If the scientific goal is knowledge of normal human physiology or psychology, then the representative population would be “healthy” subjects, or those individuals who are free of a disease or condition. Of course, no physician or scientist can ever prove that an individual is completely healthy. Accordingly, those so called “healthy” subjects can only be said to be free of certain specified attributes of non-health. For example, although an individual may have a normal electrocardiogram, the physician cannot say that he or she does not have heart disease. In some cases, this representation of normal physiology may then be compared with those subjects affected with the disease or disorder of interest.
Potential subjects that will be included in the healthy population of a research study must be tested to demonstrate they do not possess the pertinent attributes of non-health. The pertinent attributes of non-health are determined by the investigator and will be protocol specific. Examples of the type of tests that may be conducted in this assessment include questionnaires, a physical examination by a licensed health care practitioner, a review of the subject’s medical record, and/or blood and urine testing. The Yale New Haven Hospital Laboratory Manual contains guidance on collection of specimens.
If the purpose of these tests is to exclude potential subjects that have attributes of non-health, the subject is expected to have normal physiology, and any results should be within normal limits. Therefore, if the investigator (who may not be the subject’s treating physician) finds abnormal results (attributes of non-health), he/she should ordinarily refer the subject to his/her health care practitioner.