What diagnostic tests should be done for a 17-year-old female with a year-long history of severe fatigue, orthostasis, and headaches?

Diagnostic Testing for a 17-Year-Old Female with Severe Fatigue, Orthostasis, and Headaches

A comprehensive orthostatic vital sign assessment with active standing test should be the first diagnostic test for this patient, followed by an ECG, complete blood count, comprehensive metabolic panel, and thyroid function tests to evaluate for Postural Orthostatic Tachycardia Syndrome (POTS) or other forms of orthostatic intolerance. 1

Initial Evaluation for Orthostatic Intolerance

The constellation of severe fatigue, orthostasis, and headaches in a 17-year-old female strongly suggests orthostatic intolerance, which requires specific testing:

• Active standing test: Measure heart rate and blood pressure while supine and then at 1,3, and 5 minutes after standing to assess for orthostatic hypotension or POTS 1
• For POTS diagnosis in adolescents (12-19 years): Look for heart rate increase ≥40 bpm within 10 minutes of standing without significant blood pressure drop 1
• Document associated symptoms during standing (lightheadedness, palpitations, tremor, weakness, visual disturbances) 1

Laboratory Testing

• Complete blood count: To evaluate for anemia or infection 1
• Comprehensive metabolic panel: To assess electrolytes, renal function, and glucose levels 1
• Thyroid function tests: To rule out thyroid dysfunction 1
• Iron studies (ferritin, iron, TIBC): To evaluate for iron deficiency 1
• Consider vitamin B12 and folate levels: To rule out deficiencies 1
• Morning cortisol: To assess adrenal function 1

Cardiovascular Assessment

• 12-lead ECG: To evaluate for cardiac conduction abnormalities 1
• Consider 24-hour Holter monitoring if symptoms suggest arrhythmia 1
• Consider echocardiogram to rule out structural heart disease if cardiac symptoms are prominent 1

Neurological Evaluation

• If headaches have orthostatic features (worsen when upright, improve when lying down), consider brain MRI to rule out intracranial hypotension 1, 2
• If headaches have migraine features or are severe, brain MRI may be indicated to rule out secondary causes 2, 3
• Consider tilt-table testing if the active standing test is inconclusive but symptoms strongly suggest orthostatic intolerance 1

Special Considerations for POTS

POTS is particularly common in young females and frequently presents with this exact symptom triad. Research shows:

• POTS is frequently associated with chronic fatigue syndrome, recent infections, and joint hypermobility syndrome 1
• Orthostatic headaches affect approximately two-thirds of POTS patients, especially those under age 30 4
• Almost all POTS patients (95.8% in one study) have comorbid migraine or probable migraine headaches 4

Autonomic Testing

• If initial evaluation suggests dysautonomia, consider referral for formal autonomic testing 1
• Autonomic reflex screen can help differentiate between various forms of orthostatic intolerance 1, 5

Medication Considerations

If POTS or orthostatic hypotension is confirmed:

• Consider a trial of midodrine, which increases standing systolic blood pressure by 15-30 mmHg at 1 hour after a 10 mg dose 6
• Fludrocortisone may be considered to enhance sodium retention and increase blood volume, but requires careful monitoring of blood pressure and electrolytes 7

Post-Infectious Considerations

• Given the prevalence of post-viral dysautonomia, consider testing for recent viral infections if symptoms began after an illness 8
• Post-COVID-19 dysautonomia can present with this exact symptom complex even after mild initial infection 8

Clinical Pitfalls to Avoid

• Don't dismiss orthostatic symptoms in adolescents as "just dehydration" or anxiety 1
• Orthostatic headaches can occur without detectable CSF leak, so normal brain imaging doesn't rule out orthostatic intolerance 5
• Delayed orthostatic hypotension may be missed if standing vital signs are only measured for 1-2 minutes 1