From the Guidelines
A lethargy workup should begin with a comprehensive history and physical examination to identify potential causes, as this approach is crucial in determining the underlying etiology and guiding further management 1. The initial evaluation should include a focused history, assessing the patient's current disease status, treatment, and response to treatment, as well as a review of systems to determine the various organ systems affected 1. A thorough physical examination should also be performed, including vital signs, a general physical exam, and a neurologic exam, such as the National Institutes of Health Stroke Scale (NIHSS) or Glasgow Coma Score (GCS) if neurological symptoms are present 1. Initial laboratory tests should include:
- Complete blood count
- Comprehensive metabolic panel
- Thyroid function tests
- Urinalysis
- Blood glucose measurement Additional testing may include:
- Inflammatory markers (ESR, CRP)
- Vitamin levels (B12, D)
- Infectious disease screening
- Toxicology screening If neurological symptoms are present, brain imaging (CT or MRI) and possibly lumbar puncture should be considered 1. For persistent unexplained lethargy, sleep studies may be warranted to evaluate for sleep disorders 1. Cardiac evaluation with ECG and possibly echocardiogram may be necessary if cardiovascular causes are suspected 1. The workup should be tailored to the patient's specific symptoms, age, and medical history, as lethargy can result from numerous conditions, including infections, metabolic disorders, endocrine abnormalities, neurological conditions, medication side effects, substance use, or psychological disorders like depression 1.
From the Research
Diagnostic Approach for Lethargy
The diagnostic approach for lethargy involves a thorough history and complete physical examination, in conjunction with some screening laboratory tests, to rule out most medical causes of fatigue 2.
Initial Evaluation
- A thorough history and physical examination can help identify the cause of lethargy in most cases 2.
- Screening laboratory tests, such as a complete blood count, can aid in the diagnosis of underlying medical conditions 3.
Differential Diagnosis
- Medical illnesses, such as anemia or infection, can cause lethargy and should be suspected based on history and physical examination 2.
- Psychiatric illnesses, such as depression or anxiety, can also cause lethargy and should be considered in the differential diagnosis 2.
- Sudden unresponsiveness with normal vital signs can have a range of causes, including primary brain diseases or nonstructural systemic conditions, and should trigger immediate and focused diagnostic evaluation 4.
Laboratory Tests
- A complete blood count can help diagnose underlying hematologic disorders or other medical problems 3.
- Other laboratory tests, such as electrolyte panels or liver function tests, may be ordered based on the patient's history and physical examination.