Genetic Testing Back

Specimen Requirements Printable Version

Tests Explained Printable Version


Tests Explained


Thrombophilia panel: (Total 9 genetic Loci)


Prothrombin is a protein circulating in the blood essential for clotting. A mutation in the Prothrombin gene results in excess production of the prothrombin protein with the result that the blood may over clot. Mutations in this gene may lead to recurrent pregnancy loss, fetal death and pre-eclampsia. It may also result in placental abruption; the abnormal separation of the placenta after 20 weeks of gestation and prior to birth, where the placental lining separates from the uterus of the mother. It is the most common cause of late pregnancy bleeding.

Antithrombin is a protein in the blood that blocks the formation of blood clots by inhibiting the procoagulation (causing the blood to clot) factors II, IX, X and XI. It is

an inherited condition in which an abnormal gene (inherited from a parent with the disease) leads to low levels or reduced function of the protein. This can cause abnormal blood clotting.

Factor V Leiden. Factor V is a protein essential for normal blood clotting. Once the blood has sufficiently clotted, the Factor V Leiden protein becomes inactivated. Some people inherit a defective Factor V gene, Factor V Leiden (a point mutation). This genetic defect makes the Factor V Leiden protein much more difficult to inactivate, resulting in excessive clotting. The Factor V Leiden defect has been associated with recurrent pregnancy loss, late abortions, fetal death/growth retardation and pregnancy complications such as pre-eclampsia.

Factor XIII is a protein that is part of the cascade of clotting factors involved in the process of forming a protective blood clot. Genetic variations in the gene for the Factor XIII protein have been associated with an increased ability to form a blood clot. Women who are homozygous for Factor XIII mutations also have a high risk for recurrent spontaneous abortion.

MTHFR is a recessive gene that when it carries one or more mutations, may lead to accumulation of high levels of homocysteine subsequently promoting thrombophilia. Both alleles of the MTHFR gene (homozygous mutant) need to have the mutation in order to have a noticeable effect. Mutations of the MTHFR gene are associated with a higher risk for recurrent abortions and birth defects. It may also lead to third trimester and post-partum complications.

Plasminogen Activator Inhibitor – 1 (PAI-1). Plasminogen activator is an enzyme involved in the process of breaking down blood clots. Elevated levels of this enzyme (the inhibitor for plasminogen activator) cause excessive clotting as breaking down blood clots is blocked. Abnormal levels of PAI-1 may cause recurrent pregnancy loss, pre-eclampsia, fetal growth retardation and fetal death.

Human platelet antigens (HPA1) can stimulate production of allo-antibodies (antibodies against other people's antigens) in recipients of transfused platelets from donors with different HPAs. These antibodies cause neonatal alloimmune thrombocytopenia which is a disease that affects fetuses and newborns. Genetic differences between the fetus and mother may result in the expression of certain antigens by fetal platelets not expressed by the mother. Feto-maternal transfusions result in the recognition of these antigens by the mother's immune system as non-self, with the subsequent generation of allo-reactive antibodies which cross the placenta. Thrombocytopenia is mild, the affected neonates remain largely asymptomatic and no


intervention is needed. Cases of severe neonatal thrombocytopenia may exhibit hemorrhagic complication at or a few hours after delivery. The most serious complication is intracranial hemorrhage, leading to death in approximately 10%, or neurologic complications in 20% of cases.

APO-E gene provides instructions for making apolipoprotein E which combines with lipids in the body to form lipoproteins.

Lipoproteins are responsible for packaging cholesterol and other fats and carrying them through blood stream. Maintaining normal level of cholesterol is essential for prevention of cardiovascular disorder. There are at least three slightly different alleles of APO-E gene called e2, e3, & e4. Most common allele is e3. Allele e4 is associated with recurrent pregnancy loss.



Fragile X



Fragile X Syndrome – A genetic mutation found on the FMR1 gene on the X chromosome. A DNA test can be performed to determine if a woman carries the genetic mutation as either the complete mutation or the pre-mutation. Normally, the FMR1 gene contains between 6 and 55 repeats of the DNA nucleotide sequence CGG. In people with the fragile X syndrome, the FMR1 allele has over 230 repetitions. This mutation leads to the silencing of the fragile X-mental retardation protein (FMRP), which is believed to play important roles in learning and memory.


The pre-mutation (mild form) was found in about 20-30% of women suffering from premature ovarian failure. Each child of a woman carrying the pre-mutation has a 50% chance of receiving an X chromosome with the pre-mutation. There is also a chance a child will inherit a more severe version of the X chromosome resulting in the full mutation. The full mutation affects approximately 1 in 4,000 males and 1 in 8,000 females resulting in borderline to severe mental retardation.


Karyotyping (Chromosome Analysis)


Cells from the peripheral blood are cultured from both prospective parents for the purpose of checking the chromosome makeup. Abnormal karyotypes are a significant cause of recurrent miscarriage or infertility. Abnormalities may be extra or missing chromosomes, translocations, deletions and inversions. Karyotyping can identify the abnormalities and determine the anatomical, physical and physiological manifestations associated with them.