Strong association of human leukocyte antigen (HLA)-B*58:01 allele with allopurinol-induced hyper... more Strong association of human leukocyte antigen (HLA)-B*58:01 allele with allopurinol-induced hypersensitivity was found worldwide, especially in the Han Chinese populations. This study aims to develop and evaluate a loop-mediated isothermal amplification (LAMP) assay for rapid detection of HLA-B*58:01 . Two sets of LAMP primers targeting exons 2 and 3 of HLA-B*58:01 allele were designed and their annealing temperatures were optimized accordingly. The heating devices for LAMP assay were tested. The analytical sensitivities of the two sets of LAMP primers were determined by 1:10 serial dilution of a positive control with homozygous HLA-B*58:01 allele from 100 ng down to 1 fg. The analytical specificities of the LAMP primers were evaluated by 30 selected University of California, Los Angeles (UCLA) DNA Exchange Program samples with known HLA-B loci typings previously typed by sequencing. Both sets of LAMP primers targeting exons 2 and 3 amplified optimally at 67 • C. Thermal cycler is essential in achieving a more precise and specific LAMP result. The sensitivity of the exon 2 LAMP primer set was found to be 1 pg, whereas it was 10 ng for the exon 3 primer set in a 60-min amplification. The LAMP primers were highly specific because LAMP results were perfectly concordant to the sequencing results. The HLA-B*58:01 LAMP assay has compatible sensitivity and specificity to routine genotyping assays, and it is potentially an alternative screening test for the detection of HLA-B*58:01 and ultimately allopurinol-induced hypersensitivity.
A 5-year-old girl had poor growth and unresolving pneumonia. There was persistent collapse-consol... more A 5-year-old girl had poor growth and unresolving pneumonia. There was persistent collapse-consolidation of the right middle lobe. CT thorax revealed bilateral bronchial wall thickening and dilatation. Bronchoscopy showed numerous endobronchial mucosal nodules, consisting of dense lymphoid infiltrates. Bacterial culture of the nodule biopsy suggested endobronchial actinomycosis. She had T-cell lymphopenia. Genetic test confirmed the diagnosis of activated phosphatidylinositol 3-kinase delta syndrome (APDS), an immunodeficiency condition.
Background: Alloantibodies against human neutrophil antigens (HNA) are associated with a variety ... more Background: Alloantibodies against human neutrophil antigens (HNA) are associated with a variety of clinical conditions. Over the past decade, the allelic and genotypic frequencies of the five HNA systems have been evaluated. Although the HNA system is less polymorphic than human leukocyte antigens (HLA), significant differences in the genotypic and allele frequencies still exist in different populations, even those living in close proximity. Objectives: To delineate HNA genotypic and allele frequencies to provide vital information on estimating the risk of HNA-associated diseases for our local population. Methods: Using a validated, in-house-developed assay, genotyping for HNA-1, HNA-3, HLA-4 and HNA-5 was performed on 300 samples from Chinese blood donors from Hong Kong. In addition, the frequency of the HNA-2 c.843A > T allele was also determined. The allele frequencies of HNA-1a, -1b and -1c alleles were 67•8, 31•5 and 0%, respectively, whereas the frequencies of HNA-3a and HNA-3b were 71•0 and 29•0%, respectively. The frequencies of HNA-4a and -4b alleles were 99•5 and 0•5%, respectively, and for HNA-5a and -5b, alleles were 85•2 and 14•8%, respectively. Homozygotes for the HNA-2 c.843 TT variant were absent in our population, whereas only <4% of the population were c.843AT heterozygote carriers. Conclusions: This is the first study to define HNA genotype and allele frequencies using a validated modified in-house PCR-SSP method in the Hong Kong Chinese blood donor population. Our approach provides a cost-effective assay for conducting routine HNA typing and facilitates the incorporation of these assays into routine clinical service. Our results are comparable with those reported in the Guangzhou Chinese population, but the
Recent studies showed that ABO‐adjusted calculated panel reactive antibody (ABO‐cPRA) may better ... more Recent studies showed that ABO‐adjusted calculated panel reactive antibody (ABO‐cPRA) may better reflect the histocompatibility level in a multi‐ethnic population, but such data in Asians is not available. We developed an ABO‐adjusted cPRA metric on a cohort of waitlist kidney transplant patients (n = 647, 99% Chinese) in Hong Kong, based on HLA alleles and ABO frequencies of local donors. The concordance between the web‐based ABO‐cPRA calculator and the impact on kidney allocation were evaluated. The blood group distribution for A, B, O and AB among waitlist kidney candidates were 26.2%, 27.5%, 40.1%, and 6.1%, and their chances of encountering incompatible blood group donors were 32.6%, 32.4%, 57.6%, and 0%, respectively. There is poor agreement between web‐based ABO‐cPRA calculator and our locally developed metrics. Over 90% of patients showed an increase in cPRA after ABO adjustment, most notably in those with cPRA between 70% and 79%. Blood group O patients had a much greater i...
