Dealing with departures from allocated treatments
For all the reasons given so far in this section, you will have realized that fair tests of treatments have to be planned carefully. The documents setting out these plans are known as research protocols.
However, the best-laid plans may not work out quite as intended – the treatments actually received by patients sometimes differ from those they were allocated. For example, patients may not take treatments as intended; or one of the treatments may not be given because supplies or personnel become unavailable. If such discrepancies are discovered, the implications need to be considered and addressed carefully.
During the 1970s and 1980s, there were remarkable advances in the treatment of children with acute lymphoblastic leukaemia, the most common type of leukaemia in this age group. However, it was puzzling that American children were doing substantially better than British children who, on the face of it, were receiving exactly the same drug regimens. 
During a visit to a children’s cancer centre in California, an astute British statistician noticed that American children with leukaemia were being treated far more ‘aggressively’ with chemotherapy than children in the UK. The treatment had nasty side-effects (nausea, infection, anaemia, hair loss, and so on) and when these side-effects were particularly troublesome, British doctors and nurses, unlike their American counterparts, tended to reduce or pause the prescribed treatment.
This ‘gentler approach’ appears to have reduced the effectiveness of the treatment, and was probably a reason for the differences in British and American treatment success.