There are multiple definitions:

1. free erythrocytic porphyrin(English)

   • Erythrocyte, Clinical chemistry

2. first-episode psychosis(English)

   • outcome is highly variable, ranging from early sustained recovery to antipsychotic treatment resistance from the onset of illness
   • DHEA-S, DSI, DUP, EEG, POE, PTSD, SP, SUD, TTP, UHR
   • Psychiatry, Prognosis, Cognitive function, Psychosis
   • https://doi.org…psyt.2018.00580
   • https://doi.org…chc.2021.08.002

3. fractional excretion of phosphorus(English)

   • FEPi, PTH
   • Thyroid and parathyroid, Clinical chemistry
   • https://doi.org….1172/JCI111035

4. fibroepithelial polyp(English)

   • CSK, HPV, SK, VSK
   • Virology, Genitals
   • https://doi.org…8177(03)00184-9