Detection of urinary tract infection (UTI) in long-term care setting: Is the multireagent strip an adequate diagnostic tool?

Urinary tract infection (UTI) is one of the most commonly diagnosed and treated infection in elderly residents of long-term care (LTC) setting, and most of them are asymptomatic. Early diagnosis and treatment especially in this group of patients is very important because even a brief delay contributes to mortality as well as to reduce functional and cognitive decline. The purpose of the present study was to determine the validity of multireagent strips (Multistix 10 SG, Bayer, UK) compared with standard urinalysis for the early detection of UTI in LTC elderly patients. Urine specimens were examined for the presence of leukocyte esterase (LE) activity as an indicator of pyuria, nitrite production as an indicator of bacteriuria, erythrocytes (RBC), and protein. The sensitivity, specificity, predictive value, kappa agreement, and likelihood ration were determined for each of the four dipstick parameters measurement separately, and in four combinations were calculated against the urine culture for the diagnosis of UTI and asymptomatic bacteriuria. Ninety-six patients aged 65 years and older with symptomatic UTI were compared with similar number, age, sex and comorbidity status matched patients with asymptomatic bacteriuria. In both groups, urinary culture results were compared with the results of multireagent strips. The multireagent strips results were evaluated for the presence of LE activity as an indicator of pyuria, nitrite production as an indicator of bacteriuria, RBC, and protein. All positive sticks results were evaluated as single parameter and in combination of them. Positive urine cultures were found in 71% (68/96) of the patients with symptomatic and in 60% (58/96; p>0.05) of patients with asymptomatic UTI. In patients with UTI, using multireagent strips kappa agreement for LE was 0.53, for nitrite was 0.14, and in combination of them was 0.31. Similar results were reported in patients with asymptomatic bacteriuria, 0.35, 0.23, and 0.35m. The detection of RBC and protein, as single parameter or in combination with other parameters, decreases accuracy of the tests. Positive dipstick tests for LE and/or nitrite are not specific indicators of UTI, and are not suitable for screening of LTC inpatients for UTI because of high false-negative rates of the LE and nitrite.