Using PCR in preimplantation genetic disease diagnosis

Preimplantation diagnosis of genetic disease can be accomplished by embryo biopsy or polar body analysis using in-vitro gene amplification (PCR). PCR analysis of single cells is subject to a number of errors which decrease the reliability of the diagnosis. Using realistic assumptions about error rates based on experimental data, we analyse some of the practical consequences to be faced by whose wishing to use this diagnostic procedure. We considered both autosomal dominant and recessive diseases. We calculate the probability of making mistakes in the diagnosis, assuming a realistic range in the magnitude of PCR efficiency, cell transfer, and contamination errors. We conclude that, in general, analysing blastomeres is subject to less mis-diagnosis than polar body analysis, except in the case of dominant diseases which are caused by genes which lie extremely close to the centromere. We also show that typing multiple blastomeres from a single embryo or combining polar body typing with blastomere analysis results in significantly lower levels of mis-diagnosis with unacceptable consequences. The preimplantation diagnosis of X-linked diseases based upon Y chromosome sequence analysis is also discussed.