The medical equipment that is used for carrying out such screening tests is very different from the standard equipments that medical facilities use in diagnostic tests. Screening equipments are used to detect whether there is a possibility of the particular disease or medical condition on the other hand, diagnostic medical equipment is used to make measurements of the visible symptoms of the patient to determine the exact remedial procedure to be followed in the patient’s treatment.

There is however several adverse affects associated with carrying out screening procedures. Like most other medical procedures, screening tests carried out may not be completely perfect. The equipments that are usually used are not technologically top notch and not very well developed. As a result of this, they might prove to show inconsistent results. They might prove to show positive results for those who actually do not have the disease or may show negative for those who do have the disease and require treatment. Therefore they are not completely reliable. There are other adverse affects also related to such screening tests, for example, these tests almost always cause stress and anxiety for the patients, combined with exposure of the patient to radiation and chemicals. If false positive results are given by the equipment, then, unnecessary investigation and treatment of the disease would be carried out on the patient, leading to another set of negative affects. If the equipment detects false negative results, it would create a false sense of security for the patient and would in turn prolong his treatment, worsening his or her medical condition.
The usual types of screening that are carried out on a large scale basis in communities are, fetal screening, new born screening, screening for various kinds of cancers such as prostrate cancer or breast cancer, etc.

Because of the adverse affects of screening, the World Health organization published a set of principles in 1968 for carrying out screening which must be followed, these are applicable till date.