BackgroundWe previously reported inborn errors of TLR3- and TLR7-dependent type I interferon (IFN... more BackgroundWe previously reported inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity in 1-5% of unvaccinated patients with life-threatening COVID-19, and auto-antibodies against type I IFN in another 15-20% of cases.MethodsWe report here a genome-wide rare variant burden association analysis in 3,269 unvaccinated patients with life-threatening COVID-19 (1,301 previously reported and 1,968 new patients), and 1,373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. A quarter of the patients tested had antibodies against type I IFN (234 of 928) and were excluded from the analysis.ResultsNo gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants wasTLR7, with an OR of 27.68 (95%CI:1.5-528.7,P=1.1×10−4), in analyses restricted to biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-de...
To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions,... more To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions, our centre developed and offered free genetic testing for the most common IEI by Sanger sequencing (SS) since 2001. With the establishment of The Asian Primary Immunodeficiency (APID) Network in 2009, the awareness and definitive diagnosis of IEI were further improved with collaboration among centres caring for IEI patients from East and Southeast Asia. We also started to use whole exome sequencing (WES) for undiagnosed cases and further extended our collaboration with centres from South Asia and Africa. With the increased use of Next Generation Sequencing (NGS), we have shifted our diagnostic practice from SS to WES. However, SS was still one of the key diagnostic tools for IEI for the past two decades. Our centre has performed 2,024 IEI SS genetic tests, with in-house protocol designed specifically for 84 genes, in 1,376 patients with 744 identified to have disease-causing mutations (...
Background: Chronic benign neutropenia (CBN) and autoimmune neutropenia (AIN) are notoriously dif... more Background: Chronic benign neutropenia (CBN) and autoimmune neutropenia (AIN) are notoriously difficult to differentiate in children owing to their indistinguishable clinical course and varying availability and accuracy in the methods of anti-neutrophil antibody detection. This study aims to investigate whether the presence of anti-neutrophil antibody has implications on the disease course in Chinese children with AIN, as well as evaluating the various methods including LABScreen MULTI, granulocyte agglutination test (GAT) and granulocyte immunofluorescence test (GIFT) in anti-neutrophil antibody detection. Procedure: Chinese children under 18 years of age with neutropenia ≤ 1.5 x 109/L lasting 6 months or more in our single center were recruited into the study between 2016 to 2018. Patients with secondary causes of neutropenia were excluded. Blood for anti-neutrophil antibody and genotyping was taken once at the time of recruitment and subsequently when neutropenia recovered to ≥ 1...
Background Age-specific incidence of acute myocarditis/pericarditis in adolescents following Comi... more Background Age-specific incidence of acute myocarditis/pericarditis in adolescents following Comirnaty vaccination in Asia is lacking. This study aimed to study the clinical characteristics and incidence of acute myocarditis/pericarditis among Hong Kong adolescents following Comirnaty vaccination. Methods This is a population cohort study in Hong Kong that monitored adverse events following immunization through a pharmacovigilance system for coronavirus disease 2019 (COVID-19) vaccines. All adolescents aged between 12 and 17 years following Comirnaty vaccination were monitored under the COVID-19 vaccine adverse event response and evaluation program. The clinical characteristics and overall incidence of acute myocarditis/pericarditis in adolescents following Comirnaty vaccination were analyzed. Results Between 14 June 2021 and 4 September 2021, 33 Chinese adolescents who developed acute myocarditis/pericarditis following Comirnaty vaccination were identified. In total, 29 (87.88%) we...
