Laboratory Testing for Suspected POTS
Order a 12-lead ECG, complete blood count, basic metabolic panel, and thyroid function tests as your initial laboratory workup for suspected POTS. 1, 2
Essential Baseline Laboratory Tests
Before attributing symptoms to POTS, you must exclude mimicking conditions through targeted laboratory testing:
- 12-lead ECG to rule out arrhythmias or conduction abnormalities that could explain tachycardia 1, 2
- Thyroid function tests to exclude hyperthyroidism, which commonly mimics POTS 1, 2
- Complete blood count (CBC) to evaluate for anemia, which can cause compensatory tachycardia 1
- Basic metabolic panel (BMP) to assess for electrolyte abnormalities and exclude dehydration 1
These four tests form the core laboratory evaluation and should be obtained in every patient before confirming POTS diagnosis. 1, 2
Expanded Laboratory Testing When POTS is Confirmed
Once you establish the POTS diagnosis through the 10-minute active stand test, consider additional testing based on clinical presentation:
Autoimmune and Inflammatory Markers
- Autoantibody testing should be considered in confirmed POTS cases, particularly when an autoimmune etiology is suspected 3, 2
- This is especially relevant in post-viral POTS or when symptoms suggest immune-mediated mechanisms 4, 5
Mast Cell Activation Syndrome (MCAS) Evaluation
If MCAS is suspected based on symptoms spanning multiple organ systems or allergy-like presentations:
- Obtain baseline serum tryptase level 3, 2
- Collect tryptase levels at baseline and 1-4 hours following symptom flares 3, 2
- A diagnostic increase requires 20% above baseline plus 2 ng/mL 3, 2
This testing should be reserved for patients with appropriate clinical history suggesting mast cell activation, not performed universally. 3
Additional Condition-Specific Testing
Consider these tests only when clinical presentation suggests specific comorbidities:
- Celiac disease serologies in patients with gastrointestinal symptoms, particularly those with joint hypermobility 3, 2
- Iron studies if hypovolemic POTS subtype is suspected, as iron deficiency contributes to this phenotype 6
- Beighton score assessment (clinical examination, not laboratory) for joint hypermobility syndrome screening 3, 2
What NOT to Order Routinely
Avoid reflexive ordering of extensive autonomic panels or specialized testing in straightforward cases:
- Comprehensive autonomic function testing (beat-to-beat BP monitoring, Valsalva maneuver, sudomotor testing) should be reserved for atypical presentations or when diagnosis remains uncertain after initial evaluation 3, 1, 2
- Mast cell staining on endoscopic biopsies lacks validated clinical utility for isolated GI symptoms without evidence of generalized mast cell disorder 3
- Extensive food allergy panels are not supported by evidence in POTS evaluation 3
Critical Testing Conditions
Laboratory tests should be obtained under proper conditions to ensure accuracy:
- Patient should be fasted for 3 hours before testing 1, 2
- Avoid nicotine, caffeine, theine, or taurine-containing drinks on the day of examination 1, 2
- Perform testing in a quiet environment at 21-23°C, preferably before noon 1, 2
Common Pitfalls to Avoid
- Failing to exclude hyperthyroidism before diagnosing POTS leads to misdiagnosis, as thyroid dysfunction is a common and treatable cause of orthostatic tachycardia 1, 2
- Not screening for anemia misses a reversible cause of compensatory tachycardia 1
- Ordering extensive autoimmune panels without clinical indication wastes resources and may lead to false-positive results that confuse management 3
- Universal MCAS testing in all POTS patients is not evidence-based; reserve tryptase testing for those with multisystem symptoms suggesting mast cell activation 3, 2
Medication Review as Part of Evaluation
While not a laboratory test, a comprehensive medication review is mandatory, particularly examining cardioactive drugs, diuretics, vasodilators, and negative chronotropes that could cause or exacerbate orthostatic symptoms. 3, 2