In my case I had some testing done immediately after I was diagnosed with pulmonary embolisms while I was still in the hospital. While the blood chemistry tests are useless while on warfarin and heparin the genetic tests came back with useful information. My hematologist found out that I have heterozygous Factor V Leiden.
Factor V Leiden is a mutation of one of the pieces of genetic information that tells the blood how to turn off clotting when it isn't needed. In my case it is heterozygous. This means that I have one good copy and one bad copy of the Factor V Leiden gene. The mutated versions of my turn off system don't match the chemical that is responsible for turning clotting off. I am lucky in that the other half of my turn off system is programed correctly. This gives me a much lower chance of having clots than if I had two mutated genes.
Being heterozygous also gives me a hint about why I have Factor V Leiden. One of my parents passed on the gene to me. This means that at least one of my parents has either homozygous or heterozygous Factor V Leiden.
When I was first diagnosed one of the first questions to my hematologist was, "should my family be tested?" My hematologist felt that my clotting condition wasn't a major risk so genetic testing wouldn't be warranted. He also noted that it would be helpful to let family members know that they may be at risk.
While informing my family about the risk we discovered that someone on my mom's side also has Factor V Leiden. This seemed to be the missing link. We assumed that my mother was the carrier that gave me my gene.
Fast forward a few years...
This last fall my dad had to go in for hernia repair surgery. Knowing my history he shared our family history of pulmonary embolisms and my Factor V Leiden diagnosis. Arrangements were made to test him for Factor V Leiden. We expected it to be negative due to history on my mom's side. The tests came back positive. He also has heterozygous Factor V Leiden. Arrangements were made to consult with a hematologist and make clotting plans for his surgery. His hematologist, the same one that I see, cleared him for surgery with no anticoagulants as he felt that laparoscopic hernia repair was a very low risk surgery.
Come May we discovered that my mom had a number of benign tumors that needed to be removed. Due to the history she also asked for a Factor V Leiden test. Her test came back negative. Despite that her surgeon has her on Lovenox injections. Abdominal surgery is a very high risk for clotting in ALL people. New standards for clot prevention are demanding that preventative anticoagulation be used after high risk surgeries. While in recovery her heart rate was up. As an additional precaution she was sent to have a chest CT to make sure that she didn't have clots. She was clear. We now need to make it through recovery with no clots. I am hoping that her lack of FVL diagnosis and the daily Lovenox injections keep her clot free.
If you would like more information about who should be tested for thrombophilia please see this Clot Connect article.