Background and objectives: Donor helper T-lymphocytes may be involved in graft-versus-host diseas... more Background and objectives: Donor helper T-lymphocytes may be involved in graft-versus-host disease (GVHD) and a graft-versus-leukemia effect after bone marrow transplantation (BMT). We assayed donor helper T-lymphocyte precursor frequencies (HTLP(f)) to see whether they could predict the severity of GVHD and disease relapse after transplantation, thereby facilitating donor selection, pre-transplant counselling and modification of GVHD prophylaxis after BMT. Design and methods: Thirty-six consecutive adult BMT recipients and their HLA-identical sibling donors were recruited. HTLP((f)) was measured as a function of interleukin-2 secretion by alloreactive donor T-cells using a limiting dilution assay. Patients were followed prospectively to assess the severity of GVHD and the status of the primary disease after BMT. Results: Eight donors had HTLP((f)) less than or equal to 10(-6); no recipients of these grafts developed severe GVHD after transplantation. Twenty-eight donors had HTLP(f) greater than 10(-6) and 18 recipients of these grafts developed severe GVHD (> or = grade 2) (chi(2) test, p<0.01). Seven donors had HTLP(f) greater than 10(-5) and no recipient had disease relapse. Twenty-nine donors had HTLP(f) less than or equal to 10(-5), 11 recipients of these grafts developed disease relapse (chi(2) test, p=0.08). Interpretation and conclusions: BMT recipients from HLA-identical sibling donors with low (<10(-6)) and high (>10(-5)) HTLP(f) may have a low risk of acute GVHD and disease relapse after transplantation.
Background Allopurinol, a common medication for gout treatment, can cause rare but life-threateni... more Background Allopurinol, a common medication for gout treatment, can cause rare but life-threatening severe cutaneous adverse reactions. A strong pharmacogenetic association of human leucocyte antigen (HLA)-B*58:01 with allopurinol-induced drug hypersensitivity has been reported, especially in the Han Chinese population. Objectives To develop a rapid and simple loop-mediated isothermal amplification (LAMP) assay of HLA-B*58:01 and evaluate its feasibility in predicting allopurinol-induced drug hypersensitivity. Methods Two sets of LAMP primers targeting exons 2 and 3 of HLA-B*58:01 were designed. DNA extracted from 20 clinical blood samples of patients with gout was used to evaluate the effectiveness of the two LAMP primer sets for the detection of HLA-B*58:01. Results The results were compared with routine clinical genotyping methods. All extracted DNA samples tested with the HLA-B*58:01 LAMP assay showed agreement with the routine genotyping results. No amplifications were observed when unextracted blood samples were tested. Conclusions The HLA-B*58:01 LAMP assay was confirmed to be simple, rapid and specific for the detection of HLA-B*58:01, and therefore of potential value in the diagnosis of allopurinol-induced hypersensitivity.
Background: Human leukocyte antigen (HLA) selected platelets are frequently requested in patients... more Background: Human leukocyte antigen (HLA) selected platelets are frequently requested in patients with platelet transfusion refractoriness (PTR) due to HLA alloimmunization. A retrospective study was conducted to evaluate the provision of HLA-selected platelets by a regional blood centre from May 2010 to April 2020. Methods: In the study period, 1,080 units of HLA-selected platelets were collected from 393 donors recruited from the unrelated bone marrow donor registry. They were transfused to 147 patients (male 54%, mean age 48±21 years). Analysis was performed in each donor-recipient pair to identify the predictors of haematological response. Results: HLA-A and-B antigens in all except one donor-recipient pairs were 4 out of 4 matched. In 84% of instances, mean 1-hour corrected platelet count increment (CCI) were greater than 7,500 m 2 /µL, the threshold of satisfactory increment. Improvement in 1-hour CCI (CCI HLA selected platelets-CCI random donor platelets) of patients who were not refractory to random donor platelet transfusions was 11,134 m 2 /µL (95% CI: 12,326-14,306 m 2 /µL) less than those who had PTR. Following HLA-selected platelet transfusions, male patients' mean 1-hour CCI was 3,592 m 2 /µL (95% CI: 1270-7,145 m 2 /µL) less than that of female patients. Mean 1-hour CCI was 8,727 m 2 /µL (95% CI: 595-12,970 m 2 /µL) higher in patients who demonstrated anti-HLA antibodies. ABO compatibility did not significantly influence 1-hour CCI. Conclusions: HLA-selected platelets provided locally were almost exclusively 4 out of 4 matched and resulted in satisfactory 1-hour CCIs. In addition to expanding the donor pool, advocating judicious request for the product and thorough investigations of PTR could enhance service provision.
