| AcT | acceleration time |
|---|---|
| AHT | aggregation half time; antihyaluronidase titer; augmented histamine test; autogenous hamster tumor |
| APTI | airway pressure time index |
| APTT, aPTT | activated partial thromboplastin time |
| ATB | at the time of the bomb [A-bomb in Japan]; atrial tachycardia with block |