Carrier detection and prenatal diagnosis constitute an important component of haemophilia management. Recent advances in molecular biology allows us to use the tools of molecular biology to give such a diagnosis early in the pregnancy with a much higher confidence. Because of lyonisation, diagnosis of a carrier by factor assay is imperfect and hence lacks sensitivity. Molecular diagnosis in such cases is robust.There are several techniques by which this diagnosis can be made.Though the preferred method is to do direct mutation studies, yet the complexities of factor VIII and factor IX genes may not make this approach easy or cost effective. Hence depending on the capability of the laboratory, education status of the family, availability of data through several generations and economic situation of the country, a combination of these techniques need to be adopted for optimum results. These techniques are broadly classified as indirect techniques through linkage analysis or direct detection of affected genes by a combination of screening and sequencing techniques.
Occasionally in our country even all the gene based techniques may prove inadequate and we may have to give prenatal diagnosis by antigen and clotting activity assay of the defective factor by cordocentesis between 17-20 weeks of gestation. For any prenatal diagnosis of haemophilia, prior detection of fetal sex either by USG or by molecular technique is necessary to decide whether any further work up is necessary or not? The present article describes various algorithms of carrier detection prenatal diagnosis of haemophilia that was found suitable in our country.
