It certainly couldn't hurt to contact schools to be sure. I am in a similar situation. I originally graduated from college in 2008 & am doing post bac science courses, since I wasn't a science major. My understanding is that it doesn't matter when the class was taken, so long as your final grade met the DS's requirement AND you still have a relatively solid understanding of the subject. If not, it would be beneficial to retake, though not entirely necessary. But again, you may want to contact the schools for a solid answer.