Aldolase is an enzyme found inside body cells. A blood test measures the concentration of aldolase circulating in the bloodstream to help diagnose or monitor certain health conditions. Since aldolase is normally contained within cells, high amounts in the blood typically suggest cellular damage has occurred, causing the enzyme to leak out. Aldolase is most concentrated in muscle tissue and the liver, so elevated levels usually indicate injury in one of these two organ systems.
The Enzyme’s Function in the Body
Aldolase, specifically the Aldolase A isoform, performs a core function in glycolysis, the process of converting sugar into usable energy within the cell. It catalyzes a reversible reaction, breaking down the six-carbon sugar fructose 1,6-bisphosphate into two three-carbon molecules. This action is necessary for the cell to generate adenosine triphosphate (ATP), the body’s primary energy currency. Aldolase is highly concentrated in cells with high energy demands, such as skeletal muscle, red blood cells, and liver cells.
The enzyme is confined within the cell membrane, which acts as a barrier to the bloodstream. When muscle or liver cells sustain injury, this membrane is compromised, allowing the internal contents, including aldolase, to spill out into the serum. The amount of aldolase in a blood sample reflects the extent of this cellular leakage or damage. Although different types of aldolase exist, the standard blood test measures total aldolase activity.
Preparing for the Blood Test and Normal Ranges
A physician may order an aldolase test if a patient reports unexplained muscle weakness or pain, or if a muscle disease like muscular dystrophy or an inflammatory myopathy is suspected. The test is also used to monitor the progression of a known muscle disease or to check treatment effectiveness. Since aldolase is present in the liver, the test may be included in a broader panel when liver damage is suspected.
Preparation requires specific compliance to ensure accurate results. Patients are often instructed to fast (not eating or drinking anything other than water) for six to twelve hours before the blood draw. Avoiding strenuous physical exercise for at least twelve hours prior is also recommended, as intense activity can temporarily damage muscle fibers and falsely elevate the enzyme level. The procedure involves a simple blood draw, usually from a vein in the arm.
Interpreting the results requires comparing the patient’s measurement to established “Normal Ranges.” For adults, the typical normal range is approximately 1.0 to 7.5 units per liter, though this varies slightly between laboratories. Children and newborns naturally have higher aldolase levels due to greater muscle mass development and metabolic rates. A physician must interpret the results within the context of the patient’s overall health and symptoms, accounting for individual factors like age and muscle mass.
Clinical Significance of Elevated Levels
Higher than normal aldolase levels strongly indicate tissue damage, most frequently involving skeletal muscle. The test is commonly used in diagnosing and monitoring inflammatory myopathies, such as dermatomyositis and polymyositis. In these conditions, the immune system attacks muscle tissue, and the resulting destruction causes a significant release of aldolase into the blood.
Aldolase levels are also highly elevated in muscular dystrophies, like Duchenne muscular dystrophy, characterized by progressive muscle breakdown. Aldolase is often measured alongside creatine kinase (CK), another muscle enzyme, to confirm the source of the injury. Aldolase can be a valuable diagnostic marker because in some inflammatory muscle diseases, it may be elevated even when CK levels remain normal.
The liver is the other major source of aldolase, specifically the Aldolase B isoform, so elevated levels can point toward hepatic conditions. Acute viral hepatitis, which causes inflammation and destruction of liver cells, leads to a rise in circulating aldolase. Other liver issues like cirrhosis or obstructive jaundice may also cause mild elevations of the enzyme.
Beyond muscle and liver disease, significant tissue trauma, such as a heart attack (myocardial infarction), can cause a temporary rise in aldolase levels, peaking within a day or two. Certain types of cancer have also been associated with elevated aldolase activity. These include liver, pancreatic, and prostate cancer, although the test is not typically used for primary screening.
Potential Non-Disease Influences and Follow-Up Actions
Several factors unrelated to disease can temporarily influence aldolase levels. Strenuous exercise, especially resistance training or intense endurance activity performed shortly before the blood draw, can cause temporary micro-trauma to muscle fibers, leading to a transient elevation. Certain medications, including statins and steroids, can also affect aldolase levels due to their potential impact on muscle tissue.
If a patient receives an abnormal result, the physician typically orders follow-up tests to pinpoint the source of the elevation. Aldolase is rarely interpreted alone; instead, it is compared with other enzymes. These include creatine kinase (CK) to confirm muscle injury, or alanine aminotransferase (ALT) and aspartate aminotransferase (AST) to evaluate the liver. This contextual analysis helps the physician differentiate between muscle and liver damage before proceeding with further diagnostic imaging or biopsies.