Changing Epidemiology of Pathogenic Bacteria Over the Past 20 Years in Korea

Background@#The epidemiology of pathogenic bacteria varies according to the socioeconomic status and antimicrobial resistance status. However, longitudinal epidemiological studies to evaluate the changes in species distribution and antimicrobial susceptibility of pathogenic bacteria nationwide are lacking. We retrospectively investigated the nationwide trends in species distribution and antimicrobial susceptibility of pathogenic bacteria over the last 20 years in Korea. @*Methods@#From 1997 to 2016, annual cumulative antimicrobial susceptibility and species distribution data were collected from 12 university hospitals in five provinces and four metropolitan cities in South Korea. @*Results@#The prevalence of Staphylococcus aureus was the highest (13.1%) until 2012 but decreased to 10.3% in 2016, consistent with the decrease in oxacillin resistance from 76.1% in 2008 to 62.5% in 2016. While the cefotaxime resistance of Escherichia coli increased from 9.0% in 1997 to 34.2% in 2016, E. coli became the most common species since 2013, accounting for 14.5% of all isolates in 2016. Pseudomonas aeruginosa and Acinetobacter baumannii rose to third and fifth places in 2008 and 2010, respectively, while imipenem resistance increased from 13.9% to 30.8% and 0.7% to 73.5% during the study period, respectively.Streptococcus agalactiae became the most common pathogenic streptococcal species in 2016, as the prevalence of Streptococcus pneumoniae decreased since 2010. During the same period, pneumococcal penicillin susceptibility decreased to 79.0%, and levofloxacin susceptibility of S. agalactiae decreased to 77.1% in 2016. @*Conclusion@#The epidemiology of pathogenic bacteria has changed significantly over the past 20 years according to trends in antimicrobial resistance in Korea. Efforts to confine antimicrobial resistance would change the epidemiology of pathogenic bacteria and, consequently, the diagnosis and treatment of infectious diseases.

Effect of Wearing Personal Protective Equipment (PPE) for COVID-19Treatment on Blood Culture Contamination: Implication for Optimal PPE Strategies

The personal protective equipment (PPE) used to minimize exposure to hazards can hinder healthcare workers from performing sophisticated procedures. We retrospectively reviewed 77,535 blood cultures (202,012 pairs) performed in 28,502 patients from January 2020 to April 2022. The contamination rate of all blood cultures was significantly elevated in the coronavirus disease 2019 ward at 4.68%, compared to intensive care units at 2.56%, emergency rooms at 1.13%, hematology wards at 1.08%, and general wards at 1.07% (All of P < 0.001). This finding implies that wearing PPE might interfere with adherence to the aseptic technique. Therefore, a new PPE policy is needed that considers the balance between protecting healthcare workers and medical practices.

Evaluation of Three Multiplex Realtime Reverse Transcription PCR Assays for Simultaneous Detection of SARS-CoV-2, Influenza A/B, and Respiratory Syncytial Virus in Nasopharyngeal Swabs

Background@#In the coronavirus disease 2019 (COVID-19) pandemic era, the simultaneous detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza virus (Flu), and respiratory syncytial virus (RSV) is important in the rapid differential diagnosis in patients with respiratory symptoms. Three multiplex real-time reverse transcription polymerase chain reaction (rRT-PCR) assays have been recently developed commercially in Korea: PowerChek™ SARS-CoV-2, Influenza A&B Multiplex Real-time PCR Kit (PowerChek; KogeneBiotech); STANDARD™ M Flu/SARS-CoV-2 Real-time Detection Kit (STANDARD M; SD BioSensor); and Allplex™ SARS-CoV-2/FluA/FluB/RSV Assay (Allplex; Seegene). We evaluated the analytical and clinical performances of these kits. @*Methods@#A limit of detection tests were performed and cross-reactivity analysis was executed using clinical respiratory samples. Ninety-seven SARS-CoV-2-positive, 201 SARS-CoV-2-negative, 71 influenza A-positive, 50 influenza B-positive, 78 RSV-positive, and 207 other respiratory virus-positive nasopharyngeal swabs were tested using the three assays. The AdvanSure™ respiratory viruses rRT-PCR assay (AdvanSure; LG Life Sciences) was used as a comparator assay for RSV. @*Results@#Except in influenza B, in SARS-CoV-2 and influenza A, there were no significant differences in detecting specific genes of the viruses among the three assays. All three kits did not cross-react with common respiratory viruses. All three kits had greater than 92% positive percent agreement and negative percent agreement and ≥ 0.95 kappa value in the detection of SARS-CoV-2 and flu A/B. Allplex detected RSV more sensitively than AdvanSure. @*Conclusion@#The overall performance of three multiplex rRT-PCR assays for the concurrent detection of SARS-CoV-2, influenza A/B, and RSV was comparable. These kits will promote prompt differential diagnosis of COVID-19, influenza, and RSV infection in the COVID-19 pandemic era.

