From the Guidelines
Laboratory tests for evaluating fatigue should include a complete blood count (CBC) with differential, comprehensive metabolic panel, and endocrinologic evaluation, such as thyroid-stimulating hormone (TSH) levels, as recommended by the American Society of Clinical Oncology 1. When evaluating fatigue, it is essential to consider the presence of other symptoms, onset, and severity of fatigue to determine the appropriate laboratory tests.
- A CBC with differential can help identify anemia, infections, or other blood disorders that may be contributing to fatigue.
- A comprehensive metabolic panel can assess liver and kidney function, as well as electrolyte levels, to identify any underlying metabolic disorders.
- Endocrinologic evaluation, including TSH levels, can help diagnose thyroid disorders, such as hypothyroidism, which can cause fatigue. Additional tests may be ordered based on the patient's medical history, physical examination findings, and associated symptoms, such as iron studies, vitamin levels, and inflammatory markers. According to the European Society for Medical Oncology, laboratory tests should be considered as part of a diagnostic assessment to identify contributing and comorbid conditions that require treatment 1. It is crucial to note that the predictive values of laboratory tests are low in cancer-related fatigue, and a thorough clinical evaluation is necessary to establish the 'phenotype' of the individual patient's fatigue, which helps to tailor treatment or referral to an appropriately trained professional 1.
From the Research
Lab Tests for Fatigue
- The diagnosis of fatigue is typically guided by a comprehensive history and physical examination, including cardiopulmonary, neurologic, and skin examinations 2, 3.
- Laboratory studies may be used to identify underlying causes of fatigue, but results affect management in only 5 percent of patients 3.
- Common lab tests used to evaluate fatigue include:
- Complete Blood Count (CBC) to assess for anemia, inflammation, and other conditions 4.
- Serum ferritin to evaluate iron stores and potential iron deficiency anemia 5, 6.
- Thyroid function tests, such as Thyroid Stimulating Hormone (TSH), free T3, and free T4, to assess for hypothyroidism 5, 6.
- Anti-thyroid peroxidase (anti-TPO) antibody test to evaluate for autoimmune thyroiditis 5.