What tests should be ordered for a patient presenting with symptoms of a urinary tract infection (UTI) or interstitial cystitis?

Diagnostic Tests for Urinary Tract Infection (UTI) and Interstitial Cystitis (IC/BPS)

For patients presenting with symptoms of urinary tract infection or interstitial cystitis, the minimum laboratory evaluation should include urinalysis for determination of leukocyte esterase and nitrite level by dipstick and microscopic examination for WBCs, with urine culture ordered only if pyuria or positive leukocyte esterase/nitrite is present. 1

Initial Diagnostic Tests for UTI

Basic Testing

• Urinalysis with dipstick testing for leukocyte esterase and nitrite is the first-line test for all patients with suspected UTI 1
• Microscopic examination for WBCs (≥10 WBCs/high-power field indicates pyuria) should be performed 1
• Urine culture with antimicrobial susceptibility testing should only be ordered if pyuria is present or leukocyte esterase/nitrite test is positive 1

Specimen Collection

• For men: Obtain a midstream or clean-catch specimen when possible; alternatively, use a freshly applied clean condom external collection system with frequent monitoring 1
• For women: Obtain a midstream clean-catch specimen with careful perineal cleaning; if not possible, in-and-out catheterization may be necessary 1, 2
• For patients with indwelling catheters: Change the catheter prior to specimen collection if urosepsis is suspected 1

Additional Testing for Complicated Cases

• Complete blood count with differential may be indicated if systemic infection is suspected 1
• Blood cultures should be considered only if bacteremia or urosepsis is suspected (fever, shaking chills, hypotension, or delirium) 1
• Imaging studies are generally not needed for uncomplicated UTI but should be considered for patients with suspected pyelonephritis who remain febrile after 72 hours of treatment 1

Diagnostic Tests for Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS)

Initial Evaluation

• Urinalysis and urine culture to rule out UTI, as symptoms can overlap significantly 1, 3
• Documentation of basic symptoms including number of voids per day, sensation of constant urge to void, and the location, character, and severity of pain 1
• Assessment for dyspareunia, dysuria, and in men, ejaculatory pain 1

Specialized Testing

• Cystoscopy is recommended for patients with suspected Hunner lesions, as this is the only reliable way to diagnose their presence 1
• Cystoscopy may be performed under general anesthesia if the patient cannot tolerate office flexible cystoscopy 1
• Baseline voiding symptoms and pain levels should be documented to measure subsequent treatment effects 1
• A one-day voiding log at minimum should be used to establish the presence of low volume frequency voiding 1

Tests to Rule Out Other Conditions

• Proper hematuria workup should be performed in patients with unevaluated hematuria 1
• Brief neurological examination to rule out occult neurologic problems 1
• Evaluation for incomplete bladder emptying to rule out occult retention 1
• Urodynamic testing is not recommended for routine clinical use to establish an IC/BPS diagnosis but may be useful if outlet obstruction or poor detrusor contractility is suspected 1

Diagnostic Algorithm

1. Initial Assessment:

   • Urinalysis with dipstick for leukocyte esterase and nitrite 1, 2
   • Microscopic examination for WBCs 1

2. If positive for infection markers (positive leukocyte esterase, nitrite, or ≥10 WBCs/HPF):

   • Order urine culture with antimicrobial susceptibility testing 1
   • Treat as UTI if culture confirms infection 1

3. If negative for infection markers or persistent symptoms despite treatment:

   • Consider IC/BPS diagnosis if symptoms have been present for at least six weeks with documented negative urine cultures 1
   • Document voiding frequency, pain characteristics, and urge sensation 1
   • Consider cystoscopy, especially if Hunner lesions are suspected 1

4. For recurrent or complicated cases:

   • Consider additional testing including imaging studies to rule out structural abnormalities 1
   • Evaluate for comorbid conditions that may mimic or exacerbate symptoms 3, 4

Common Pitfalls to Avoid

• Treating asymptomatic bacteriuria, which is not recommended 1
• Failing to distinguish between UTI and IC/BPS, which have overlapping symptoms but different treatments 3, 5
• Treating based on contaminated specimens, which leads to unnecessary antibiotic use 2
• Missing Hunner lesions in IC/BPS patients, who typically respond well to targeted treatment 1
• Overreliance on nitrite testing alone, which has excellent specificity but limited sensitivity 2
• Assuming all urinary symptoms with negative cultures are IC/BPS without considering other conditions like overactive bladder 3, 6

Remember that while UTI is caused by bacterial infection and responds to antibiotics, IC/BPS is a chronic inflammatory condition that requires different management approaches and does not respond to antibiotic therapy 4, 5, 7.