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We developed Genetic-Epigenetic Tissue Mapping (GETMap) to determine the tissue composition of plasma DNA carrying genetic variants not present in the constitutional genome through comparing their methylation profiles with relevant tissues. We validated this approach by showing that, in pregnant women, circulating DNA carrying fetal-specific alleles was entirely placenta-derived. In lung-transplant recipients, we showed that, at 72 hours after transplantation, the lung contributed only a median of 17% to the plasma DNA carrying donor-specific alleles and hematopoietic cells contributed a median of 78%. In hepatocellular cancer patients, the liver was identified as the predominant source of plasma DNA carrying tumor-specific mutations. In a pregnant woman with lymphoma, plasma DNA molecules carrying cancer mutations and fetal-specific alleles were accurately shown to be derived from the lymphocytes and placenta, respectively. Analysis of tissue origin for plasma DNA carrying genetic variants is potentially useful for noninvasive prenatal testing, transplantation monitoring and cancer screening.

Cytogenetic aberrations may escape detection or recognition in traditional karyotyping. The past decade has seen an explosion of methodological advances in molecular cytogenetics technology. These cytogenetics techniques add color to the black and white world of conventional banding. Fluorescence in-situ hybridization (FISH) study has emerged as an indispensable tool for both basic and clinical research, as well as diagnostics, in leukemia and cancers. FISH can be used to identify chromosomal abnormalities through fluorescent labeled DNA probes that target specific DNA sequences. Subsequently, FISH-based tests such as multicolor karyotyping, comparative genomic hybridization (CGH) and array CGH have been used in emerging clinical applications as they enable resolution of complex karyotypic aberrations and whole global scanning of genomic imbalances. More recently, crossspecies array CGH analysis has also been employed in cancer gene identification. The clinical impact of FISH is pivotal, especially in the diagnosis, prognosis and treatment decisions for hematological diseases, all of which facilitate the practice of personalized medicine. This review summarizes the methodology and current utilization of these FISH techniques in unraveling chromosomal changes and highlights how the field is moving away from conventional methods towards molecular cytogenetics approaches. In addition, the potential of the more recently developed FISH tests in contributing information to genetic abnormalities is illustrated. (Chang Gung Med J 2012;35:96-110)

Serological response to mRNA and inactivated COVID-19 vaccine in healthcare workers in Hong Kong: preliminary results To the Editor-Healthcare workers (HCWs) in Hong Kong are among the priority groups to receive coronavirus disease 2019 (COVID-19) vaccination. We recruited HCWs who enrolled for COVID-19 vaccination from 22 February to 30 April 2021 for serial measurement of their anti-spike immunoglobulin M (IgM)/immunoglobulin G (IgG)/ total antibody and surrogate neutralising antibody using Abbott SARS-CoV-2 IgM/IgG II Quant assay; Roche Elecsys ® Anti-SARS-CoV-2 S, and GenScript cPass SARS-CoV-2 Surrogate Virus Neutralization Test Kit. The key exclusion criteria were history of polymerase chain reaction-confirmed COVID-19 or positive test for severe acute respiratory syndrome coronavirus 2-specific IgG or IgM in the serum. The

To the Editor-We previously reported serological findings of 302 healthcare workers (HCWs) who completed two doses of mRNA (BNT162b2/ Comirnaty;Fosun-BioNTech Pharma) and inactivated COVID-19 vaccine (CoronaVac; Sinovac Life Sciences, Beijing, China). 1 Both vaccines were found to be immunogenic in the majority of HCWs. The BNT162b2 resulted in a 11-fold higher level of anti-spike IgG (Abbott SARS-CoV-2 IgG II Quant assay, mean=11572.6 AU/mL vs 1005.2 AU/mL; P<0.001) and a higher surrogate neutralising antibody (sNAb) [GenScript cPass SARS-CoV-2 Surrogate Virus Neutralization Test Kit] positive rate (100% vs 94.4%; P<0.001).We report week 12 serological data of our cohort. Among 197 CoronaVac and 100 BNT162b2 recipients, baseline characteristics of the two