Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1274 page)

Decreased In

   Wilson disease

   Fanconi syndrome

   Some malignancies

   Low-purine diet

   Folic acid deficiency

   Limitations

   Hyperuricosuria is present in patients with renal calculus formation. Even mild renal failure decreases uric acid excretion. Uric acid excretion is decreased with hypertension.

   Urine uric acid levels are elevated in states of uric acid overproduction such as in leukemia and polycythemia and after intake of food rich in nucleoproteins.

   High levels of bilirubin and ascorbic acid may interfere with measurement.

   Rasburicase (Elitek) causes enzymatic degradation of uric acid within blood samples left at room temperature resulting in spuriously low uric acid levels. To ensure accurate measurements in patients who have received rasburicase, blood must be collected into prechilled tubes containing heparin anticoagulant and immediately immersed and maintained in an ice bath; plasma samples must be assayed within 4 hours of sample collection.

URINALYSIS, COMPLETE

   Definition

   The dipstick reagent strip method is commonly used to assess the chemical evaluation of urine. The most frequently performed chemical tests using reagent test strips are specific gravity, pH, protein, glucose, ketones, blood, leukocyte esterase, nitrite, bilirubin, and urobilinogen.

   
Specific gravity:
Specific gravity is a measure of the dissolved substances present in the urine. It is a physical property of urine and an expression of concentration.