Question

Community acquired methicillin resistant Staphylococcus aureus (CA-MRSA) is a cause of skin infections. A case-control study is conducted to explore the association between having a cat in the household and CA-MRSA. The results of the study are given below. CA-MRSA 146 230 No CA-MRSA 120 504 Cat in household No cat in household Information on this household composition, and exposure to children less than 12 years old was collected from participants. Stratified data are shown below. Calculate the OR for the relationship between cat ownership and CA-MRSA among those exposed and not exposed to young children in school. Please show your work. Not exposed to children CA-MRSA no CA-MRSA 120 Cat in household No cat in household 60 68 Exposed to children CA-MRSA no CA-MRSA Cat in household No cat in household 26 60 162 463

Answer 1

For Not exposed to children group => Odd ratio = (120/68)/(60/41) = (120*14)/(68*60) = 0.411

The odds are 0.411 that within not exposed to children group, having a cat will result in skin infection (CA-MRSA).

For exposed to children group => Odd ratio = (26/162)/(60/463) = (26*463)/(162*60) = 1.238

The odds are 1.238 that within exposed to children group, having a cat will result in skin infection (CA-MRSA).

Overall, if exposed to children, having a cat increases chances of infection.