As of January 2016, samples of DNA test results demonstrating both paternal inclusion and exclusion are available to download on the websites of both Genex Diagnostics and Home DNA Direct. A test demonstrates paternal inclusion if all of the loci tested are genetic matches, states Genex Diagnostics. Paternal exclusion eliminates the possibility of a man being the father and occurs when at least two loci do not match.
It is not possible to prove paternity with 100 percent certainty, although DNA tests provide about 99.9 percent accuracy, according to Home DNA Direct. The only 100-percent foolproof way to prove paternity is to test the DNA of every single man in the world.
The DNA tests issued at Genex Diagnostics examine 16 loci per man tested, explains the company's website. When possible, the laboratory staff also compares a sample of the mother's DNA to that of the child to determine which portions of the child's genetic makeup come from the mother. If a sample from the mother is not available, the laboratory staff is still able to compare the child's loci to those of the alleged father(s). The term locus refers to any region along the genome that is identifiable through genetic analysis, notes Mouse Genome Informatics.