Molecular genotyping for identification of molar pregnancies

The test is batched and performed every Monday. The test itself takes 3 working days to complete

Background

Accurate diagnosis of molar pregnancies as partial or complete hydatidiform moles is important for determining risk of subsequent gestational trophoblastic neoplasia and appropriate patient follow-up.

Purpose of test

The test compares the short tandem repeat (STR) profile of maternal (decidual) and placental (villous) tissue. This is achieved by PCR amplification of multiple STR loci using fluorescently labelled PCR primers from the GenePrint-24 STR kit (Promega, Madison, WI, USA) followed by sizing of the PCR products by capillary electrophoresis to determine the genotype of the pregnancy.

Expected test result

Complete mole / Partial mole / Non-molar pregnancy

Caveats

DNA integrity and concentration must meet assay requirements. Cross contamination of maternal and placental tissue may result in inaccurate results. The results of this test must be correlated with histological findings and any other relevant ancillary investigations (e.g. p57 immunohistochemical staining) and clinical findings (e.g. presence of a fetus and exclusion of multiple pregnancies). Mosaic conceptions may generate complicated genotyping results which can be challenging to interpret. Chromosomal trisomies may confound interpretation if the number of informative loci is inadequate. The genotyping result of biparental diploidy may be misinterpreted as non-molar if morphological features and p57 results are not correlated with.

Proficiency testing

Alternative performance assessment programme.

Reference

Lipata F et al. Precise DNA genotyping diagnosis of hydatidiform mole. Obstet Gynecol 2010; 115: 784-94.