Can urine cultures and reagent test strips be used to diagnose urinary tract infection in elderly emergency department patients without focal urinary symptoms?

Abstract

Objective:To compare the results of urine cultures and reagent strip testing in 2 groups of elderly emergency department (ED) patients: an asymptomatic group unlikely to have urinary tract infection (UTI), and a group who had vague symptoms and were considered at risk for UTI. Methods: We performed a prospective observational convenience study with 2 groups of 100 patients aged 65 or older. The asymptomatic group consisted of afebrile patients presenting to the ED with non-infectious complaints, while the symptomatic group included patients presenting with acute confusion, weakness or fever but no apparent urinary symptoms. We defined a positive urine culture as a single organism count greater than 100 000 CFU/mL in mid-stream specimens, or greater than 1000 CFU/mL in catheter specimens. We considered reagent strips positive if they demonstrated any reaction to the leukocyte-esterase assay, the nitrite assay or both. Results: Of the 33 positive cultures, 10 had negative reagent strips. Thirteen of the 14 positive nitrite tests were culture positive for a specificity of 92.8% and a sensitivity of 36.1%. Positive cultures did not infer a diagnosis of UTI. Of the 67 positive reagent strips, 41 (61.2%) were associated with negative cultures. Likelihood ratios (LRs) in both groups affirmed the inability of the reagent strips to help significantly in decision making, with positive and negative LR in the indeterminate range (control group: 2.8 and 0.31, symptomatic group: 2.7 and 0.46, respectively). Conclusion: In the elderly, reagent testing is an unreliable method of identifying patients with positive blood cultures. Moreover, positive urine culture rates are only slightly higher in patients with vague symptoms attributable to UTI than they are in (asymptomatic) patients treated for non-urologic problems, which suggests that many positive cultures in elderly patients with nonfocal systemic symptoms are false-positive tests reflecting asymptomatic bacteriuria and not UTIs. Blood cultures, regarded by many as the criterion standard for UTI, do not have sufficient specificity to confirm the diagnosis of UTI in elderly patients with non-specific symptoms.

Precisão da tira reagente e do exame microscópico da urina no diagnóstico de infecções do trato urinário em porcas

“…There are several studies which evaluate the sensitivity and the specificity of the positive reaction for nitrite in the reagent strip for UTI diagnosis in human beings (Bollan et al 1989, Tincello & Richmond 1998, Sultana et al 2001, Devillé et al 2004, Ali et al 2007, Ducharme et al 2007, Taneja et al 2010. The values found range from 33 to 57% and 78 to 99%, respectively.…”

Kan vi stole på urinstiks?

“…Resultatene blir fremstilt i prosent, slik at en feilfri urinstiks ville vist en sensitivitet, spesifisitet, PPV og NPV på 100 prosent. Tabell 3 er en sammenstilling av resultatene for sensitivitet, spesifisitet, PPV og NPV i de inkluderte studiene (21)(22)(23)(24)(25)(26).…”

“…Til tross for at en urinstiks ikke kan skille mellom en ASB og en UVI, er det vanlig å bruke urinstiks for å diagnostisere UVI hos eldre pasienter. I de fleste tilfeller er urinstiks hyppig brukt i klinikken, og oppstart av antibiotika kan skje på bakgrunn av en positiv urinstiks frem til et dyrkingssvar av urinprøve eventuelt foreligger (26). Ettersom urinstiks tilsynelatende er mye brukt i klinikken og resultatet av urinstiks har en avgjørende rolle i diagnostiseringen av UVI hos eldre, er det interessant å se på hvor pålitelig urinstiks er.…”

“…Studiene av nyere dato som er inkludert i denne litteraturstudien (21)(22)(23)26), understreker at urinstiks ikke er et godt nok hjelpemiddel til å fastslå bakteriuri hos eldre pasienter. De viser til resultater hvor det er mange falske positiver og der sensitiviteten og spesifisiteten er lav, det vil si at urinstiks ikke er pålitelig til å skille friske og syke når det gjelder UVI.…”

Falls prevention in primary care

“…It's important to be aware that many older people have asymptomatic bacteriuria. A urine dipstick reading is an unreliable indicator of urinary tract infection in older people 4 and treating an older person for urinary tract infection in the absence of urinary symptoms exposes them unnecessarily to the hazards of antibiotic therapy. Erroneous diagnosis or urinary tract infection also causes delays in finding out the reasons why the person is really falling.…”