26298 Myoglobin, Random, Urine (MYGLU)

​​Myoglobin, Urine

U MYGLUSO

​Confirming the presence of a myopathy 

**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.**

Collection Instructions:

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 at refrigerate temperature, 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. 

Home collection of urine is not advised since urine must be transferred into Urine Myoglobin Transport Tube within 1-2 hou​rs of collection, based on storage.  Collection of urine should take place in clinic setting.   

An elevated level of urinary myoglobin alone does not identify the clinical disorder.

Physiological variables, such as patient hydration status, acid-base status, kidney function, and hypoxia affect myoglobin metabolism and, consequently, its presence in urine.

Urinary myoglobin concentration deteriorates rapidly unless stabilized immediately after collection by alkalinizing with sodium carbonate. Urine collected with any preservative other than sodium carbonate will not provide valid results.

Urinary myoglobin does not withstand freezing even when the pH is raised with sodium carbonate.​

Myoglobin is a small 17.8 kDa oxygen-binding heme protein, present in striated muscle to carry and store oxygen in muscle cells. By virtue of its small size, myoglobin is readily filtered by the glomerulus and catabolized by endocytosis and proteolysis in the proximal tubule. Healthy subjects normally have low concentrations (less than 5%) of protein appearing in the urine. Injury to skeletal or cardiac muscle results in a large release of myoglobin into systemic circulation within a few hours, which can overwhelm tubular resorption causing notable quantities of myoglobin to appear in urine giving it a red-brown appearance. The presence of myoglobin in the urine is a risk factor for developing acute kidney injury. Myoglobin concentration declines rapidly, with a serum half-life of 2 to 3 hours and has been studied for its ability to predict acute kidney injury.

High concentrations appear very rapidly in the urine in various conditions, including some metabolic diseases.

Conditions that can lead to rhabdomyolysis associated with myoglobinuria include:

-Trauma or crush injury

-Heatstroke, hypothermia, malignant hyperthermia

-Seizures, strenuous exercise, prolonged immobility

-Hypoxic injury

-Metabolic disturbances in electrolyte concentrations

-Genetic disorders that lead to muscle cell breakdown

-Infections

-Drugs or toxins

The presence of myoglobin in the urine can indicate serious muscle injury, which is a risk factor for developing acute kidney injury. Rhabdomyolysis is often confirmed and monitored by measuring serum creatine kinase, electrolytes, kidney function, and urine tests for protein and blood. Myoglobin will give a positive reaction with hemoglobin test strips, though red blood cells will be absent upon microscopic review.

0-24 mcg/L 

Reference values have not been established for patients younger than 18 years; however myoglobin is not expected to be detectable in urine.

Increased excretion of urinary myoglobin is suggestive of one of the disorders or conditions listed in Test Information.

Most clinically significant elevations are elevated 2 to 10 times normal.