Sentence Correction

Hi,

I am still trying to grasp and crystalize the concept of pronoun antecedent. It seems from this example that if you want to make the pronoun antecedent clear, in those cases where you have several of them, you should put them in parallel structure to make it clear that you're referring to the same antecedent which is close to the pronoun? Can someone elaborate on this? Thanks!

Any medical test will sometimes fail to detect a condition when it is present and indicate that there is one when it is not (wrong original)
Right choice: a condition when it is present and indicate that it is present

OG explanation for the wrong original: There is one leaves it in the final clause without a referent

OG explanation for the right choice: The three uses of the pronoun it refer clearly to condition, and the two parts of the sentence correspond

your thinking is quite clear.
https://www.towson.edu/ows/pro_antagree.htm this will give a good perspective about pronoun antecedent.
parallel structure is required for antecedent reference.