What are the standard cutoff points for aldolase (alanine phosphate) levels?

Standard Cutoff Points for Aldolase

The standard cutoff for aldolase is 6 times the upper limit of normal (ULN) in the context of myositis assessment, as established by the American College of Rheumatology/European League Against Rheumatism criteria for dermatomyositis and polymyositis. 1

Context-Specific Cutoff Values

For Myositis (Dermatomyositis/Polymyositis)

• The enzyme range for aldolase is 6× ULN when calculating improvement scores in adult dermatomyositis/polymyositis 1
• The enzyme range for aldolase is 6× ULN when calculating improvement scores in juvenile dermatomyositis 1
• This cutoff is used to calculate the 90% range of enzymes from natural history data and represents the expected maximum elevation in these inflammatory muscle diseases 1

Laboratory Reference Ranges

• Normal serum aldolase levels in healthy subjects are approximately 171 ± 39 ng/ml (mean ± 2 SD) 2
• Upper limit of normal is typically around 210 ng/ml based on radioimmunoassay studies 2
• The specific ULN varies by individual laboratory due to differences in assay methods and reference populations 1

Clinical Interpretation Framework

When Aldolase is Elevated with Normal CK

• Aldolase elevation with normal creatine kinase strongly predicts myopathy with perimysial pathology (92% of cases) 3
• This pattern is associated with muscle discomfort (92%), weakness (50%), joint pain (75%), skin disorders (75%), and pulmonary involvement (50%) 3
• Aldolase should be measured in all patients suspected of having eosinophilic fasciitis, as it is more consistently abnormal than peripheral eosinophilia or ESR 4

Disease-Specific Patterns

• In acute hepatitis, aldolase B isoenzyme rises to very high levels, while it is only slightly elevated in cirrhosis, chronic hepatitis, and obstructive jaundice 5
• In fulminant hepatitis, serum aldolase A levels increase remarkably 2
• In liver cell carcinoma, 32 of 34 patients (94%) showed clearly increased serum aldolase A levels (>210 ng/ml), making it more sensitive than alpha-fetoprotein 2
• In myocardial infarction, aldolase rises within 24-48 hours and returns to normal within 5 days 5

Important Clinical Caveats

Muscle Disease Assessment

• When monitoring treatment response in myositis, the most abnormal enzyme at baseline should be tracked (among creatine kinase, aldolase, LDH, AST, and ALT) 1
• The 6× ULN cutoff represents the upper boundary of the expected range for calculating percentage changes in disease activity 1

Isoenzyme Considerations

• Aldolase A predominates in skeletal muscle, myocardium, and malignant tumors 5, 2
• Aldolase B is the predominant isoenzyme in liver disease 5
• Erythrocytes are rich in aldolase, so hemolytic anemia can cause elevations 5

Laboratory Variability

• Always use the ULN specific to your laboratory when interpreting results, as methods and reference populations vary 1
• In nonmalignant liver diseases, aldolase A levels typically remain <210 ng/ml 2