Amniotic fluid alpha-fetoprotein assay (AFP)

Amniotic fluid alpha-fetoprotein is synthesized from fetal liver cells and yolk sac, and its concentration gradually rises from the beginning of pregnancy. The gestational age reaches a peak at 16 to 20 weeks, reaching 40 mg/L. It gradually decreases after 20 to 22 weeks, and decreases after 32 weeks. 25mg/L or so, and maintained until full term. Amniotic fluid AFP is higher than the mean, found in fetuses with no brain or spina bifida; also seen in many other malformations, such as congenital nephropathy, esophageal or intestinal atresia, umbilical hernia, cystic hydroma, teratoma teratoma, Rh blood group Disharmony, congenital stupidity, congenital gonadal dysplasia, etc. Basic Information Specialist classification: Oncology examination classification: immune examination Applicable gender: whether women are fasting: fasting Tips: Usually can be carried out in the middle of pregnancy 16 to 20 weeks. Normal value 20 to 48 mg/L (20 to 48 μg/ml). Clinical significance AFP can enter the maternal blood circulation through the amniotic fluid. In 85% of spina bifida and non-brain mothers, plasma AFP is elevated in the 16-18 weeks of gestation and has diagnostic value, but must be combined with clinical experience to avoid false positive errors. 1. AFP can enter amniotic fluid from an open neural tube and cause a significant increase in its content in amniotic fluid. The amniotic fluid alpha globulin value is 10 times higher than the normal value, indicating that the fetus has an open neural tube abnormality or is a brainless child. 2, also seen in a variety of other malformations, such as congenital nephropathy, esophageal or intestinal atresia, umbilical hernia, cystic hydroma, teratoma teratoma, Rh blood group disharmony, congenital stupid, congenital gonadal dysplasia and so on. 3. When severe fetal distress or intrauterine death is possible, the AFP content of amniotic fluid is several times higher than normal. High results may be diseases: spina bifida, no brain, fetal teratoma, pediatric congenital nephrotic syndrome, fetal distress Note before inspection: 1. The subject adjusts his mentality and avoids being too nervous. 2, amniocentesis is an invasive examination, puncture should be carefully decided, and the full understanding and consent of pregnant women and their families need to be obtained before surgery. Inspection process 1. Take the test tube for numbering. 2. Add reagents according to Table 1. 3. After adding PEG, place it for 10 minutes. 4. Determine the total radioactivity (T) of each tube. 5. Centrifuge at 3000r/min for 15min. 6. Carefully aspirate the supernatant. 7. Determine the radioactivity (B) of each tube precipitate. Not suitable for the crowd Those without examination indications should not be tested. Adverse reactions and risks 1, maternal injury: puncture needle stab wound blood vessels caused by abdominal wall hematoma uterine subserosal hematoma. Occasionally, amniotic fluid enters the maternal blood circulation from the puncture hole and causes amniotic fluid embolism. The bladder was not emptied before the puncture, and the bladder was injured. 2, damage to the fetus, placenta and umbilical cord: puncture needle damage to the fetus can occur bleeding, stab wounds and umbilical cord can also occur bleeding or hematoma. Therefore, the source of bleeding should be identified when taking hemorrhagic amniotic fluid. If you suspect that you are from a fetus, you should continue to listen to the fetal heart. 3, amniotic fluid leakage: postoperative amniotic fluid leakage from the needle hole, resulting in too little amniotic fluid, affecting fetal development, and even cause miscarriage or premature birth.