Clinical judgment and sometimes ethical judgment enter into these decisions where there are often no right or wrong answers and where there are no textbooks or RCTs that tell us what to do.
predecessor - something that precedes and indicates the approach of something or someone. harbinger, herald, forerunner, precursor. indicant, indication - something that serves to indicate or suggest; an indication of foul play; indications of strain; symptoms are the prime indicants of disease.
Precursor: Forerunner. That which precedes or is derived from an available source. The term precursor is applied to an inactive substance converted to an active one (such as an enzyme, vitamin, or hormone). The term precursor applies to any chemical that is transformed into another. From the Latin praecursor, composed of prae- (or pre-), before + curro to run = to run before.