From the Guidelines
A nitrite positive urine test is highly suggestive of a urinary tract infection (UTI), but it is not definitive and should be considered in conjunction with other symptoms and urinalysis findings. Nitrites in urine typically indicate the presence of bacteria that convert dietary nitrates to nitrites, particularly gram-negative bacteria like E. coli 1. The presence of either nitrite or leukocyte esterase has a sensitivity of 88% and a false positive rate of 7% for urinary tract infection, and if both tests are positive, the specificity is 96% 1. Some key points to consider when interpreting a nitrite positive urine test include:
- The nitrite test has high specificity but lower sensitivity, meaning that a positive result is more likely to be a true positive, but a negative result does not rule out a UTI 1
- The presence of symptoms such as burning during urination, frequency, urgency, or pelvic pain, as well as other urinalysis findings like leukocyte esterase or bacteria seen on microscopy, are important considerations in diagnosing a UTI
- Some UTI-causing organisms do not produce nitrites, and false negatives can occur with insufficient bladder time or low dietary nitrate intake
- If a nitrite positive test is accompanied by symptoms, treatment with antibiotics such as nitrofurantoin, trimethoprim-sulfamethoxazole, or fosfomycin may be prescribed, depending on the individual's specific situation and medical history 1. It is essential to consult a healthcare provider for proper diagnosis and treatment, and to drink plenty of water and urinate frequently to help flush bacteria from the urinary tract.
From the Research
Nitrite Positive Urine and UTI
- A nitrite positive urine test result can indicate the presence of a urinary tract infection (UTI), but it is not a definitive diagnosis 2.
- Nitrites are more sensitive and specific for UTI, particularly in the elderly, compared to other dipstick components 2.
- However, a positive nitrite test result does not necessarily mean that the patient has a UTI, as other factors can influence the result 3.
- The presence of nitrites in urine is often used as an indicator of bacterial infection, but it is not a reliable method for guiding antimicrobial therapy 3.
Diagnostic Considerations
- Urine culture is the gold standard for detecting UTI, and it is recommended to perform a urine culture in cases where the probability of UTI is moderate or unclear 2.
- Dipstick urinalysis, including nitrite testing, should be interpreted in the context of the patient's symptoms and pretest probability of UTI 2.
- Asymptomatic bacteriuria is common, particularly in older women, and should not be treated with antibiotics unless the patient is symptomatic 2.
Treatment Considerations
- First-line treatments for UTI include nitrofurantoin, fosfomycin, and trimethoprim-sulfamethoxazole, which have minimal collateral damage and resistance 2, 4, 5.
- The choice of antimicrobial therapy should be based on factors such as pharmacokinetics, spectrum of activity, resistance prevalence, and potential for adverse effects 4.
- Patient-specific risk factors, such as prior urinary infection or colonization with resistant Enterobacteriaceae, can predict trimethoprim/sulfamethoxazole resistance in community-onset UTI 6.