What is the significance of elevated aldolase levels in patients with influenza (flu) and how is it managed?

Aldolase and Influenza: Clinical Significance and Management

Direct Answer

Elevated aldolase levels are not a typical or clinically significant finding in uncomplicated influenza infections, and routine aldolase testing is not recommended in the management of flu patients. 1, 2

When Aldolase Testing Is Relevant in Influenza Context

Aldolase elevation in influenza patients should prompt evaluation for specific complications rather than being considered a direct manifestation of the viral infection itself:

Myositis/Rhabdomyolysis

• Creatine kinase (CK) should be measured if myositis is suspected in patients presenting with severe myalgia, muscle weakness, or clinical concern for muscle inflammation 1
• Aldolase A is expressed in muscle tissue and becomes elevated in myotonic muscular diseases, polymyositis, and muscle injury 3
• In the context of immune checkpoint inhibitor-related myositis (a relevant differential), both CK and aldolase are monitored together, with aldolase potentially elevated even when CK is normal in early regenerating muscle cells 1, 4
• If influenza patients develop severe myalgia with suspected myositis, check CK first; aldolase adds limited additional value 1

Hepatic Involvement

• Aldolase B isozyme rises to very high levels in acute hepatitis, though liver function tests (transaminases) are the primary screening tools 3
• Liver function tests should be obtained in hospitalized influenza patients, as transaminases are elevated in 27% of influenza A cases 1, 5
• Aldolase is not part of routine hepatic assessment in influenza; standard liver enzymes (AST, ALT) are sufficient 1

Recommended Laboratory Workup for Hospitalized Influenza Patients

The evidence-based approach does not include routine aldolase testing 1, 2:

Standard blood tests for admitted patients:

• Full blood count (leucocytosis with left shift may occur; lymphopenia noted in severe cases) 1, 5
• Urea, creatinine, and electrolytes (assess for renal impairment and guide fluid management) 1, 5
• Liver function tests (transaminases elevated in 27% of influenza A patients) 1, 5
• Creatine kinase only if myositis is suspected (not routine) 1
• C-reactive protein may aid in diagnosing suspected secondary bacterial infection 1

Clinical Context: Aldolase as a Biomarker

Understanding aldolase biology clarifies why it's not routinely measured in influenza:

• Aldolase A is predominantly found in muscle tissue and is highest in undifferentiated and early regenerating muscle cells 4
• Isolated aldolase elevation (without CK elevation) reflects damage to early regenerating muscle cells, which is not a typical pattern in viral influenza 4
• Aldolase lacks specificity for influenza-related complications compared to more targeted markers 3

Management Algorithm When Muscle Symptoms Are Present

If a flu patient presents with severe myalgia or suspected myositis:

1. Check CK level first (primary marker for muscle injury) 1
2. Assess for rhabdomyolysis with urinalysis 1
3. Monitor renal function (urea, creatinine) 1, 5
4. Aldolase may be considered if CK is normal but clinical suspicion for muscle pathology remains high, though this is uncommon in typical influenza 1, 4

Key Clinical Pitfall

Do not routinely order aldolase in influenza patients. The standard laboratory workup outlined in multiple influenza management guidelines does not include aldolase testing 1, 2, 5. If muscle complications are suspected, CK is the appropriate first-line test, with aldolase reserved for specific scenarios where early muscle regeneration patterns need assessment (typically in autoimmune myositis contexts, not viral infections) 1, 4.