|
|
|
front |1 |2 |3 |4 |5 |6 |7 |8 |9 |10 |11 |12 |13 |14 |15 |16 |17 |18 |19 |20 |21 |22 |23 |24 |25 |26 |27 |28 |29 |30 |31 |32 |33 |34 |35 |36 |37 |38 |39 |40 |41 |review |
 |
When selected from
hospitals, it is essential to choose patients with other diseases, not with
the disease under question and if possible, preferably from same hospital
from where the cases were selected.
For example when the association between lung cancer and smoking is to be studied, if lung cancer cases were selected as study group, thyroid cancer patients can be taken as controls from the same hospital. |