Retinoblastoma: a diagnostic model for India.

PURPOSE: Molecular genetic diagnostics for retinoblastoma are prerequisite for accurate risk prediction and effective management. Developing a retinoblastoma diagnostic model to establish a flow for laboratory tests is thus a necessity for tertiary ophthalmic institutions. An efficient diagnostic model could reduce the overall health care costs, redirect the resources to the high risk group and also avoid unnecessary worry for families. To the best of our knowledge there has hitherto been no comprehensive diagnostic model for retinoblastoma implemented in any institution in India. METHODS AND DISCUSSION: The diagnostic model demonstrates the logical and practical flow of various genetics tests like karyotyping, loss of heterozygosity analysis, molecular deletion, linkage analysis (familial cases), mutation screening of -CGA exons first and then non-CGA exons, methylation screening of RB1 and essential promoter regions screening in a laboratory. Conclusions: The diagnostic model proposed offers acomprehensive methodology to identify the causative two-hits for retinoblastomas that could be used while genetic counseling families. This model is applicable in tertiary hospitals in India and neighboring countries, which have the highest incidence of retinoblastoma and fertility rates in the world. We suggest that this diagnostic model could also be applied with modification for other cancers.

CGA codons multiplex PCR in rapid diagnosis of retinoblastoma.

Background: Multiplex polymerase chain reaction allows amplification of multiple target sequences of a genome under identical conditions in a single tube. This "one-shot" polymerase chain reaction detection is time and cost effective when large or multiple genes, with many target fragments are investigated. This is applicable for retinoblastoma susceptibility gene having 27 exons with recurrent mutations reported at most of the 12 CGA codons. Materials and Methods: Multiplex polymerase chain reaction assay for the amplification of 12 CGA codons, which constitutes about 50 % of retinoblastoma susceptibility gene mutations has been designed. The time and cost (includes only reagent cost) involved in both multiplex and uniplex polymerase chain reaction was also calculated. Results: Twelve CGA codons were multiplexed in 5 instead of 12 uniplex polymerase chain reactions, which took 36 hours and 9.78 US$ whereas multiplex polymerase chain reaction took 15 hours and 6.88 US$. Multiplex polymerase chain reaction method saved 58.3% of time and 29.6% of cost over uniplex polymerase chain reaction. Conclusion: Saving time by more than half and cost by nearly a third would help clinicians and geneticists while counseling retinoblastoma patients.

Molecular-genetic analysis of two cases with retinoblastoma: benefits for disease management.

Effective counselling and management of retinoblastoma families using genetic information is presently practised in many parts of the world. We studied histopathological, chromosomal and molecular-genetic data of two retinoblastoma patients from India. The two patients, one with bilateral and the other with unilateral retinoblastoma, underwent complete ophthalmic examination, cytogenetic study, retinoblastoma gene (RB1) mutational analysis and RB1 promoter region methylation screening. In the bilateral retinoblastoma patient deletion of chromosome region 13q14 in peripheral blood lymphocytes and a hemizygous novel 8-bp deletion in exon 4 of RB1 in tumour sample were observed. In the unilaterally affected patient CGA to TGA transition protein truncation mutations were observed in exons 8 and 14 of RB1.