In addition to chromosome abnormalities, this test can detect conditions associated with an elevated alpha fetoprotein (AFP). Such conditions include open neural tube defects, abdominal wall defects, esophageal and duodenal atresia, and congenital hydronephrosis.
Fetal blood contamination of the specimen can cause an elevated AFP; therefore, a fetal hemoglobin test is performed to rule out a false-positive result. An acetylcholinesterase test is also performed to further clarify the cause of the elevated AFP. The presence of acetylcholinesterase is associated with an open neural tube defect, anencephaly, gastroschisis, other ventral wall defects, teratoma, hypoplasia of heart and lung, fetal demise, and fetal hemoglobin contamination.
The fetal hemoglobin and the acetylcholinesterase tests are reported using separate CPT codes at an additional charge.