High resolution typing of the HLA-DPB1 locus for patient who requested for hematopoietic stem cel... more High resolution typing of the HLA-DPB1 locus for patient who requested for hematopoietic stem cell transplantation (HSCT) workup has recently become mandatory by the National Marrow Donor Program (NMDP) in order to facilitate matching between donors and recipients for better outcomes. The likelihood of identifying HLA matched donors in Hong Kong, on top of the existing HLA-A,-B,-C, and-DRB1 loci, is revisited in this study. HLA-A,-B,-C,-DRB1 and-DPB1 genotypes of 5,266 volunteer unrelated Chinese donors from the Hong Kong Bone Marrow Donor Registry (HKBMDR), were included in this study. Matching models were employed to determine the matching probabilities for 10/10(DPB1) and 9/10(DPB1) HLA match. The matching probabilities are 20% at 10/10(DPB1) HLA match and 55% at 9/10(DPB1) match, based on the existing 130,000 donors in the HKBMDR. The likelihoods of match become 27% and 65% respectively, by increasing the registry to 250,000. However, if DPB T-cell-epitope (TCE) model is considered in the matching, the probability will increase to 46% at 10/10 DPB1 permissive mismatching. Our findings provide vital information about the future planning on the targeted recruitment size, HLA typing and search strategies of the donor registry and arose the transplant physicians' acceptability to 9/ 10(DBP1) or 10/10(DBP1) HLA match. Nevertheless, the marrow donor registry has planned for increasing the registry size and bringing down the age of recruited donors which will ultimately enhance patient outcome.
Strong association of human leukocyte antigen (HLA)-B*58:01 allele with allopurinol-induced hyper... more Strong association of human leukocyte antigen (HLA)-B*58:01 allele with allopurinol-induced hypersensitivity was found worldwide, especially in the Han Chinese populations. This study aims to develop and evaluate a loop-mediated isothermal amplification (LAMP) assay for rapid detection of HLA-B*58:01 . Two sets of LAMP primers targeting exons 2 and 3 of HLA-B*58:01 allele were designed and their annealing temperatures were optimized accordingly. The heating devices for LAMP assay were tested. The analytical sensitivities of the two sets of LAMP primers were determined by 1:10 serial dilution of a positive control with homozygous HLA-B*58:01 allele from 100 ng down to 1 fg. The analytical specificities of the LAMP primers were evaluated by 30 selected University of California, Los Angeles (UCLA) DNA Exchange Program samples with known HLA-B loci typings previously typed by sequencing. Both sets of LAMP primers targeting exons 2 and 3 amplified optimally at 67 • C. Thermal cycler is essential in achieving a more precise and specific LAMP result. The sensitivity of the exon 2 LAMP primer set was found to be 1 pg, whereas it was 10 ng for the exon 3 primer set in a 60-min amplification. The LAMP primers were highly specific because LAMP results were perfectly concordant to the sequencing results. The HLA-B*58:01 LAMP assay has compatible sensitivity and specificity to routine genotyping assays, and it is potentially an alternative screening test for the detection of HLA-B*58:01 and ultimately allopurinol-induced hypersensitivity.
A 5-year-old girl had poor growth and unresolving pneumonia. There was persistent collapse-consol... more A 5-year-old girl had poor growth and unresolving pneumonia. There was persistent collapse-consolidation of the right middle lobe. CT thorax revealed bilateral bronchial wall thickening and dilatation. Bronchoscopy showed numerous endobronchial mucosal nodules, consisting of dense lymphoid infiltrates. Bacterial culture of the nodule biopsy suggested endobronchial actinomycosis. She had T-cell lymphopenia. Genetic test confirmed the diagnosis of activated phosphatidylinositol 3-kinase delta syndrome (APDS), an immunodeficiency condition.
