This is Part 2 of the blog post on the diagnosis of UTIs. Check out Part 1 here
Urinary tract infection (UTI) is the most common commonly diagnosed infection in the United States. However, a high incidence of diagnoses does not render those diagnoses appropriate. Increasing evidence suggests that this common condition poses a serious diagnostic challenge. Erroneously identified UTIs frequently result in inappropriate treatment, as well as delays in management of the true underlying pathology. In an era where ever more terrifying multi-drug resistant organisms continue to emerge, increasing emphasis is placed on evidence-based practice and antimicrobial stewardship. In the acute care setting, where information is limited and time is scarce, guideline-based management can aid the Emergency Physician (EP) in improving both individual and community-level outcomes.
Despite increased awareness of UTI’s role in antimicrobial stewardship and cost-effective care, leading interest groups have failed to create a consensus definition of UTI. (For an interesting experiment ask your colleagues what they consider diagnostic criteria for UTI, and prepare for wide variability). Generally speaking, UTI is a diagnosis arrived at by two core features: 1) laboratory testing suggestive of infection, of which urine culture is considered gold standard; and 2) clinical symptomatology.
Herein lies a major quandary for the Emergency Physician EP – culture data is not available in a timely fashion, and determining what defines a “symptom” of a UTI is, at best, elusive. In the absence of culture data, the EP must rely upon a urinalysis (UA), with or without microscopy, as a surrogate. Certain elements of the UA are thought to be particularly predictive of a true infection, including leukocyte esterase, nitrite, white blood cells, red blood cells, and bacteria. However, when considered either alone or in combination, there is variable sensitivity and specificity of nearly all elements of a dipstick or UA. Even when both leukocyte esterase and nitrite are present, the sensitivity and specificity is too poor to definitively diagnose or exclude a UTI.
Part of the poor predictive performance of UAs may be attributed to poor collection techniques and the presence of chronic bactiuria. Obtaining a clean-catch sample in the emergency department setting can be a formidable challenge. Studies suggest less than 10% of ED patients use proper midstream clean-catch techniques. Concerningly, 50% of patients with a contaminated urine sample receive inappropriate intervention and antibiotics. Proper education on sampling techniques as well as and in and out catheterization when appropriate, should be routinely employed.
Despite adequate sample collection, UA interpretation is frequently confounded by the presence of asymptomatic bactiuria (ASB). While definitions vary, the Infectious Disease Societies of America (IDSA) define ASB as isolation of a specified quantitative count of bacteria (105 cfu/ml from clean catch specimens) in a patient without symptoms or signs referable to urinary infection, such as frequency, urgency, dysuria, or suprapubic pain. ASB is common in the geriatric population, and prevalence increase with age and in institutionalized patients. ASB, like UTI, will frequently yield a UA positive for bacteria, LE, nitrate, and pyuria, therefore rending the UA of little use in differentiating between these two conditions. Given these considerations, the clinical symptoms become the most important factor in making the correct diagnosis.
When considering the diagnosis of UTI, beginning with an assessment of patient signs and symptoms seems not only rational, but intuitive. However, in the ever-increasing drive for efficiency, UAs are frequently drawn indiscriminately to expedite work-up. In a recent study of patient treated for UTI in an ED population, 2/3 of patients diagnosed with a UTI had a UA collected as part of an order set, often before being evaluated by a clinician. It was also found that antibiotics were administered inappropriately in 59% of those patients, due to lack of clinical signs or symptoms to substantiate a diagnosis of UTI. Going about the diagnostic work-up in a backwards way invites not only anchoring bias when a UA is positive, but places pressure on the clinician to treat a UTI that isn’t. Clinicians require discipline in looking beyond an abnormal UA, and work to objectively determine if the criteria for UTI are met based on symptomatology – or better yet – order UAs only when symptoms warrant further investigation.
Determining what constitutes a symptom – at least a symptom that should prompt a urinalysis – remains controversial. According to the CDC and SHEA guidelines, symptoms consistent with a UTI include fever and lower genitourinary symptoms such as dysuria, urgency, frequency, suprapubic pain, and costovertebral angle discomfort. Noteworthy is the omission of falls, altered mentation, and general malaise in the elderly in the absence of an indwelling catheter. (See the related post: ‘delirium as a symptom of UTI, physiology or pseudoaxiom?’ for further discussion)
According to the most contemporary guidelines, these nonspecific symptoms without localizing symptoms or fever, are no longer sufficient to support the diagnosis of UTI. This represents a shift in not only traditional clinical teaching, but a departure from prior guidelines. This change results from a realization that both asymptomatic bactiuria and altered mentation are prevalent in the geriatric population, and there is a paucity of evidence supporting a causal link between these findings. Despite these new recommendations, altered mentation, confusion, weakness, and falls are among the most frequent reasons for obtaining a UA in the geriatric population. In a population where ASB is prevalent, and procuring a clean urine sample is challenging, geriatric patients are at high risk of morbidity from inappropriate antibiotic therapy and unnecessary testing. Perhaps more concerning is that with a presumptive diagnosis of UTI, little thought may be devoted to other potential diagnoses – at least until the patient fails to improve.
Over 50 million U.S. adults > 65 years of age (“older adults”), account for over 20 million Emergency Departments (ED) visits each year . Many of these patients have unmet and complex underlying medical needs that are often understated by their chief complaints. The tempting application of traditional ‘one complaint; one algorithm’ approach taught to many emergency physicians, may often result in long-term, downstream, adverse outcomes. One of those relevant to the accompanying blog, is the traditional “if grandma is delirious, look for and treat the UTI” doctrine. A review of the literature proves that the evidence linking UTI’s to delirium in older adults is lacking . Many older adults are bacteriuric; most do NOT have to be treated . The delirium is not a reason to treat bacteriuria . It is also just as likely that it is the other comorbid conditions causing the delirium, since 75% of older adults have two or more comorbid chronic conditions . many of which have the potential to cause delirium at any time. The patient may likely require admission for the delirium, but a more comprehensive investigation into its etiology is more helpful than treating the easy target of a contaminated urine sample
Alexander S Lo, MD, PhD
Assistant Professor of Emergency Medicine, Northwestern University
How to Cite this Post
[Peer-Reviewed, Web Publication] Amick A, Macias M (2018, November 26). The UTI that isn’t: Why a common condition presents such a diagnostic challenge [NUEM Blog. Expert Commentary by Lo A]. Retrieved from http://www.nuemblog.com/blog/uti-part2
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