| NASA | National Aeronautics and Space Administration |
|---|---|
| PAS | para aminosalicylate; Parent Attitude Scale; patient administration system; patient appointments and... |
| PES | Patient Escort Service; photoelectron spectroscopy; physicians' equity services; polyethylene sulfon... |
| PLES | parallel-line equal space |
| RRS | retrorectal space; Richards-Rundle syndrome |