Fetal Blood Contamination, Amniotic Fluid (FBC-R)
Bovine Serum Contamination, Amniotic Fluid (BSA-R)

Prenatal Screening Laboratory

Counterimmunoelectrophoresis and radialimmunodiffusion

---

Specimen Required:

Amniotic fluid: 1 mL

Include 1 mL whole fluid if visibly bloody

Room temperature or 4°C

Days Test Set Up:

FBC - Monday-Thursday
BSA - Friday.

Analytic Time:

24 hours

Reference Values:

No precipitin band = Normal

CPT Code(s):

86331, 86185

Relevance:

The presence of fetal serum in amniotic fluid can contribute to elevated amniotic fluid alpha-fetoprotein or positive acetylcholinesterase (AChE).

Notes:

The presence of fetal bovine serum albumin (BSA), another cause of false positive AChE results, can be confirmed with this same method.

Reference(s)

• Wald NJ, Cuckle HS, Nanchahal K: Amniotic fluid acetylcholinesterase measurement in the prenatal diagnosis of open neural tube defects. Second report of the collaborative acetylcholinesterase study. Prenat Diagn, 9:813-827, 1989.
• Barlow RD, Cuckle HS, Wald NJ, et al.: False positive gel-acetylcholinesterase results in blood-stained amniotic fluids. Br J Obstet Gynæcol, 89:821, 1982.
• Doran TA, Allen LC, Pirani BBK, et al.: False positive amniotic fluid alpha-fetoprotein levels resulting from contamination with fetal blood: Results of an experiment. Am J Obstet Gynecol, 127:799, 1977.