Refer to Exercise 13 on page 120 for a description of a study about the drug natalizumab.
Exercise 13
Approximately 85% of patients diagnosed with multiple sclerosis have attacks—often called relapses—of neurologic problems. The relapses are followed by periods during which symptoms improve partially or fully. This form of the disease is called relapsing-remitting multiple sclerosis (RRMS). In a double-blind study, researchers tested whether the drug natalizumab reduces the annual relapse rate for RRMS patients. A total of 942 RRMS patients ages 18 to 50 years, inclusive, were randomly assigned to receive the drug or a placebo by intravenous infusion for 120 weeks. The study concluded that the drug reduces the relapse rate.
a. What does it mean that the study is double-blind? How could it be accomplished?
b. What are the explanatory and response variables?
c. What is the conclusion of the study? Does this mean there is causality or only an association between the two variables? Explain.
d. In the journal article, many of the researchers reported that they have received consulting fees, lecture fees, and grant support from the company that manufactures natalizumab. Why is it important that this is stated in the article?