Plasma/serum 5-hydroxytryptophan concentration

Method

5-hydroxytryptophan concentration in serum or platelet-poor plasma by chromatographic assay (HPLC with electrochemical detection, or LC-MS/MS). Where pharmacokinetic modelling is reported, the compartmental model and the derived apparent clearance are recorded on the edge.

The method is part of the endpoint identity. Studies measuring the same quantity by a different method are held as separate endpoints.

Notes

An exposure marker for the administered compound, not a health outcome: a rise demonstrates absorption, not benefit, and an edge resting only on this is a pharmacokinetic claim and should be graded as one. The near-miss is plasma serotonin (5-HT), its immediate metabolic product, measured in the SAME platelet-poor plasma sample on the same assay run - and the two dissociate: PMID 26031193 found this rose significantly (p<0.001) while serotonin did not move. Precursor and product are not interchangeable. Platelet-poor preparation matters because platelet lysis contaminates the serotonin measurement but not this one.