From the Guidelines
Initial laboratory tests recommended for patients presenting with fatigue include a complete blood count (CBC), comprehensive metabolic panel (CMP), and thyroid-stimulating hormone (TSH) as per the American Society of Clinical Oncology clinical practice guideline adaptation 1. These tests help identify common causes of fatigue such as anemia, electrolyte abnormalities, kidney or liver dysfunction, and thyroid disorders. The testing approach should be guided by the patient's history, physical examination findings, and risk factors rather than ordering extensive panels indiscriminately. Key points to consider when ordering laboratory tests for fatigue include:
- Considering the presence of other symptoms, onset, and severity of fatigue when deciding which tests to order 1
- Using a CBC with differential to compare end-of-treatment hemoglobin/hematocrit with current values and assess other cell lines (WBC and platelets) 1
- Ordering a comprehensive metabolic panel to assess electrolytes, hepatic and renal function 1
- Performing an endocrinologic evaluation, including TSH, and considering more comprehensive evaluation or referral to specialist if other symptoms are present 1 If initial testing is unrevealing but symptoms persist, a second round of more targeted testing based on clinical suspicion may be warranted.
From the Research
Initial Laboratory Tests for Fatigue
The following laboratory tests are recommended for patients presenting with fatigue:
- Complete Blood Count (CBC) with differential 2, 3
- Comprehensive Metabolic Panel (CMP) 4
- Measurement of inflammatory markers and autoantibodies 4
- Iron panel (ie, ferritin and iron levels, total iron-binding capacity, transferrin saturation) 3
- Levels of vitamin B12 and folate 3
- Reticulocyte count 5, 3
- Peripheral blood smear 3
Rationale for Laboratory Tests
These laboratory tests can help identify underlying causes of fatigue, such as:
- Anemia 5, 3
- Autoimmune diseases 4
- Cardiovascular and metabolic diseases 2
- Nutritional deficiencies (e.g., vitamin B12, iron) 3
Approach to Laboratory Testing
The approach to laboratory testing for fatigue should be logical and focused on identifying the underlying cause of the symptom 5, 6. A thorough history and physical examination should be performed before ordering laboratory tests 3, 6.