A Direct Rapid Phenotypic Antimicrobial Susceptibility Test Enables Early Selection of Optimal Antibiotics to Treat Bacteremia in COVID-19 Patients

Background@#Co-infection with bacteria and severe acute respiratory syndrome coronavirus 2 may result in greater use of healthcare resources and a poor prognosis. Therefore, early selection and use of optimal antibiotics are essential. The direct rapid antibiotic susceptibility test (dRAST) can detect antibiotic resistance within 6 h of a Gram smear result. This study aimed to assess the effectiveness of dRAST for improving early selection of appropriate antibiotics for coronavirus disease 2019 (COVID-19) patients with bacteremia. @*Materials and Methods@#This retrospective study included 96 blood culture-positive COVID-19 patients. Bacterial isolates and antimicrobial resistance profiles of each case were evaluated. Cases were divided into two groups based on whether they underwent conventional antibiotic susceptibility test (AST) or dRAST. The time to optimal targeted treatment for the two groups was investigated and compared. In addition, we examined the proportion of cases for which appropriate antibiotics were selected and broad spectrum antibiotics were administered at 72 h from blood sample collection. @*Results@#The mean time to optimal targeted antibiotic treatment was shorter for the dRAST group [55.7; standard deviation (SD), 28.7 vs. 92.3; SD, 51.1 h; P = 0.041]. The proportion of cases receiving optimal targeted antibiotics 72 h after blood collection for culture was higher [6/10 (60.0%) vs. 10/25 (40.0%)] and the percentage receiving broad spectrum antibiotics at 72 h was lower [6/10 (60.0%) vs. 19/25 (76.0%)] in the dRAST group than in the conventional AST group. In terms of microbiology profile, the contamination rate was high (35.5%) and multidrug-resistant strains were common (63.2%) in COVID-19 patients with bacteremia. @*Conclusion@#Application of dRAST for selection of antibiotics to treat bacteremia in COVID-19 patients may enable earlier and optimal treatment. The high incidence of contamination and resistant organisms in blood cultures from COVID-19 patients suggest that dRAST may speed up appropriate targeted treatment.

Clinical Application of the Standard Q COVID-19 Ag Test for the Detection of SARS-CoV-2 Infection

We evaluated the Standard Q COVID-19 Ag test for the diagnosis of coronavirus disease 2019 (COVID-19) compared to the reverse transcription-polymerase chain reaction (RT-PCR) test.We applied both tests to patients who were about to be hospitalized, had visited an emergency room, or had been admitted due to COVID-19 confirmed by RT-PCR. Two nasopharyngeal swabs were obtained; one was tested by RT-PCR and the other by the Standard Q COVID-19 Ag test. A total of 118 pairs of tests from 98 patients were performed between January 5 and 11, 2021. The overall sensitivity and specificity for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for the Standard Q COVID-19 Ag test compared to RT-PCR were 17.5% (95% confidence interval [CI], 8.8–32.0%) and 100% (95% CI, 95.3–100.0%). Analysis of the results using RT-PCR cycle thresholds of ≤ 30 or ≤ 25 increased the sensitivity to 26.9% (95% CI, 13.7–46.1%), and 41.1% (95% CI, 21.6–64.0%), respectively.

Clinical Application of the Standard Q COVID-19 Ag Test for the Detection of SARS-CoV-2 Infection

We evaluated the Standard Q COVID-19 Ag test for the diagnosis of coronavirus disease 2019 (COVID-19) compared to the reverse transcription-polymerase chain reaction (RT-PCR) test.We applied both tests to patients who were about to be hospitalized, had visited an emergency room, or had been admitted due to COVID-19 confirmed by RT-PCR. Two nasopharyngeal swabs were obtained; one was tested by RT-PCR and the other by the Standard Q COVID-19 Ag test. A total of 118 pairs of tests from 98 patients were performed between January 5 and 11, 2021. The overall sensitivity and specificity for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for the Standard Q COVID-19 Ag test compared to RT-PCR were 17.5% (95% confidence interval [CI], 8.8–32.0%) and 100% (95% CI, 95.3–100.0%). Analysis of the results using RT-PCR cycle thresholds of ≤ 30 or ≤ 25 increased the sensitivity to 26.9% (95% CI, 13.7–46.1%), and 41.1% (95% CI, 21.6–64.0%), respectively.

