From the Guidelines
For a simple uncomplicated urinary tract infection (UTI) in women, a urinalysis with microscopy is the primary laboratory test to order, but it is not always necessary as diagnosis can often be made based on symptoms alone 1. When considering laboratory tests for a simple UTI in females, it's essential to weigh the benefits of testing against the potential for unnecessary antibiotic use and resistance.
- A urine culture is not routinely necessary for uncomplicated UTIs but may be ordered if there are concerns about antibiotic resistance, recurrent infections, or complicated UTI factors 1.
- In some cases, a point-of-care dipstick test may be sufficient for diagnosis, detecting leukocyte esterase (indicating white blood cells) and nitrites (suggesting gram-negative bacteria) 1.
- Blood tests are generally not needed for simple UTIs unless there are signs of systemic infection or kidney involvement. Key considerations for ordering laboratory tests in simple UTIs include:
- The patient's symptoms and medical history
- The presence of risk factors for complicated UTI
- The potential for antibiotic resistance
- The need for prompt diagnosis and treatment to prevent complications and improve quality of life 1. It's also important to note that routine post-treatment urinalysis or urine cultures are not indicated for asymptomatic patients 1, and that treatment should be guided by the patient's symptoms and medical history, rather than solely by laboratory test results.
From the Research
Laboratory Tests for Simple Urinary Tract Infection (UTI) in Females
- Urine culture with >10^5 colony-forming units/mL (CFU/mL) in symptomatic patients is considered the diagnostic "gold standard" for UTI 2
- Urinalysis, including nitrite dipstick and leukocyte esterase test, can be used to diagnose UTI, with a positive nitrite reaction being a useful indicator of UTI 3, 4, 5
- Leukocyte esterase and blood reaction on urine dipstick can be used to rule out UTI, with a negative result having a high negative predictive value 3, 5
- Pyuria (presence of white blood cells in urine) and bacteruria (presence of bacteria in urine) can also be used to diagnose UTI, with moderate pyuria and bacteruria being good predictors of UTI 5
- The choice of urine sample collection method (e.g. midstream urine, midstream clean-catch, first-void urine, random voiding) does not appear to significantly affect diagnostic accuracy 6
Urine Sample Collection Methods
- Midstream urine (MSU) or midstream clean-catch (MSCC) sample collection is commonly recommended, but the evidence for its superiority over other methods is limited 6
- First-void urine and random voiding samples may be equivalent to MSU or MSCC samples in terms of diagnostic accuracy 6
- The contamination rate of urine samples does not appear to be significantly affected by the collection method 6