Use of PCR in the Diagnosis of Monogenic Disease

Abstract

Since the fall of 1987, PCR technology has had a revolutionary impact upon the prenatal diagnosis of single gene disorders and carrier testing for these disorders. PCR technology has not yet expanded the repertoire of diseases which can be detected, but it has greatly expanded the options of the laboratory diagnostician. At Johns Hopkins it has allowed us to diagnose disorders with greater speed, greater accuracy, and with greater technical flexibility. Examples illustrating each of these improvements follow. Before October 1987, we carried out prenatal diagnosis of sickle cell anemia by Southern blotting for the mutation which usually required two or more weeks from the date of fetal sampling. Since October 1987, we have carried out these diagnoses by PCR techniques in two to four days from fetal sampling. Prior to October 1987, nearly all our prenatal diagnoses of β-thalassemia were accomplished through indirect detection via linked DNA polymorphisms in the β-globin cluster. Again, this work usually took two to four weeks to accomplish. Since October 1987, all our prenatal diagnoses of β-thalassemia have been carried out by direct detection of the disease-producing mutations after PCR amplification of regions of the β-globin gene. These methods provide increased accuracy and diagnosis usually within one week. Improved technical flexibility has meant that 1) if we are unable to determine a β-thalassemia mutation in one parent or another, we can study DNA polymorphisms in the β-globin cluster in a day or two, or 2) we can determine the extent of maternal contamination quickly using sequence differences between mother and fetus. These are just some examples of what PCR has meant to the gene diagnostic enterprise.