Laboratory Workup for Fatigue, Bloating, Anxiety, and Depression
Order a comprehensive metabolic panel (CMP), complete blood count (CBC), thyroid-stimulating hormone (TSH), and consider inflammatory markers (CRP, ESR) to identify treatable medical causes of these symptoms, as medical conditions must be ruled out before attributing symptoms solely to psychiatric disorders.
Essential Laboratory Tests
The guideline evidence emphasizes that medical or substance-induced causes of depressive symptoms and fatigue must be determined and treated first 1, 2. This approach prioritizes identifying reversible organic causes that directly impact morbidity and quality of life.
Core Laboratory Panel
Complete Blood Count (CBC): Screen for anemia (a common contributor to fatigue), infection, and hematologic abnormalities 2, 3
Comprehensive Metabolic Panel (CMP): Evaluate for electrolyte imbalances, renal dysfunction, hepatic dysfunction, and glucose abnormalities 1, 2
Thyroid Function (TSH, free T4): Essential to exclude thyroid disease as a reversible cause of fatigue, depression, and anxiety 2, 5
Additional Targeted Tests Based on Clinical Context
Inflammatory markers (CRP, ESR): Consider when systemic inflammation is suspected, as inflammation correlates with fatigue severity and poor quality of life 3
- The modified Glasgow prognostic score (mGPS), which incorporates CRP and albumin, shows significant association with fatigue 3
Lipid panel: Triglyceride levels may have predictive value for depression, particularly in patients with metabolic concerns 4
Vitamin B12 and folate: Screen if nutritional deficiency is suspected based on dietary history or gastrointestinal symptoms
Vitamin D: Consider in patients with limited sun exposure or risk factors for deficiency
Clinical Assessment Framework
While laboratory tests are important, the diagnostic assessment should involve a focused history, thorough medical examination, review of body systems, and mental status examination 2. The guidelines specifically recommend:
- Screen for depression using PHQ-9 as the primary tool 1, 5
- Screen for anxiety using GAD-7 1
- Evaluate sleep quality as it correlates significantly with both fatigue and mood symptoms 3
Two-Question Depression Screen
For rapid screening in busy clinical settings 2:
- "In the last month, have you often felt dejected, sad, depressed or hopeless?"
- "In the last month, did you experience significantly less pleasure than usual with the things you normally like to do?"
Important Caveats
Predictive values of laboratory tests are low for cancer-related fatigue and mood disorders 2, meaning normal labs don't exclude these conditions. However, abnormal results identify treatable contributing factors that improve outcomes when addressed.
The bloating component suggests potential gastrointestinal pathology. Research shows 84% of patients with gastrointestinal disorders demonstrate state anxiety, and 27% show current depression 6. Consider:
- Celiac serology (tissue transglutaminase IgA with total IgA) if celiac disease is suspected
- H. pylori testing if dyspepsia is prominent (associated with both anxiety and depression) 6
Do not order extensive autoimmune panels, Lyme titers, or other esoteric tests without specific clinical indicators, as this leads to false positives and unnecessary patient anxiety without improving outcomes.
Follow-Up Strategy
After obtaining initial labs, follow up is mandatory after treatment for fatigue or any identified secondary cause 7. If moderate-to-severe symptoms persist despite treating identified medical causes, referral to psychiatry or psychology is necessary for further diagnostic assessment 1.