There are multiple approaches you could try:

a) You could take short notes when you read the passage. This may help bring concentration when you read and also give you better understanding. You need to be careful though with time when you do this. I have seen people take this approach with good practice.

b) You could skim through the passage and come back once you read your question. This may not work with all passages

c) You could allot a specific time to reading the passage and then move over to the questions.

You would be best judge as to the option that would work for you. What works for one may not work for the other. I would suggest you try these approaches during your practice and decide on the one that suits you.