Semen test PRA refers to spermatozoa that move forward quickly and in a straight line in a sperm viability test. In sperm examination, the fourth edition of the international version, the vitality of sperm is divided into four grades ABCD, grade A has the highest vitality, for sperm that can move forward quickly and in a straight line, grade B is for sperm that move forward slowly or without direction, grade C is for sperm that do not move forward, and grade D is for sperm that is not viable. PR means forward-moving sperm, so it includes grade A, grade B, and it is indicated by PR (A) and PR (B) in the examination, so PR (A) in semen examination refers to the sperm with the highest sperm vitality that moves forward in a fast and straight line. To summarize, to determine sperm vitality, it is mainly based on the percentage of sperm in class A and B. The higher the sum of the two, the greater the sperm vitality.