What blood work is recommended for patients suspected of having malignancy?

Blood Work for Suspected Malignancy

For patients suspected of having malignancy, a comprehensive diagnostic workup should include complete blood count with differential, comprehensive metabolic panel, lactate dehydrogenase, and specific tumor markers based on clinical presentation and suspected primary site.

Initial Laboratory Evaluation

Core Blood Tests for All Suspected Malignancies

• Complete Blood Count (CBC) with differential 1

  • Evaluates for cytopenias, leukocytosis, or abnormal cell populations
  • Particularly important for suspected hematologic malignancies

• Comprehensive Metabolic Panel 1

  • Includes:
    • Liver function tests (AST, ALT, alkaline phosphatase, bilirubin)
    • Renal function (BUN, creatinine)
    • Electrolytes (sodium, potassium, calcium, phosphorus)

• Lactate Dehydrogenase (LDH) 1

  • Elevated in many malignancies
  • Prognostic significance in lymphomas and other cancers

• Tumor Lysis Syndrome Panel 1

  • Particularly important for patients with large tumor burden
  • Includes uric acid, potassium, phosphorus, calcium

Site-Specific Tumor Markers

For Suspected Gynecologic Malignancy

• CA-125 1, 2
  • Primary test for suspected ovarian cancer
  • Should be ordered when peritoneal involvement is suspected

For Suspected Prostate Cancer

• Prostate-Specific Antigen (PSA) 1
  • Essential for males with suspected prostate cancer
  • Particularly useful in men with lower urinary tract symptoms

For Suspected Gastrointestinal Malignancy

• CEA, CA19-9, CA72-4 1
  • When GI primary is suspected

For Suspected Germ Cell Tumors

• Alpha-fetoprotein (AFP) 1
• Beta-human chorionic gonadotropin (β-hCG) 1
  • Particularly in males with suspected testicular cancer

For Suspected Neuroendocrine Tumors

• Chromogranin A 1

Tailoring Blood Work by Clinical Presentation

For Suspected Hematologic Malignancies

• More extensive CBC evaluation with peripheral blood smear 1
• Consider flow cytometry for suspected leukemia

For Suspected Occult Primary

• Comprehensive panel of tumor markers based on clinical presentation 1
• Blood tests should be guided by symptoms and suspected primary sites

Clinical Considerations and Pitfalls

Limitations of Blood Tests

• Blood tests alone rarely establish a definitive diagnosis of malignancy
• Normal blood work does not rule out malignancy 3
• The positive predictive value of abnormal CBC, LFTs, and other routine tests for occult metastasis is only about 1-1.5% 3

Patterns in Test Ordering

• Research shows that blood tests are more commonly ordered for patients with non-specific symptoms (e.g., fatigue, weight loss) than for those with alarm symptoms (e.g., breast lump) 4, 5
• Blood testing is associated with longer diagnostic intervals (median 49 vs 32 days) 5

When to Expand Testing

• Abnormal results on initial tests should prompt additional targeted testing
• Persistent symptoms despite normal initial tests warrant additional evaluation

Diagnostic Algorithm

1. Assess clinical presentation and suspected primary site
2. Order core blood tests (CBC with differential, comprehensive metabolic panel, LDH)
3. Add site-specific tumor markers based on clinical suspicion
4. Interpret results in clinical context
5. Proceed to appropriate imaging and/or tissue diagnosis as indicated by blood test results

Remember that blood tests are just one component of the diagnostic workup for suspected malignancy. Tissue diagnosis remains the gold standard for most cancers, and appropriate imaging studies should be ordered based on clinical presentation and laboratory findings.