| RRA | radioreceptor assay; registered record administrator |
|---|---|
| RTA | ray tracing algorithm; renal tubular acidosis; reverse transcriptase assay; road traffic accident |
| SCCA | single-cell cytotoxicity assay |
| SPA | salt-poor albumin; sheep pulmonary adenomatosis; sperm penetration assay; spinal progressive amyotro... |
| TyRIA | thyroid radioisotope assay |