Background: Alloantibodies against human neutrophil antigens (HNA) are associated with a variety ... more Background: Alloantibodies against human neutrophil antigens (HNA) are associated with a variety of clinical conditions. Over the past decade, the allelic and genotypic frequencies of the five HNA systems have been evaluated. Although the HNA system is less polymorphic than human leukocyte antigens (HLA), significant differences in the genotypic and allele frequencies still exist in different populations, even those living in close proximity. Objectives: To delineate HNA genotypic and allele frequencies to provide vital information on estimating the risk of HNA-associated diseases for our local population. Methods: Using a validated, in-house-developed assay, genotyping for HNA-1, HNA-3, HLA-4 and HNA-5 was performed on 300 samples from Chinese blood donors from Hong Kong. In addition, the frequency of the HNA-2 c.843A > T allele was also determined. The allele frequencies of HNA-1a, -1b and -1c alleles were 67•8, 31•5 and 0%, respectively, whereas the frequencies of HNA-3a and HNA-3b were 71•0 and 29•0%, respectively. The frequencies of HNA-4a and -4b alleles were 99•5 and 0•5%, respectively, and for HNA-5a and -5b, alleles were 85•2 and 14•8%, respectively. Homozygotes for the HNA-2 c.843 TT variant were absent in our population, whereas only <4% of the population were c.843AT heterozygote carriers. Conclusions: This is the first study to define HNA genotype and allele frequencies using a validated modified in-house PCR-SSP method in the Hong Kong Chinese blood donor population. Our approach provides a cost-effective assay for conducting routine HNA typing and facilitates the incorporation of these assays into routine clinical service. Our results are comparable with those reported in the Guangzhou Chinese population, but the
Recent studies showed that ABO‐adjusted calculated panel reactive antibody (ABO‐cPRA) may better ... more Recent studies showed that ABO‐adjusted calculated panel reactive antibody (ABO‐cPRA) may better reflect the histocompatibility level in a multi‐ethnic population, but such data in Asians is not available. We developed an ABO‐adjusted cPRA metric on a cohort of waitlist kidney transplant patients (n = 647, 99% Chinese) in Hong Kong, based on HLA alleles and ABO frequencies of local donors. The concordance between the web‐based ABO‐cPRA calculator and the impact on kidney allocation were evaluated. The blood group distribution for A, B, O and AB among waitlist kidney candidates were 26.2%, 27.5%, 40.1%, and 6.1%, and their chances of encountering incompatible blood group donors were 32.6%, 32.4%, 57.6%, and 0%, respectively. There is poor agreement between web‐based ABO‐cPRA calculator and our locally developed metrics. Over 90% of patients showed an increase in cPRA after ABO adjustment, most notably in those with cPRA between 70% and 79%. Blood group O patients had a much greater i...
BackgroundWe previously reported inborn errors of TLR3- and TLR7-dependent type I interferon (IFN... more BackgroundWe previously reported inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity in 1-5% of unvaccinated patients with life-threatening COVID-19, and auto-antibodies against type I IFN in another 15-20% of cases.MethodsWe report here a genome-wide rare variant burden association analysis in 3,269 unvaccinated patients with life-threatening COVID-19 (1,301 previously reported and 1,968 new patients), and 1,373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. A quarter of the patients tested had antibodies against type I IFN (234 of 928) and were excluded from the analysis.ResultsNo gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants wasTLR7, with an OR of 27.68 (95%CI:1.5-528.7,P=1.1×10−4), in analyses restricted to biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-de...
To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions,... more To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions, our centre developed and offered free genetic testing for the most common IEI by Sanger sequencing (SS) since 2001. With the establishment of The Asian Primary Immunodeficiency (APID) Network in 2009, the awareness and definitive diagnosis of IEI were further improved with collaboration among centres caring for IEI patients from East and Southeast Asia. We also started to use whole exome sequencing (WES) for undiagnosed cases and further extended our collaboration with centres from South Asia and Africa. With the increased use of Next Generation Sequencing (NGS), we have shifted our diagnostic practice from SS to WES. However, SS was still one of the key diagnostic tools for IEI for the past two decades. Our centre has performed 2,024 IEI SS genetic tests, with in-house protocol designed specifically for 84 genes, in 1,376 patients with 744 identified to have disease-causing mutations (...