Surveillance of Coronavirus Disease 2019 (COVID-19) Testing in Clinical Laboratories in Korea

In response to the ongoing coronavirus disease 2019 (COVID-19) pandemic, an online laboratory surveillance system was established to monitor severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) real-time reverse transcription-PCR (rRT-PCR) testing capacities and results. SARS-CoV-2 rRT-PCR testing data were collected from 97 clinical laboratories, including 84 medical institutions and 13 independent clinical laboratories in Korea. We assessed the testing capacities to utilize SARS-CoV-2 rRT-PCR based on surveillance data obtained from February 7th to June 4th, 2020 and evaluated positive result characteristics according to the reagents used and sample types. A total of 1,890,319 SARS-CoV-2 rRT-PCR testing were performed, 2.3% of which were positive. Strong correlations were observed between the envelope (E ) gene and RNA-dependent RNA polymerase (RdRp )ucleocapsid (N ) genes threshold cycle (Ct) values for each reagent. No statistically significant differences in gene Ct values were observed between the paired upper and lower respiratory tract samples, except in the N gene for nasopharyngeal swab and sputum samples. Our study showed that clinical laboratories in Korea have rapidly expanded their testing capacities in response to the COVID-19 outbreak, with a peak daily capacity of 34,193 tests. Rapid expansion in testing capacity is a critical component of the national response to the ongoing pandemic.

In vitro activity of lopinavir/ritonavir and hydroxychloroquine against severe acute respiratory syndrome coronavirus 2 at concentrations achievable by usual doses

Background/Aims@#As the coronavirus disease-2019 global pandemic progresses, screening of antiviral agents effective against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is urgently needed. In addition, considering the viral load kinetics of SARS-CoV-2, which peaks early in the illness, and the massive burden of the disease, which may increase in the near future, identifying well-tolerated oral antivirals becomes increasingly important. We examined the in vitro activity of lopinavir/ritonavir and hydroxychloroquine on SARS-CoV-2, at concentrations which can be used to treat coronavirus-19 patients with little concern of toxicity. @*Methods@#Lopinavir/ritonavir (7/1.75 μg/mL), hydroxychloroquine base (1 or 2 μg/mL), or a combination thereof were administered 1 hour after the inoculation of SARS-CoV-2 to Vero cells at a multiplicity of infection of 0.05. We examined cytopathic effects of virus 48 hours after administration of the respective treatments and measured viral loads at three time points (0, 24, and 48 hours post-treatment) by quantitative real-time reverse-transcription polymerase chain reaction, and compared the results obtained from the different antiviral regimens tested. @*Results@#The severity of cytopathic effects was lower in lopinavir/ritonavir-treated cells, and viral load was significantly reduced in this group compared with the control group (p < 0.001). However, hydroxychloroquine did not show significant inhibitory effects on anti-SARS-CoV-2-mediated cytotoxicity or on viral load at either concentration. @*Conclusions@#Lopinavir/ritonavir showed significant inhibitory effects on SARS-CoV-2 in vitro at its usual plasma concentration. However, the in vitro antiviral activity of hydroxychloroquine at concentrations commonly used in humans was minimal, whether used alone or in combination with lopinavir/ritonavir.

Guidelines for Laboratory Diagnosis of Coronavirus Disease 2019 (COVID-19) in Korea

The outbreak of coronavirus disease 2019 (COVID-19), which began in December 2019, is still ongoing in Korea, with >9,000 confirmed cases as of March 25, 2020. COVID-19 is a severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) infection, and real-time reverse transcription-PCR is currently the most reliable diagnostic method for COVID-19 around the world. Korean Society for Laboratory Medicine and the Korea Centers for Disease Prevention and Control propose guidelines for diagnosing COVID-19 in clinical laboratories in Korea. These guidelines are based on other related domestic and international guidelines, as well as expert opinions and include the selection of test subjects, selection of specimens, diagnostic methods, interpretation of test results, and biosafety.

