When the Clostridia species are overabundant in [a] stool test, do you then conduct [a] microbial organic acids test to determine whether the overgrowth of species [is] pathogenic?

Not generally, and it depends what still tells you you’re talking about, but if you’re talking about the Doctor’s Data, actually you can do a follow-up test with Doctor’s Data that will tell you if those species are pathogenic. That’s probably the best way to do it.