What is a genetic test?

My inclination is to examine the fundamental assumptions before moving on. Many large mistakes get their start in some small detail or distinction. 

Some acceptable definitions:

 From NHGRI

http://www.genome.gov/19516567

I think this gives a sensible summary. It does not fully capture the character of genomic testing. 

From GINA http://www.gpo.gov/fdsys/pkg/PLAW-110publ233/html/PLAW-110publ233.htm

(7) Genetic test.--
                    ``(A) In general.--The term `genetic test' means an
                analysis of human DNA, RNA, chromosomes, proteins, or
                metabolites, that detects genotypes, mutations, or
                chromosomal changes.
                    ``(B) Exceptions.--The term `genetic test' does not
                mean--
                          ``(i) an analysis of proteins or metabolites
                      that does not detect genotypes, mutations, or
                      chromosomal changes; or
                          ``(ii) an analysis of proteins or metabolites
                      that is directly related to a manifested disease,
                      disorder, or pathological condition that could
                      reasonably be detected by a health care
                      professional with appropriate training and
                      expertise in the field of medicine involved.

 

I have not yet found in GINA a definition of 'genetic information' although that is what it intends to regulate.

 

Belmont Position:

I mean to take the position that the unique character of genetic information is that beyond the individual case it extends to additional knowledge of biological relatives. That knowledge may or may not be put to use. Genetic tests generate genetic information (the Latin 'genus' getting a workout there).

 

If we say that genetic testing is that which leads to a genetic diagnosis I am not sure we have solved the puzzle. The phrase "genetic diagnosis" is potentially both circular and incomplete (not sure Euclid would approve).  We used to be able to restrict ourselves to rare disorders - cytogenetic, single gene,  genomic, epigenetic.  Now that territory has extended considerably to including identity/paternity/forensics, ancestry/populations, common disease risk, other domains that we may not be able to enumerate in advance. 

 

The special character of genetic testing seems not to lie in the special risks associated with genetic testing. Green and Botkin (Ann Intern Med. 2003;138:571-575) took that apart very convincingly.

 

I agree with the position that it is not the technical platform that defines genetic testing.Lots of metabolic, protein, histology and even imaging tests lead to a specific genetic diagnosis

 

I take the position that it is the ability to make an inference about biological relatives - beginning with parents, sibs, and offspring - that accounts for the special quality of genetic testing. A test for Prader-Wili is a genetic test because of what one may conclude about family risk rather than the disease itself.  Sometimes a test is genetic and sometimes not. Plasma amino acids is a genetic test for PKU but not when it is used to assess general nutrition. Sometimes we do a test for a non-genetic reason and it uncovers a genetic diagnosis. Discuss.