| RISA | radioactive iodinated serum albumin; radioimmunosorbent assay |
|---|---|
| RMA | rapid membrane assay; refuses medical advice; Registered Medical Assistant; relative medullary area;... |
| RRA | radioreceptor assay; registered record administrator |
| RTA | ray tracing algorithm; renal tubular acidosis; reverse transcriptase assay; road traffic accident |
| RVRA | renal vein rein activity; renal venous renin assay |