From the Guidelines
Laboratory tests for syncope should be selective and guided by the patient's history, physical examination, and initial evaluation findings, with a focus on identifying the underlying cause of syncope to improve morbidity, mortality, and quality of life outcomes. The most recent and highest quality study, 1, published in 2021, emphasizes the importance of a detailed history and physical examination in assessing patients with syncope, and recommends against routine extensive laboratory testing.
Key Laboratory Tests
- Basic tests include:
- Complete blood count to assess for anemia
- Electrolyte panel to identify imbalances like hyponatremia or hypokalemia
- Blood glucose measurement to rule out hypoglycemia
- Cardiac biomarkers such as troponin if cardiac ischemia is suspected
- A 12-lead ECG is essential to detect arrhythmias, conduction abnormalities, or signs of structural heart disease
- Additional tests may include:
- Thyroid function tests if thyroid dysfunction is suspected
- Drug screens if medication-related syncope is possible
- Pregnancy tests for women of childbearing age
Specialized Tests
More specialized tests like echocardiography, tilt-table testing, or prolonged cardiac monitoring should be reserved for cases where initial evaluation suggests specific etiologies, as recommended by 1 and 1. These tests help identify the underlying cause of syncope, which is crucial for appropriate management and improving patient outcomes.
Avoiding Unnecessary Testing
Routine extensive laboratory testing for all syncope patients is not cost-effective and rarely yields diagnostic information beyond what a careful history and physical examination provide, as noted in 1 and 1. Therefore, it is essential to prioritize selective testing based on the patient's clinical presentation and initial evaluation findings to minimize unnecessary testing and improve patient outcomes.
From the Research
Lab Tests for Syncope
- The diagnosis of syncope is primarily based on a thorough history and physical examination, including orthostatic assessment 2.
- Short-term risk assessment is crucial in determining the need for admission or outpatient evaluation 2.
- For patients with suspected cardiac syncope, monitoring is indicated until a diagnosis is made 2.
- In cases of suspected reflex syncope or orthostatic hypotension, outpatient evaluation with tilt-table testing is recommended 2.
- The use of syncope units has been shown to improve the rate of diagnosis while reducing costs, making them a highly recommended approach 2.