Background: Chronic benign neutropenia (CBN) and autoimmune neutropenia (AIN) are notoriously dif... more Background: Chronic benign neutropenia (CBN) and autoimmune neutropenia (AIN) are notoriously difficult to differentiate in children owing to their indistinguishable clinical course and varying availability and accuracy in the methods of anti-neutrophil antibody detection. This study aims to investigate whether the presence of anti-neutrophil antibody has implications on the disease course in Chinese children with AIN, as well as evaluating the various methods including LABScreen MULTI, granulocyte agglutination test (GAT) and granulocyte immunofluorescence test (GIFT) in anti-neutrophil antibody detection. Procedure: Chinese children under 18 years of age with neutropenia ≤ 1.5 x 109/L lasting 6 months or more in our single center were recruited into the study between 2016 to 2018. Patients with secondary causes of neutropenia were excluded. Blood for anti-neutrophil antibody and genotyping was taken once at the time of recruitment and subsequently when neutropenia recovered to ≥ 1...
Background Age-specific incidence of acute myocarditis/pericarditis in adolescents following Comi... more Background Age-specific incidence of acute myocarditis/pericarditis in adolescents following Comirnaty vaccination in Asia is lacking. This study aimed to study the clinical characteristics and incidence of acute myocarditis/pericarditis among Hong Kong adolescents following Comirnaty vaccination. Methods This is a population cohort study in Hong Kong that monitored adverse events following immunization through a pharmacovigilance system for coronavirus disease 2019 (COVID-19) vaccines. All adolescents aged between 12 and 17 years following Comirnaty vaccination were monitored under the COVID-19 vaccine adverse event response and evaluation program. The clinical characteristics and overall incidence of acute myocarditis/pericarditis in adolescents following Comirnaty vaccination were analyzed. Results Between 14 June 2021 and 4 September 2021, 33 Chinese adolescents who developed acute myocarditis/pericarditis following Comirnaty vaccination were identified. In total, 29 (87.88%) we...
Background and objectives: Donor helper T-lymphocytes may be involved in graft-versus-host diseas... more Background and objectives: Donor helper T-lymphocytes may be involved in graft-versus-host disease (GVHD) and a graft-versus-leukemia effect after bone marrow transplantation (BMT). We assayed donor helper T-lymphocyte precursor frequencies (HTLP(f)) to see whether they could predict the severity of GVHD and disease relapse after transplantation, thereby facilitating donor selection, pre-transplant counselling and modification of GVHD prophylaxis after BMT. Design and methods: Thirty-six consecutive adult BMT recipients and their HLA-identical sibling donors were recruited. HTLP((f)) was measured as a function of interleukin-2 secretion by alloreactive donor T-cells using a limiting dilution assay. Patients were followed prospectively to assess the severity of GVHD and the status of the primary disease after BMT. Results: Eight donors had HTLP((f)) less than or equal to 10(-6); no recipients of these grafts developed severe GVHD after transplantation. Twenty-eight donors had HTLP(f) greater than 10(-6) and 18 recipients of these grafts developed severe GVHD (> or = grade 2) (chi(2) test, p<0.01). Seven donors had HTLP(f) greater than 10(-5) and no recipient had disease relapse. Twenty-nine donors had HTLP(f) less than or equal to 10(-5), 11 recipients of these grafts developed disease relapse (chi(2) test, p=0.08). Interpretation and conclusions: BMT recipients from HLA-identical sibling donors with low (<10(-6)) and high (>10(-5)) HTLP(f) may have a low risk of acute GVHD and disease relapse after transplantation.
