What actions should the urinalysis supervisor take in cases of suspected tyrosyluria with a negative ferric chloride test, uric acid crystals in a 15-year-old boy's urine, and a requested Watson-Schwartz test?

Urinalysis Supervisor Actions in Special Situations

A. Suspected Tyrosyluria with Negative Ferric Chloride Test

When a negative ferric chloride test is reported for a patient suspected of having tyrosyluria, the supervisor should immediately repeat the test with a fresh specimen and verify proper testing technique before reporting the result to the physician.

The discrepancy between clinical suspicion and laboratory findings requires immediate investigation:

1. Repeat the ferric chloride test with proper technique using:

   • A fresh urine sample
   • Properly prepared reagents
   • Correct testing methodology

2. If the repeat test remains negative:

   • Document both test results
   • Notify the physician of the confirmed negative result
   • Suggest alternative testing methods for tyrosinemia such as:
     • Succinylacetone measurement (more specific for hepatorenal tyrosinemia) 1
     • Serum tyrosine levels

3. If the repeat test is positive:

   • Document the discrepancy
   • Investigate the cause of the initial false negative (reagent issues, technique problems, timing)
   • Implement corrective actions to prevent future errors
   • Report the positive result to the physician

Tyrosinemia with tyrosyluria is associated with liver cirrhosis and renal rickets, making accurate diagnosis critical for patient management 1.

B. Uric Acid Crystals in a 15-Year-Old Boy with Renal Calculi

The supervisor should confirm the finding with polarized microscopy, ensure proper pH measurement of the specimen, and recommend a 24-hour urine collection for comprehensive stone risk analysis to guide therapy for this patient with likely uric acid nephrolithiasis.

For this adolescent with recurrent renal calculi and uric acid crystals:

1. Immediate actions:

   • Confirm the presence of uric acid crystals using polarized microscopy
   • Measure urine pH (uric acid stones form primarily in acidic urine) 2
   • Document crystal morphology and quantity

2. Recommend to the physician:

   • 24-hour urine collection for comprehensive stone risk analysis including:
     • Urine volume
     • pH profile throughout the day
     • Uric acid excretion
     • Calcium, oxalate, citrate levels
     • Ammonium buffer capacity 2

3. Additional testing to consider:

   • Serum uric acid levels
   • Metabolic panel including electrolytes
   • Assessment for metabolic syndrome markers (as uric acid stone formers often have metabolic syndrome) 2

4. Management guidance:

   • Potassium citrate to alkalinize urine to a pH between 6-6.5
   • Liberal fluid intake
   • Dietary modifications 2

C. Watson-Schwartz Test Request

The Watson-Schwartz test is being requested to diagnose acute intermittent porphyria (AIP), specifically to detect porphobilinogen in urine which is the key diagnostic marker for this potentially life-threatening metabolic disorder.

The Watson-Schwartz test:

1. Purpose:

   • Qualitative screening test for urinary porphobilinogen (PBG)
   • Primary use is in the diagnosis of acute porphyrias, particularly acute intermittent porphyria

2. Clinical significance:

   • Elevated urinary PBG is the hallmark of acute porphyria attacks
   • Critical for diagnosing the cause of acute abdominal pain, neuropsychiatric symptoms, and autonomic dysfunction

3. Testing considerations:

   • Fresh urine specimen is required
   • Protect from light to prevent degradation of porphyrins
   • False positives can occur with certain medications
   • Positive results should be confirmed with quantitative testing

4. Supervisor actions:

   • Ensure laboratory staff are trained in proper test technique
   • Verify specimen collection and handling protocols
   • Confirm availability of necessary reagents
   • Consider recommending more specific quantitative tests if available

While this test has been largely replaced by more specific methods in many facilities, it remains valuable as a rapid screening tool when acute porphyria is suspected, allowing for prompt initiation of treatment in this potentially life-threatening condition.