Thalassemia screening

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shyam Patel [2]

Overview

Screening programs have been instituted in a variety of countries recently to help prevent birth of children with thalassemia. In Iran, for example, a national screening program has been intacted and has been successful. Screening programs employ molecular diagnostics such as polymerase chain reaction (PCR) or hemoglobin electrophoresis in order to detect thalassemias. However, there are numerous barriers to screening including high costs and lack of education about thalassemias.

Screening

Premarital screening is employed in countries that are endemic to thalassemia. In countries where screening is done, this can be an effective way to avoid the birth of children with thalassmia.[1] However, certain countries with high prevalence of thalassemia do not incorporate screening methods due to a variety of reasons (below).[1] Screening policy exists on both sides of the island of Cyprus to reduce the incidence of thalassemia, which since the program's implementation in the 1970s (which also includes pre-natal screening and abortion) has reduced the number of children born with the hereditary blood disease from 1 out of every 158 births to almost zero.[2] In Iran, the Ministry of Health approved a national screening program in 1996 for premarital screening. This national screening program was enacted after a 5-year pilot program was in place. The screening program provided counseling to couples at risk. The goal of this program was to reduce the social and financial burden of thalassemia in Iran.[3] This program has been found to be effective and feasible.PMC527661

Methodology of Detection

  • Polymerase chain reaction (PCR): The preferred method of thalassemia screening is PCR amplification of DNA from fetal trophoblastic tissue or amniotic fluid. Amniotic fluid is obtained from amniocentesis or from chorionic villus sampling.[4] If a newborn has the mutant globin chain within its germline DNA, PCR will amplify this DNA and will the mutation will be readily detectable.
    • Risks: There is a risk for false negative testing, in which a patient truly has thalassemia but no mutant PCR product is amplified. Maternal DNA contamination can also a false negative test result. In order to bypass the possibility of false negatives, multiple confirmatory tests can be done, including the amplification refractory mutation system and reverse oligonucleotide hybridization.[4]
    • Benefits: The advantages of PCR are the high sensitivity and low cost of the test.
  • Hemoglobin electrophoresis: Analysis of globin gene products on gel electrophoresis can help make a diagnosis of thalassemia.[4]

Barriers to Effective Screening

There are numerous barriers to effective screening for thalassemia.[3]

  • Costs of screening
  • Lack of awareness of availability screening
  • Unwillingness to participate in screening
  • Lack of concern about thalassemia
  • Absence of formalized screening initiatives or programs in certain countries

References

  1. 1.0 1.1 Waheed F, Fisher C, Awofeso A, Stanley D (2016). "Carrier screening for beta-thalassemia in the Maldives: perceptions of parents of affected children who did not take part in screening and its consequences.". J Community Genet. 7 (3): 243–53. PMC 4960032Freely accessible. PMID 27393346. doi:10.1007/s12687-016-0273-5. 
  2. Leung NT, Lau TK, Chung TKH (2005). "Thalassemia screening in pregnancy". Curr Opinion in Ob Gyn. 17: 129–34. 
  3. 3.0 3.1 Zeinalian M, Nobari RF, Moafi A, Salehi M, Hashemzadeh-Chaleshtori M (2013). "Two decades of pre-marital screening for beta-thalassemia in central Iran.". J Community Genet. 4 (4): 517–22. PMC 3773316Freely accessible. PMID 23467976. doi:10.1007/s12687-013-0142-4. 
  4. 4.0 4.1 4.2 Cao A, Kan YW (2013). "The prevention of thalassemia.". Cold Spring Harb Perspect Med. 3 (2): a011775. PMC 3552345Freely accessible. PMID 23378598. doi:10.1101/cshperspect.a011775. 



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