A Case of Fungemia with Co-isolation of Candida parapsilosis and Trichosporon asahii Confirmed by MALDI-TOF MS and D2 rRNA Sequencing

Fungi are a major cause of human infections with diverse clinical manifestations. The incidence of fungal infections has increased over time, particularly in patients who have risk factors such as neutropenia, immune suppression, an intravascular catheter, parenteral nutrition, a prosthetic device, and prior broad spectrum antibiotic therapy. Here, we present an unusual case of co-infection by 2 distinct fungi, Candida parapsilosis and Trichosporon asahii, isolated from a patient who did not have any known risk factors initially, except active pulmonary tuberculosis. Despite the negative conversion of sputum acid-fast bacilli (AFB) culture test after treatment, clinical symptoms were refractory to therapy. The patient developed symptoms suggesting septic shock, and 2 distinct colonies were isolated from a blood specimen, which were identified as C. parapsilosis and T. asahii by MALDI-TOF and rRNA sequencing. Fever and hypotension were relieved after anti-fungal agent injection, and pulmonary lesions identified by imaging also improved.

Correction: Clinical Evaluation of QMAC-dRAST for Direct and Rapid Antimicrobial Susceptibility Test with Gram-Positive Cocci from Positive Blood Culture Bottles / 대한임상미생물학회지

There was an error in the article, the names of manufacturers and countries of equipments in the Korean abstract were reversed.

Clinical Evaluation of QMAC-dRAST for Direct and Rapid Antimicrobial Susceptibility Test with Gram-Positive Cocci from Positive Blood Culture Bottles / 대한임상미생물학회지

BACKGROUND: Timely intervention in the treatment of bloodstream infection is important for prescription of appropriate antimicrobials. With prompt determination of the antimicrobial susceptibility of a causative agent, rapid antimicrobial susceptibility test (AST) can help select the appropriate antimicrobial therapy. This clinical study is for evaluation of the clinical performance of the QMAC-dRAST for rapid AST directly from positive blood culture (PBC)s with Gram-positive cocci. METHODS: A total of 115 PBC samples with Gram-positive organisms (76 Staphylococcus spp. and 39 Enterococcus spp.) were evaluated by the QMAC-dRAST system, and their pure culture isolates were evaluated by the MicroScan WalkAway (Beckman Coulter, USA) as the comparative AST system. Thirteen antimicrobial agents were included, and the agreement and discrepancy rates of the QMAC-dRAST system (Quantamatrix Inc., Republic of Korea) compared to the MicroScan WalkAway were calculated. To resolve discrepancies, the broth microdilution method was performed. RESULTS: The QMAC-dRAST system exhibited a categorical agreement rate of 94.9% (1,126/1,187) and an essential agreement rate of 98.3% (1,167/1,187). The QMAC-dRAST system yielded very major (false-susceptible) errors at 1.0% (5/485), major (false-resistant) errors at 1.3% (9/693), and minor errors at 4.0% (47/1,187) compared to the MicroScan WalkAway. The QMAC-dRAST system significantly eliminated 30 hours of total turnaround time by combination of direct inoculation of PBC and an image-based approach. CONCLUSION: The results of the QMAC-dRAST system were highly accurate. Thereby, the QMAC-dRAST may provide essential information to accelerate therapeutic decisions for earlier and adequate antibiotic treatment and patient management in clinical settings.

Strategies to Prevent Transfusion-Transmitted Infection in Blood Centers / 대한수혈학회지

There has been continuous effort to prevent transfusion-transmitted infection (TTI). Strategies to prevent TTI can be divided into two components: first, determining donor eligibility, and second, managing bacterial contamination of blood products. To determine donor eligibility, medical history taking and screening tests for infectious diseases should be performed. To prevent bacterial contamination, blood collection process should be aseptic, tests for bacterial detection should be performed, and an application of pathogen reduction technology should also be considered. In this review, screening test items and methods, including nucleic acid amplification tests for determining donor eligibility, and precautions for blood collection, bacterial detection methods, and pathogen reduction technology for the prevention of bacterial contamination of blood products were discussed in detail.

