What is the LPN Entrance Exam’s policy on testing for drugs or substances? The rule, it seems, mentions go to my blog conditions, namely, 1st and 2nd, that we should be aware of as being the most important: 1. The capacity of the LPN to distinguish between different substances. 2. The risk of making a mistake in interpreting some information by the LPN. 3. No extra or transference of information by the LPN.