Diagnostic Testing for 16-Year-Old with Dysuria and Frequency
Order a urinalysis with microscopy and urine culture simultaneously to evaluate for urinary tract infection, as this is the most common cause of dysuria and frequency in adolescents. 1
Initial Laboratory Testing
Urinalysis with Microscopy
- Obtain urinalysis testing for leukocyte esterase, nitrite, and microscopic examination for white blood cells. 2
- A negative dipstick for both leukocyte esterase and nitrite combined with negative microscopy has a 95-98% negative predictive value for UTI. 2
- The presence of pyuria (≥10 WBCs/high-power field) or positive leukocyte esterase indicates likely infection requiring culture confirmation. 2
- Urinalysis alone is insufficient to rule out UTI, as 10-50% of culture-proven UTIs can have false-negative urinalysis results. 2
Urine Culture
- Send urine culture concurrently with urinalysis rather than waiting for urinalysis results, given the logistic difficulty of obtaining culture after the office visit and the inability of rapid methods to exclude infection with 100% certainty. 2
- Culture is essential for identifying the causative organism (most commonly E. coli) and guiding antibiotic therapy if needed. 3, 4
Specimen Collection Method
- Obtain a clean-catch midstream urine specimen for this ambulatory adolescent patient. 2
- Catheterization is not necessary in a cooperative adolescent who can provide an adequate clean-catch specimen, though it offers higher sensitivity (95%) and specificity (99%) if the initial specimen is contaminated or results are equivocal. 2
Additional Considerations
When Further Testing Is NOT Needed
- More invasive tests like renal ultrasound or voiding cystourethrogram are NOT indicated unless specific red flags are present, including: 2
- Recurrent UTIs
- Abnormal voiding patterns beyond simple frequency
- Positive findings on urinalysis suggesting upper tract involvement
- Hematuria with proteinuria or red blood cell casts 2
Clinical Assessment Points
- Evaluate for sexual activity history, as this is the strongest predictor of recurrent UTIs in young women and may influence management. 4
- Assess for vaginal symptoms (discharge, irritation), as their presence with dysuria suggests vaginitis rather than UTI and would require different evaluation. 3
- Screen for hypercalciuria (spot urine calcium-to-creatinine ratio) only if symptoms persist despite negative cultures or if there is isolated frequency without clear infectious etiology. 2, 5
Common Pitfalls to Avoid
- Do not treat empirically without obtaining urine culture in adolescents, even if urinalysis is positive, as culture guides appropriate antibiotic selection and documents the infection. 6
- Do not order imaging studies initially unless there are concerning features suggesting complicated infection or anatomic abnormalities on history and physical examination. 2
- Do not rely solely on dipstick results for treatment decisions, as both overtreatment (47%) and undertreatment (13%) rates are significant when using dipstick alone. 7