Help on nursing electrolytes project!?

I need help on an electrolytes project for school. Our teacher refuses to give us any clarification on anything and I don't understand what some of the criteria is asking. The first is, "Differentiation between an increase and decrease in the lab values." The second is, "diagnostic studies to determine the underlying cause of the alteration in lab values or assess for effects of the alteration". In this second one I am not quite sure what diagnostic studies are and have been trying to look online but no luck! I assume it is like blood tests, urinalysis, etc... Thank you sooooooo much !!!!!