Phys · general-medicine
Undifferentiated Fatigue — A Systematic Diagnostic Approach
Also known as fatigue · tiredness · chronic fatigue · lassitude · malaise · lethargy · asthenia · lack of energy · low energy · excessive daytime sleepiness · undiagnosed fatigue · unexplained fatigue · post-viral fatigue · post-exertional malaise · myalgic encephalomyelitis · ME · CFS · ME/CFS · chronic fatigue syndrome · systemic exertion intolerance disease · long COVID · post-COVID condition · depression screen · PHQ-2 · iron deficiency fatigue · Addison disease · narcolepsy · obstructive sleep apnoea · STOP-Bang
Consultant-physician-depth guide to the diagnostic approach to the patient with chronic fatigue. Covers the three functional categories (physiological — sleep deprivation, overwork, deconditioning, pregnancy, post-viral; psychological — depression, anxiety, chronic stress, burnout, grief; physical or systemic — anaemia, thyroid disease, diabetes, cardiac failure, sleep apnoea, CKD, hepatic failure, COPD, malignancy, autoimmune disease, chronic infection, drug-related, nutritional, Addison disease, narcolepsy, myasthenia gravis), the focused history with the PHQ-2 and GAD-2 mood screens, the systematic examination with the bedside discriminators (pallor, koilonychia, clubbing, hyperpigmentation, the postural blood pressure, the thyroid), the two-tier investigation framework (Tier 1 — FBC, ferritin, B12, folate, U and E, LFTs, TFTs, CRP, glucose and HbA1c, vitamin D, urinalysis, CXR, ECG, pregnancy test; Tier 2 — autoimmune screen, HIV and hepatitis serology, troponin and BNP, sleep study, short Synacthen), the principle of avoiding over-investigation, the management of the cause and of the unexplained fatigue (reassurance, sleep hygiene, graded activity, CBT, medication review, depression treatment, planned review), and the specific guidance on ME and CFS (NICE 2021 NG206 — the withdrawal of graded exercise therapy, the pacing and energy management) and post-COVID condition (long COVID). Structured for FRACP DWE and DCE, MRCP and ABIM.
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Target exams
Red flags
- Unintentional weight loss of more than 5 per cent in 6 months in a fatigued patient is malignancy or chronic infection until proven otherwise — escalate to CT imaging, a myeloma screen and the targeted endoscopy
- Fatigue with a postural blood pressure drop, hyperpigmentation of the palmar creases or buccal mucosa, hyponatraemia with hyperkalaemia and weight loss is primary adrenal insufficiency (Addison disease) until the short Synacthen test is normal — a missed diagnosis is a missed adrenal crisis
- New fatigue with progressive anaemia, night sweats, fever or lymphadenopathy is a haematological malignancy (lymphoma, myeloma, leukaemia) until the full blood count, the film, the lactate dehydrogenase and the myeloma screen are reviewed
- Fatigue with fatigable ptosis or diplopia that worsens with sustained activity and improves with rest is myasthenia gravis until the acetylcholine receptor antibodies and the single-fibre EMG are reviewed — a missed diagnosis risks a myasthenic crisis
- Fatigue with post-exertional malaise (a worsening 12 to 72 hours after exertion with a slow recovery) is myalgic encephalomyelitis or chronic fatigue syndrome or post-COVID condition — do NOT prescribe graded exercise therapy; the 2021 NICE NG206 guideline withdrew it because of the risk of harm
- Daytime sleepiness with loud snoring, witnessed apnoea and obesity in a middle-aged patient is obstructive sleep apnoea — use the STOP-Bang score and a polysomnogram, because the untreated disease carries a high cardiovascular risk
Undifferentiated Fatigue — A Systematic Diagnostic Approach
The answer first
Fatigue is a symptom common to the physiological, the psychological and the systemic — which is exactly why a structured framework beats chasing a single guess. Use a three-category frame (physiological, psychological, physical or systemic), take a history that includes the mood screen, examine for the bedside discriminators, and let the Tier 1 screen narrow the differential.[1]
The reproducible sequence for any fatigued patient:[1]
- Establish the duration and impact. Acute or subacute (days to weeks) suggests an organic cause — infection, anaemia, a new endocrine or cardiac presentation. Chronic (more than 6 weeks) is where the three-category framework earns its place.
- Take the focused history with the mood screen. The PHQ-2 and GAD-2 are the validated screens; a positive score prompts the formal mood assessment. Ask about weight loss, night sweats, fever, sleep quality and medications.
- Examine for the systemic discriminators. Pallor and koilonychia of iron deficiency, hyperpigmentation and postural drop of Addison disease, the goitre of thyroid disease, the gallop of heart failure, the proximal weakness of a myopathy, the fatigable ptosis of myasthenia gravis.
- Order the Tier 1 screen together and interpret it together. FBC, ferritin, B12 and folate, U and E, LFTs, TFTs, CRP, glucose and HbA1c, vitamin D, urinalysis, chest X-ray and ECG — plus a pregnancy test in women of reproductive age.
- Treat the cause if one is found. If the Tier 1 is normal and there are no red flags, the management is reassurance, lifestyle intervention, medication review, depression treatment and planned review — not a blanket Tier 2 panel.[1]
References7ShowHide
- [1]Kroenke K, Spitzer RL, Williams JB The Patient Health Questionnaire-2: validity of a two-item depression screener Med Care, 2003.PMID 14583691
- [2]Verdon F, Burnand B, Stubi CLF, et al. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial BMJ, 2003.PMID 12763985
- [3]Krayenbuehl PA, Battegay E, Breymann C, et al. Intravenous iron for the treatment of fatigue in nonanemic, premenopausal women with low serum ferritin concentration Blood, 2011.PMID 21705493
- [4]Bateman L, Bested AC, Bonilla HF, et al. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Essentials of Diagnosis and Management Mayo Clin Proc, 2021.PMID 34454716
- [5]Nagappa M, Liao P, Wong J, Auckley D, Ramachandran SK, Memtsoudis S, Mokhlesi B, Chung F Validation of the STOP-Bang Questionnaire as a Screening Tool for Obstructive Sleep Apnea among Different Populations: A Systematic Review and Meta-Analysis PLoS One, 2015.PMID 26658438
- [6]Bornstein SR, Allolio B, Arlt W, et al. Diagnosis and Treatment of Primary Adrenal Insufficiency: An Endocrine Society Clinical Practice Guideline J Clin Endocrinol Metab, 2016.PMID 26760044
- [7]Ceban F, Ling S, Lui LMW, et al. Fatigue and cognitive impairment in Post-COVID-19 Syndrome: A systematic review and meta-analysis Brain Behav Immun, 2022.PMID 34973396