Misdiagnosis of homozygous alpha-thalassaemia 1 may occur if polymerase chain reaction alone is used in prenatal diagnosis

Tsang Ming Ko, Li Hui Tseng, Hsiao Lin Hwa, Pi Mei Hsu, Shwu Fan Li, Jo Yu Chu, Pei Jen Lu, Tzu Yao Lee, Sou Ming Chuang

Research output: Contribution to journalArticlepeer-review


The polymerase chain reaction (PCR) is a quite sensitive diagnostic tool but its specificity may be hampered because of contamination of foreign DNA. In order to determine the diagnostic accuracy of PCR in diseases due to gross gene deletion, a total of 180 fetuses at risk of homozygous South-East Asian deletion (SEA) of alpha-globin genes were included for study. Both PCR and Southern hybridization (SH) were performed. By PCR, three of 43 affected fetuses were misdiagnosed as heterozygotes; four of 50 normal fetuses were misdiagnosed as heterozygotes; and four of 87 heterozygotes were misdiagnosed, two as normal and two as affected. Misdiagnosis in affected and normal fetuses was most likely due to maternal DNA contamination, while misdiagnosis in heterozygotes was probably due to a failed PCR. In the experiments with PCR in which we added DNA from a carrier woman to an affected or a normal fetus, a level of 1/64 and 1/16 contamination resulted in the appearance of normal and SEA breakpoint sequences, respectively. In the SH experiments using artificially contaminated DNA, a level of 1/4 contamination showed the normal and SEA bands, respectively, while a contamination level lower than 1/8 and 1/16 respectively did not reveal contamination bands. The high sensitivity of PCR makes it easier to amplify contaminated DNA. For accurate prenatal diagnosis, PCR should be performed very carefully and SH seems to be a useful back-up.

Original languageEnglish (US)
Pages (from-to)505-509
Number of pages5
JournalPrenatal Diagnosis
Issue number6
StatePublished - Jun 1997
Externally publishedYes


  • Alpha-thalassaemia
  • Misdiagnosis
  • Polymerase chain reaction
  • Prenatal diagnosis

ASJC Scopus subject areas

  • Genetics(clinical)
  • Obstetrics and Gynecology


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