| PHI | passive hemagglutination inhibition; past history of illness; phosphohexose isomerase; physiological... |
|---|---|
| PI | first meiotic prophase; isoelectric point; pacing impulse; package insert; pancreatic insufficiency;... |
| RI | radiation intensity; radioactive isotope; radioimmunology; recession index; recombinant inbred [stra... |
| R-SIRS | Revised Seriousness of Illness Rating Scale |
| SI | International System of Units [Fr. le Systeme International d'Unites]; sacroiliac; saline infusion; ... |