A 49-year-old man comes to the office for follow-up. A friend was recently diagnosed with gout, and the patient is anxious that he will also develop gout. The patient states that he had read "something about a diet called DASH that reduces the excess of uric acid in the blood and reduces the risk of gout." He would like to try the diet but asks if a less strict version would nevertheless help to reduce his chances of developing gout. Based on the abstract, which of the following is true about the magnitude of the risk of gout among patients adopting a Western diet in the highest fifth as compared to patients adopting a Western diet in the lowest fifth?

Question

A 49-year-old man comes to the office for follow-up.  A friend was recently diagnosed with gout, and the patient is anxious that he will also develop gout.  The patient states that he had read "something about a diet called DASH that reduces the excess of uric acid in the blood and reduces the risk of gout."  He would like to try the diet but asks if a less strict version would nevertheless help to reduce his chances of developing gout. Based on the abstract, which of the following is true about the magnitude of the risk of gout among patients adopting a Western diet in the highest fifth as compared to patients adopting a Western diet in the lowest fifth?

Quizplus · Accepted Answer

Explanation: Relative risk (RR) can be calculated in observational or experimental follow-up studies as follows: RR = Risk of disease in exposed group / risk of disease in unexposed group The RR usually indicates how high or low the risk for disease is among the exposed compared to the unexposed group. However, the RR can also be extended to compare risk for disease at different levels of an intervention or risk factor. The comparison is interpreted depending on which group is used as the denominator (ie, reference group): RR <1.0 indicates decreased risk in the group in the numerator RR = 1.0 indicates no difference in risk between the groups RR >1.0 indicates increased risk in the group in the numerator In this case, the numerator is the group of patients adopting a Western diet in the highest fifth, whereas the denominator (ie, reference group) is the group of patients adopting a Western diet in the lowest fifth. Therefore: RR = (348 / 192,778) / (287 / 190,572) = 0.0018 / 0.0015 = ~1.2 RR = 1.2 (= 120%) indicates that adopting a Western diet in the highest fifth increases the risk of gout by 20% (= 1.2 - 1 = 120% - 100%) when compared to adopting a Western diet in the lowest fifth (Choices A and B). (Choices D and E) Assuming the reference group (ie, denominator) is patients adopting a Western diet in the highest fifth, the RR can be calculated as follows: RR = (287 / 190,572) / (348 / 192,778) = 0.0015 / 0.0018 = ~0.83 RR = 0.83 indicates that the risk of gout among patients adopting a Western diet in the lowest fifth is 0.83 times (ie, 83%) the risk of gout among patients adopting Western diet in the highest fifth. An alternate interpretation is that adopting a Western diet in the lowest fifth is associated with a 17% (= 1 − 0.83 = 0.17) decrease in risk for gout when compared to adopting a Western diet in the highest fifth. Educational objective: Relative risk is a measure of the strength of association between exposure and disease in follow-up studies. Typically, it is the risk of the exposed group divided by the risk of the unexposed group. However, the exposure status may be redefined to designate different levels of an intervention or risk factor.

A 49-Year-Old Man Comes to the Office for Follow-Up