| OA | Osteo-Arthritis = DJD |
|---|---|
| OA | obstructive apnea; occipital artery; occipito-anterior; occiput anterior; octanoic acid; ocular albinism; [o]esophageal atresia; old age; oleic acid; opiate analgesia; opsonic activity; optic atrophy; oral alimentation; orotic acid; osteoarthritis; osteoarthrosis; ovalbumin; overall assessment; Overeaters Anonymous; oxalic acid |
| OA/BVM | oral airway/bag-valve-mask |
| OAA | Old Age Assistance; Older Americans Act; Opticians Association of America; oxaloacetic acid |
| OAAD | ovarian ascorbic acid depletion |
| OAB | ABO blood group; old age benefits |
| OABP | organic anion binding protein |
| OAD | obstructive airway disease; organic anionic dye |
| OADC | oleate-albumin-dextrose-catalase [medium] |
| OAE | otoacoustic emission |