails for $7.99 for one kit (one liner and drying tray).
The accuracy of UTI tests has been debated in the literature. Franco cited unacceptable false-negative rates of 40–80% when urine dipsticks were used alone. A 2004 meta-analysis examined 72 studies of nitrite- and LE-based UTI tests and provided guidance on how to improve their performance. For example, the authors found that, in general, nitrite-based tests had low sensitivity (45–60%) and high specificity (85–98%). However, when specific populations were examined, higher levels of accuracy were achieved in elderly, pregnant, and urology patients, although the differences were not significant. LE-based tests had a sensitivity of 48–86% and a specificity of 17–93% and were reported to be less accurate than nitrite tests. The accuracy of LE-based tests was highest when urine was collected from catheterized patients. When kits included both nitrite- and LE-based tests, overall sensitivity and specificity increased and the risk of false negatives was minimized. Pharmacists prefer the combination test.
In view of these findings, patients may want to choose a nitrite- and LE-based UTI test kit. Self-testing for and self-treatment of UTIs have shown to be accurate and beneficial with proper training. In a 2001 study, 172 university students with a history of at least two UTIs were educated about UTI symptoms, taught to obtain a clean-catch urine specimen, and followed for one year. The study found that 94% (95% CI, 90–99%) of the self-identified symptomatic episodes turned out to be UTIs confirmed as such by the research laboratory.
The accuracy of vaginal pH tests has been reported to be very high (sensitivities of 95–100%) when used by clinicians to rule out candidiasis. The sensitivity and specificity of Fem-V have been reported by the manufacturer to be 90.8% and 81.3%, respectively (n = 516). The pHEM-Alert test has also shown good accuracy. In a 2003 study, 96% of patients (144/151) were able to correctly use the test and interpret the results at home, leading to a 50% reduction in inappropriate use of nonprescription antifungal products (p = 0.018). In comparison, a 2002 study found that only 32 (33.7%) of 95 women could correctly self-detect candidiasis from symptoms alone.
Patients should be reminded that UTI and vaginal pH test kits are meant for screening only; clinician input is needed for correct diagnosis and treatment. If the patient is a candidate for home testing, the pharmacist should educate her about device limitations. For example, UTI test kits may produce false-negative results because not all UTI-causing organisms produce nitrites and because LE is a polymorphic enzyme produced by white blood cells and may not be a definitive indicator of UTI. Vaginal pH tests are less likely to give false-negative results, but patients should still be aware of the possibility.
UTI test kits work best with concentrated urine, so pharmacists should encourage patients to use the morning's first urine or to hold their urine for four to six hours. Ingestion of dyes (dietary or pharmaceutical), antibiotic use, and large doses of vitamin C (>250 mg) may cause false-negative results. Also, menstrual blood interferes with UTI and vaginal pH tests, so patients should seek care from their provider if symptoms occur during menstruation.
Proper self-testing for UTIs and yeast infections allows patients to provide objective information to clinicians. This information can help avoid incorrect empirical therapy when patients are triaged via telephone and may even help shorten clinic waiting time.
Am J Health Syst Pharm. 2008;65(4):299-314. © 2008 American Society of Health-System Pharmacists
Cite this: Devices for Home Evaluation of Women's Health Concerns - Medscape - Feb 15, 2008.