Question

Of 2,872 persons who had received radiation treatment in childhood because of an enlarged thymus, 24 persons developed thyroid cancer and 52 persons developed a benign thyroid tumor during follow-up period. A comparison group consisted of 5,055 children who had received no such treatment (brothers and sisters of the children who had received radiation treatment). During the follow-up period, none of the comparison group developed thyroid cancer, but 6 persons developed benign thyroid tumors. Calculate the relative risk for benign thyroid tumors: _____ and interpret your result. (1.5 point for calculation and 0.5 for interpretation. Please show details of your calculation)

Answer 1

Answer: 15.2498 approximately 15

Explanation:

The formula for relative risk is

a/(a+b) ÷ c/(c+d)

Where a= number of those exposed to the risk factor and who have the disease

b= number of those exposed to the risk factor but who don't have the disease

c= number of those not exposed to the risk factor but who have the disease

d= number of those not exposed to the risk factor and who don't have the disease

So, a = 52

b = 2872-52=2820

c = 6

d = 5055-6=5049

RR = (52/2872) divided by (6/5055)

RR = 15.2498

This is the relative risk for Benign Thyroid Tumours

INTERPRETATION:

The ratio of

the risk of developing benign thyroid tumours for those exposed to radiation treatment in childhood

to the risk of developing benign thyroid tumours for those not exposed to radiation treatment in childhood

is 15:1 that is, 15persons to 1person.