Confirming the presence of a myopathy associated with any 1 of the following disorders
-Exertional myoglobinuria in untrained individuals
-Myoglobinuria of progressive muscle disease
May suggest a myopathic cause for acute renal failure
**Urine Myoglobin Transport Tubes (T691) are kept in Main Marshfield Labs Specimen Processing. Contact Marshfield Labs Customer Service to order special tubes - 800-222-5835.**
1. Collect a preservative-free, random urine specimen.
2. If specimen is at ambient temperature, aliquot the urine to a urine myoglobin transport tube (T691) within 1 hour of collection. Refrigerate specimen.
3. If specimen is refrigerate, aliquot the urine to a urine myoglobin transport tube (T691) within 2 hours of collection.
Additional Information: Urinary myoglobin is highly unstable unless alkalinized with sodium carbonate preservative. Even with alkalinization, myoglobin deterioration is variable and specimen dependent (approximate averages of 10% at 1 day, 20% at 3 days, and 30% at 7 days).
Home collection of urine is not advised since urine must be transferred into Urine Myoglobin Transport Tube within 1-2 hours of collection, based on storage. Collection of urine should take place in clinic setting.
An elevated level of myoglobin in urine does not identify the clinical disorder.
Urine collected with acid as preservative will not be valid because acid interferes with analyte integrity.
Urinary myoglobin deteriorates rapidly unless stabilized immediately after collection by alkalizing with sodium carbonate.
Urinary myoglobin does not withstand freezing even when pH is raised with sodium carbonate.
Myoglobin is the oxygen-binding protein of striated muscle. Injury to skeletal or cardiac muscle results in the release of myoglobin. High concentrations appear very rapidly in the urine in various conditions including some metabolic diseases.
Conditions associated with myoglobinuria include:
Urine myoglobin increases with muscle necrosis, but the clinical consequences are variable. Therefore, myoglobin can confirm a clinical diagnosis of myopathy, but an elevated urine excretion of myoglobin is not specific for a clinical disorder.
In acute renal failure, an elevated urinary myoglobin can suggest a potential cause and, consequently, may indicate appropriate treatment courses.
< or =65 mcg/L for 18-83 years of age
Reference values have not been established for patients<18 or >83 years of age.
Increased excretion of urinary myoglobin is suggestive of 1 of the following disorders:
Most clinically significant elevations are elevated 2 to 10 times normal.
Visual pigmenturia occurs at myoglobin concentrations about 200 times normal (approximately 4000 mcg/L).
Renal toxicity depends on multiple factors such as renal perfusion and degree of acidity of urine.