Background Allopurinol, a common medication for gout treatment, can cause rare but life-threateni... more Background Allopurinol, a common medication for gout treatment, can cause rare but life-threatening severe cutaneous adverse reactions. A strong pharmacogenetic association of human leucocyte antigen (HLA)-B*58:01 with allopurinol-induced drug hypersensitivity has been reported, especially in the Han Chinese population. Objectives To develop a rapid and simple loop-mediated isothermal amplification (LAMP) assay of HLA-B*58:01 and evaluate its feasibility in predicting allopurinol-induced drug hypersensitivity. Methods Two sets of LAMP primers targeting exons 2 and 3 of HLA-B*58:01 were designed. DNA extracted from 20 clinical blood samples of patients with gout was used to evaluate the effectiveness of the two LAMP primer sets for the detection of HLA-B*58:01. Results The results were compared with routine clinical genotyping methods. All extracted DNA samples tested with the HLA-B*58:01 LAMP assay showed agreement with the routine genotyping results. No amplifications were observed when unextracted blood samples were tested. Conclusions The HLA-B*58:01 LAMP assay was confirmed to be simple, rapid and specific for the detection of HLA-B*58:01, and therefore of potential value in the diagnosis of allopurinol-induced hypersensitivity.
Background: Human leukocyte antigen (HLA) selected platelets are frequently requested in patients... more Background: Human leukocyte antigen (HLA) selected platelets are frequently requested in patients with platelet transfusion refractoriness (PTR) due to HLA alloimmunization. A retrospective study was conducted to evaluate the provision of HLA-selected platelets by a regional blood centre from May 2010 to April 2020. Methods: In the study period, 1,080 units of HLA-selected platelets were collected from 393 donors recruited from the unrelated bone marrow donor registry. They were transfused to 147 patients (male 54%, mean age 48±21 years). Analysis was performed in each donor-recipient pair to identify the predictors of haematological response. Results: HLA-A and-B antigens in all except one donor-recipient pairs were 4 out of 4 matched. In 84% of instances, mean 1-hour corrected platelet count increment (CCI) were greater than 7,500 m 2 /µL, the threshold of satisfactory increment. Improvement in 1-hour CCI (CCI HLA selected platelets-CCI random donor platelets) of patients who were not refractory to random donor platelet transfusions was 11,134 m 2 /µL (95% CI: 12,326-14,306 m 2 /µL) less than those who had PTR. Following HLA-selected platelet transfusions, male patients' mean 1-hour CCI was 3,592 m 2 /µL (95% CI: 1270-7,145 m 2 /µL) less than that of female patients. Mean 1-hour CCI was 8,727 m 2 /µL (95% CI: 595-12,970 m 2 /µL) higher in patients who demonstrated anti-HLA antibodies. ABO compatibility did not significantly influence 1-hour CCI. Conclusions: HLA-selected platelets provided locally were almost exclusively 4 out of 4 matched and resulted in satisfactory 1-hour CCIs. In addition to expanding the donor pool, advocating judicious request for the product and thorough investigations of PTR could enhance service provision.
High resolution typing of the HLA-DPB1 locus for patient who requested for hematopoietic stem cel... more High resolution typing of the HLA-DPB1 locus for patient who requested for hematopoietic stem cell transplantation (HSCT) workup has recently become mandatory by the National Marrow Donor Program (NMDP) in order to facilitate matching between donors and recipients for better outcomes. The likelihood of identifying HLA matched donors in Hong Kong, on top of the existing HLA-A,-B,-C, and-DRB1 loci, is revisited in this study. HLA-A,-B,-C,-DRB1 and-DPB1 genotypes of 5,266 volunteer unrelated Chinese donors from the Hong Kong Bone Marrow Donor Registry (HKBMDR), were included in this study. Matching models were employed to determine the matching probabilities for 10/10(DPB1) and 9/10(DPB1) HLA match. The matching probabilities are 20% at 10/10(DPB1) HLA match and 55% at 9/10(DPB1) match, based on the existing 130,000 donors in the HKBMDR. The likelihoods of match become 27% and 65% respectively, by increasing the registry to 250,000. However, if DPB T-cell-epitope (TCE) model is considered in the matching, the probability will increase to 46% at 10/10 DPB1 permissive mismatching. Our findings provide vital information about the future planning on the targeted recruitment size, HLA typing and search strategies of the donor registry and arose the transplant physicians' acceptability to 9/ 10(DBP1) or 10/10(DBP1) HLA match. Nevertheless, the marrow donor registry has planned for increasing the registry size and bringing down the age of recruited donors which will ultimately enhance patient outcome.
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Papers by Janette Kwok