From the Guidelines
The presence of positive nitrites on urinalysis in asymptomatic patients typically indicates asymptomatic bacteriuria, which does not require treatment in most healthy individuals, except for specific populations such as pregnant women and those undergoing urologic procedures, as recommended by the Infectious Diseases Society of America guideline update in 2019 1.
Clinical Context
The significance of positive nitrites on urinalysis in asymptomatic patients is primarily related to the presence of bacteria that can convert nitrates to nitrites, such as E. coli and other gram-negative organisms. This finding suggests asymptomatic bacteriuria, a condition where bacteria are present in the urine without causing symptoms like pain, frequency, or urgency.
Treatment Recommendations
For most healthy individuals, asymptomatic bacteriuria does not require treatment, as it does not typically cause harm and treatment can contribute to antimicrobial resistance 1. However, treatment is recommended for pregnant women and patients undergoing urologic procedures, as they have higher risks of complications. The standard treatment, when indicated, involves antibiotics such as nitrofurantoin, trimethoprim-sulfamethoxazole, or fosfomycin.
Limitations of Urinalysis
The presence of nitrites is not 100% sensitive for detecting all urinary tract infections, as some bacteria do not produce nitrites. Therefore, the clinical context and other urinalysis findings like leukocyte esterase and microscopic examination for white blood cells should be considered for a complete assessment.
High-Risk Populations
Regular follow-up may be necessary for certain high-risk populations, such as those with diabetes, spinal cord injury, or indwelling catheter use, to ensure resolution of bacteriuria and prevent potential complications. The prevalence of asymptomatic bacteriuria varies among different populations, ranging from less than 1% in healthy children to 25-50% in elderly persons in long-term care facilities 1.
Antimicrobial Stewardship
It is essential to consider the potential negative societal consequence of antimicrobial resistance when deciding whether to treat asymptomatic bacteriuria. Antimicrobial stewardship programs have identified the treatment of asymptomatic bacteriuria as an important contributor to inappropriate antimicrobial use, which promotes resistance 1. Therefore, treatment should be reserved for populations with a clear benefit, and alternative approaches, such as watchful waiting, should be considered for others.
From the Research
Significance of Positive Nitrites on Urinalysis (UA) in Asymptomatic Patients
- Positive nitrites on urinalysis are likely more sensitive and specific than other dipstick components for urinary tract infection, particularly in the elderly 2
- In patients with a high probability of urinary tract infection based on symptoms, negative dipstick urinalysis does not rule out urinary tract infection 2
- Positive dipstick testing is likely specific for asymptomatic bacteriuria in pregnancy, but urine culture is still the test of choice 2
- Asymptomatic bacteriuria is common, particularly in older women, and should not be treated with antibiotics 2, 3, 4
- Treatment of asymptomatic bacteriuria with antimicrobial therapy may improve short-term microbiologic outcomes, but the clinical significance is diminished because the effect is not sustained, there is no measurable improvement in morbidity or mortality, and some data indicate that therapy is deleterious 4
Asymptomatic Bacteriuria (ASB) and Urinary Tract Infections (UTIs)
- ASB is a condition in which bacteria are present in a noncontaminated urine sample collected from a patient without signs or symptoms related to the urinary tract 5, 6
- ASB must be distinguished from symptomatic UTI by the absence of signs and symptoms compatible with UTI or by clinical determination that a nonurinary cause accounts for the patient's symptoms 5, 6
- Interactions between the organism, the host, and the bladder environment determine whether bacteriuria leads to ASB or to UTI 6
Treatment of Asymptomatic Bacteriuria
- In most patient groups, treatment of asymptomatic bacteriuria does not confer benefit and can be harmful 6
- Treatment of asymptomatic bacteriuria is associated with a higher occurrence of antibiotic-resistant bacteria, indicating that treatment in women with recurrent UTIs is even potentially dangerous 3
- A change in prescribing behavior for asymptomatic bacteriuria has been achieved through several fairly high-intensity interventions, such as interactive educational sessions for physicians, but whether these improvements persist beyond the study period is not known 6