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The urinalysis trap
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The easy availability of the urinalysis, usually by dipstick with or without microscopy, has led to its widespread use, often in situations where there is little or no indication for its use. Furthermore, even when indicated for purposes of detecting proteinuria or hematuria or ascertaining specific gravity, there is often the unanticipated finding of pyuria and/or bacteriuria, which then results in further testing or interventions that are usually not indicated.
We do not mean to minimize the diagnostic utility of urinalysis (UA) where indicated for detecting abnormalities such as blood, cellular casts, protein and specific gravity, nor for proving the presence of urinary tract infection in selected cases. However, the UA by dipstick or microscopic examination has become part of routine medical practice and is quite often obtained for no clear clinical indication or as part of the initial “work-up” in patients presenting with a variety of signs and symptoms, which on initial evaluation would appear to have no relationship to the urinary system. Pyuria with or without bacteriuria is frequently present, especially in elderly patients. Pyuria is often an indication of asymptomatic bacteriuria (ASB) or contamination with vaginal secretions. It is often the impetus for obtaining a urine culture. In the absence of pregnancy or impending urological surgery, the finding of ASB in adults (including those with diabetes) is inconsequential and should not be sought nor treated. In fact, the detection of clinically irrelevant pyuria or bacteriuria in the UA may serve not only to potentially delay making the correct diagnosis, but frequently leads to the prescribing of antimicrobial agents for the treatment of ASB, thereby acting in direct violation of the efforts put forth in antimicrobial stewardship programs. Additionally, this unwarranted practice often leads to preventable complications, increases length of hospital stays and provides the clinician with a false sense of accomplishment.
The prevalence of ASB has been found to be dependent upon factors such as age, sex and genitourinary abnormalities. The prevalence of ASB in young nonpregnant women is generally 1% to 3%, at least 10% in men aged 65 years and older and at least 20% in women aged older than 65 years. ASB is very common in long-term care facilities with a prevalence of 15% to 30% in men and 25% to 50% in women. Although women with ASB are at an increased risk for symptomatic UTIs, it is clear from many published studies that treating adults with ASB with antibiotics offers no beneficial health outcome. Moreover, the risk for future symptomatic urinary infections is not decreased. In fact, it was demonstrated recently that treatment of ASB in adult nonpregnant women is harmful, resulting in increased numbers of symptomatic infections and causing more antibiotic resistance of infecting organisms in those who go on to develop symptomatic UTI.
The Infectious Diseases Society of America, reiterated in the American Board of Internal Medicine’s “Choosing Wisely” campaign, has firmly recommended against the screening for, and treatment of, ASB. Nonetheless, on a daily basis this practice continues in the various venues where patients receive their medical care and in long-term care facilities. Even though the presence of pyuria that usually accompanies ASB does not imply that antibiotics are necessary, these drugs are frequently prescribed, in large part due to a faulty rationale driven by white blood cells (WBCs) observed in the UA regardless of why it was obtained. For reasons that are unclear, when the UA demonstrates a predetermined quantity of WBCs or bacteriuria, the practice of reflex urine culture is policy protocol in many hospital clinical laboratories, even under those circumstances when the indication for the UA was not infection-related.
There are populations that warrant searching for and treating ASB based on convincing studies, such as pregnant women and those undergoing invasive urologic procedures. It has been demonstrated in studies conducted decades ago that pregnant bacteriuric women not only have a greatly heightened risk for pyelonephritis, but that the pyelonephritis increases the chance of preterm delivery and low-birth weight infants. Hence, routine screening and treatment of bacteriuria beginning in early pregnancy and periodically after therapy is still the standard of care despite a recent study questioning this practice. Likewise, the greater incidence of systemic infection and bacteremia following invasive urologic interventions in those patients with ASB is the basis for the prudent practice of preprocedure screening and administering treatment if significant bacteriuria is uncovered. However, the decision to do the same with orthopedic surgeries has come under significant question as the protective value of what seems to be a common practice has not been well-defined.
In addition to wasting resources and encouraging the emergence of antibiotic-resistant organisms, searching for pyuria/ASB can result in harm to the patient with toxicity from unindicated antimicrobial therapy and urologic referrals and procedures. Another problem is the misdirection often occurring among elderly patients hospitalized for high fever, coma or other nonspecific signs or symptoms. The tendency to focus on the finding of pyuria or bacteriuria may delay the true diagnosis in a critically ill patient said to have “urosepsis.” A typical example is the elderly female nursing home patient admitted to the hospital with fever, confusion and dehydration. The finding of ASB, which has at least a 30% chance of being present, translates to urosepsis until hydration clarifies the presence of pneumonia. One of us vividly remembers an elderly woman who fit that description and was treated for urosepsis until someone finally did a real physical examination and found the cellulitis she had on her leg.
The bottom line is that the finding of pyuria/ASB in a nonpregnant adult in a “routine” UA should almost always be ignored. Additionally, in a seriously ill patient without symptoms of UTI, it is necessary to look beyond the finding of pyuria/ASB to make a diagnosis.
- References:
- ABIM Foundation. Choosing Wisely. Antibiotics: When you need them—and when you don’t. http://www.choosingwisely.org/patient-resources/antibiotics/. Updated February 26, 2014. Accessed August 16, 2016.
- Cai T, et al. Clin Infect Dis. 2012;doi:10.1093/cid/cis534.
- Cai T, et al. Clin Infect Dis. 2015;doi:10.1093/cid/civ696.
- Kazemier BM, et al. Lancet Infect Dis. 2015;doi:10.1016/S1473-3099(15)00070-5.
- Nicolle LE. Curr Opin Infect Dis. 2014;doi:10.1097/QCO.0000000000000019.
- Nicolle LE, et al. Clin Infect Dis. 2005;doi:10.1086/427507.
- Nicolle LE. Lancet Infect Dis. 2015;doi:10.1016/S1473-3099(15)00145-0.
- For more information:
- Larry M. Bush, MD, FACP, is an affiliated professor of biomedical sciences at the Charles E. Schmidt College of Medicine, Florida Atlantic University, and affiliated associate professor of medicine at the University of Miami-Miller School of Medicine, Palm Beach County, Florida.
- Donald Kaye, MD, MACP, is a professor of medicine at Drexel University College of Medicine, associate editor of the International Society for Infectious Diseases’ ProMED-mail, section editor of news for Clinical Infectious Diseases and an Infectious Disease News Editorial Board member.
- Maria T. Vazquez-Pertejo, MD, FCAP, is the director of the department of pathology and laboratory medicine, BlueHealth, at Wellington Regional Medical Center, Palm Beach County, Florida.
Disclosures: Bush, Kaye and Vazquez-Pertejo report no relevant financial disclosures.