Last reviewed dd mmm yyyy. Last edited dd mmm yyyy
Grade A
Based on a meta-analysis or at least one randomised controlled trial
Grade B
Based on at least one well-designed, but not necessarily controlled study, including case control and comparative studies
Grade C
Based on expert reports or opinions
Add information to this page that would be handy to have on hand during a consultation, such as a web address or phone number. This information will always be displayed when you visit this page