Examples: Not enough DNA in the sample (this normally comes from the White Blood Cells), the primers used in a PCR test (amplifying the DNA) do not bind properly, other markers for various tests don&#x27;t bind correctly, etc. Not-binding correctly could be a problem with the whole sample (ie something in the blood is throwing off the test, outside contamination by a bad draw, not documenting draw date properly and sample is expired).<p>With solid tissue samples (often embedded in paraffin wax), there can be extensive problems with the sample being prepared incorrectly. These are normally prepared on-site at your doctor&#x27;s office and there is a surprising amount of variation.