Does Sertraline Cause False-Positive Plasma Free Fractionated Metanephrines?
No, sertraline does not cause false-positive plasma free fractionated metanephrine assays. The FDA drug label for sertraline specifically mentions false-positive urine immunoassay screening tests for benzodiazepines, but makes no mention of interference with metanephrine testing 1. The Endocrine Society guidelines identify medications that interfere with metanephrine measurements—specifically noting tricyclic antidepressants and drugs that directly interfere with measurement methods—but do not list selective serotonin reuptake inhibitors (SSRIs) like sertraline as problematic 2.
Key Evidence Supporting This Conclusion
Drug Class Distinctions Matter
The most recent and highest-quality research (2024) demonstrates that norepinephrine reuptake blockers (tricyclic antidepressants and serotonin-norepinephrine reuptake inhibitors) cause false-positive elevations in plasma normetanephrine and methoxytyramine, with false-positive rates rising from 4.8% to 23.0% for normetanephrine 3. Critically, this same study found that selective serotonin reuptake inhibitors did not increase plasma concentrations of metabolites 3.
Sertraline is a selective serotonin reuptake inhibitor (SSRI), not a norepinephrine reuptake blocker. This pharmacologic distinction is essential—sertraline's mechanism does not interfere with catecholamine disposition in the way that tricyclic antidepressants do.
Guideline-Based Medication Concerns
The Endocrine Society guidelines explicitly state that medications interfering with catecholamine disposition (specifically mentioning tricyclic antidepressants) can result in raised biochemical test results 2. The absence of SSRIs from this list, combined with their specific mention of tricyclics, indicates that SSRIs like sertraline are not recognized as problematic.
Clinical Implications
- Continue sertraline during metanephrine testing: There is no need to discontinue sertraline before plasma free metanephrine testing
- If elevated results occur: Follow standard protocols for borderline elevations, including repeat sampling in the supine position after 30 minutes of recumbency 2
- Consider other causes: If metanephrines are elevated in a patient on sertraline, investigate other medications (particularly tricyclic antidepressants, SNRIs, α-blockers, or antipsychotics), improper sampling technique (seated vs. supine position), physiological stress, or actual pheochromocytoma/paraganglioma 3, 4, 5
Important Caveats
While sertraline itself does not cause false positives, be aware that:
- Sampling position matters critically: Seated sampling increases false-positive rates regardless of medications 2
- Other antidepressants do interfere: If a patient is on combination therapy including tricyclics or SNRIs (venlafaxine, duloxetine), these can cause false elevations 3
- Urinary vs. plasma testing: The evidence specifically addresses plasma metanephrines; urinary metanephrines may have different interference patterns 4, 5