| PKAR | protein kinase activation ratio |
|---|---|
| RNAA | radiochemical neutron activation analysis |
| RVA | re-entrant ventricular arrhythmia; right ventricle activation; right vertebral artery |
| TAT | tetanus antitoxin; thematic apperception test; thematic aptitude test; thrombin-antithrombin complex... |
| TBNA | total body neutron activation; treated but not admitted |