DNA testing is not always as straight forward as obtaining a buccal swab sample and using RFLP and PCR techniques to gain data from it. In some situations a person is not alive or available to give a new DNA sample, so an older or more abstracted one must be tested. Before this can happen, however, a preliminary test must be carried out on the sample to ensure that it will give accurate DNA results. This test is known as ‘viability testing’.
Viability testing is not carried out on every DNA sample sent to a laboratory, but because DNA testing takes time and costs money, any samples that may not give accurate results are subjected to viability testing beforehand. If the sample is, indeed, too old to give a decent result then the laboratory has saved itself a considerable amount of money and time.
If you do have an old or very small DNA sample such as a hair or a used toothbrush then it’s always best to make a phone call to the DNA testing laboratory you intend to use. They will discuss with you whether the sample is likely to provide conclusive data and how you should send it in. You may find that they send you a specific pot or envelope to send to them so that the sample doesn’t get damaged. You should also take this opportunity to ask about the price of viability testing for your individual sample type. Price can vary depending on the sample size and condition, as well as there being a variation between DNA testing laboratories.
Viability testing can be used for any purpose at all, providing the sample is protected when it is sent. Whether it needs to be used for paternity testing, to determine whether the offspring of the person being tested could inherit a genetic condition or to find out if a person is the sibling of a person this can all be done with preliminary viability testing. The best way to get the most reliable results is to get a buccal swab from the person, if at all possible, but when this cannot be done viability testing carried out on an older or smaller sample can also produce accurate results.