Objectives: Current outpatient diagnostic algorithms for urinary tract infection (UTI) in older adults require the presence of classic signs and symptoms of UTI, such as fever and genitourinary symptoms. However, older adults with UTI may present with atypical signs and symptoms. The objective was to identify the associations of age and nursing home status with the clinical presentation of emergency department (ED) patients diagnosed with UTI.Methods: This was a retrospective, cross-sectional analysis of the 2001-2008 National Hospital Ambulatory Medical Care Survey (NHAMCS), ED component. Participants were adult ED patients diagnosed with UTI. Outcome variables were presence of fever, altered mental status, and urinary tract symptoms. Multivariable logistic regression models were constructed for each outcome. Age and nursing home status were the independent variables of interest. Age was divided into adults 18 to 64 years, older adults 65 to 84 years, and oldest adults 85 years of age and older.Results: There were 25.4 million ED visits in which UTI was diagnosed from 2001 through 2008, including 5.0 million in older adults and 2.2 million in the oldest adults. Fever was present in 13% of adults, 21% of older adults, and 19% of the oldest adults. Altered mental status was present in 1% of adults, 7% of older adults, and 13% of the oldest adults. Urinary tract symptoms were identified in 32% of adults, 24% of older adults, and 17% of the oldest adults. In multivariable analysis, altered mental status was more common in older adults (odds ratio [OR] = 1.94) and in the oldest adults (OR = 2.49). Urinary tract symptoms were less common in older adults (OR = 0.60) and the oldest adults (OR = 0.48). Nursing home residence was associated with increased fever (OR = 1.63) and altered mental status (OR = 4.79) and with decreased urinary tract symptoms (OR = 0.35).Conclusions: Fever and urinary tract symptoms are absent in a large proportion of adults over 65 years of age diagnosed with UTI in the ED. Age over 65 years and nursing home residence are associated with increased presence of altered mental status and with lack of urinary tract symptoms. Nursing home residence is also associated with increased presence of fever. Emergency physicians (EPs) continue to diagnose UTI in patients without classic symptoms. Diagnostic criteria for UTI among adults 65 years and over specifically designed for use in the acute care setting should be developed and validated to prevent both inappropriate overdiagnosis and underdiagnosis of UTI.