External Quality Assessment of MERS-CoV Molecular Diagnostics During the 2015 Korean Outbreak

BACKGROUND: The largest outbreak of Middle East respiratory syndrome coronavirus (MERS-CoV) infection outside Middle East Asia in 2015 has necessitated the rapid expansion of laboratories that conduct MERS-CoV molecular testing in Korea, together with external quality assessment (EQA) to evaluate the assays used. METHODS: The EQA program consisted of two phases; self-validation and blind assessment. For the first EQA phase, in vitro transcribed upstream region of the envelope gene (upE) and the open reading frame (ORF)1a RNAs were used at a concentration of 1,000 copies/microL. The test panel for the second EQA phase consisted of RNA extracts from three samples, which were obtained from two MERS-CoV positive patients and one MERS-CoV negative patient. RESULTS: The first EQA phase results for 46 participants showed a linear relationship between the threshold cycle (CT) values of RNA materials and the logarithmic concentrations for both upE and ORF1a gene targets (R2=0.73 and 0.75, respectively). The mean CT value for each concentration was different depending on which commercial kit was used for the assay. Among the three commonly used kits, PowerChek MERS Real-Time PCR kit (KogeneBiotech, Korea) showed the lowest CT values at all concentrations of upE and most concentrations of ORF1a. The second EQA phase results for 47 participants were 100% correct for all tested samples. CONCLUSIONS: This EQA survey demonstrates that the MERS-CoV molecular testing performed in Korea during the 2015 outbreak is of robust capability. However, careful establishment and validation of a cut-off value are recommended to ensure good analytical sensitivity.

Flavobacterium ceti From Blood Samples of a Korean Patient With Alcoholic Liver Cirrhosis

No abstract available.

MALDI-TOF MS: Its Application in the Clinical Laboratory and a Paradigm Shift in Clinical Microbiology

In the past decade, clinical microbiology underwent revolutionary changes in methods used to identify microorganisms, a transition from slow and traditional microbial identification algorithms to rapid molecular methods and mass spectrometry (MS). Earlier, MS was clinically used as a highly complex method that was adapted for protein-centered analysis of samples in chemistry laboratories. Recently, a paradigm-shift happened when matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) MS was implemented to be used in microbiology laboratories for rapid and robust methods for accurate microbial identification. Two instrument platforms, marketed by well-established manufacturers, are beginning to displace automated phenotypic identification instruments and in some cases even genetic sequence-based identification practices. This review summarizes the current role of MALDI-TOF MS in clinical research, in diagnostic clinical microbiology laboratories, and serves as an introduction to MALDI-TOF MS, highlighting research associated with sample preparation, algorithms, interpretations, and limitations. Currently available MALDI-TOF MS instruments as well as software platforms that support the use of MALDI-TOF with direct specimens have been discussed in this review. Finally, clinical laboratories are consistently striving to extend the potential of these new methods, often in partnership with developmental scientists, resulting in novel technologies, such as MALDI-TOF MS, which could shape and define the diagnostic landscape for years to come.

Frequency of CD36 Deficiency on Platelets and Monocytes in Koreans / 대한수혈학회지

BACKGROUND: CD36 deficiency was first identified in a patient who showed refractoriness to HLA-matched platelet transfusion. CD36 deficiency can be divided into two subgroups. The type I phenotype is characterized by platelets and monocytes exhibiting CD36 deficiency. The type II phenotype lacks surface expression of CD36 in platelets only. In this study, the frequency of type I and type II CD36 deficiency in Koreans was evaluated. METHODS: A total of 220 samples were randomly selected from subjects who requested CBC testing from August 2013 to February 2014. The expression levels of CD36 on platelets and monocytes were analyzed by flow cytometry using FITC-conjugated CD36 antibodies. Correlation between the median fluorescence intensity of CD36 and the number of platelets or monocytes was evaluated using Pearson's correlation coefficient. RESULTS: Type I phenotype, lacking CD36 on platelets and monocytes, was present in 0.9% and type II, lacking CD36 on platelets, was present in 3.2%. The median fluorescence intensity of CD36 did not show correlation with the count of platelets or monocytes. CONCLUSION: Type I subjects may produce alloantibodies against CD36 following transfusion or pregnancy, leading to refractoriness to HLA-matched platelet transfusion, post-transfusion purpura, or neonatal immune thrombocytopenia. Studies to determine exact frequency of CD36 deficiency in Koreans, including a larger population, should be conducted, and more case reports on patients immunized against CD36 are also needed in order to elucidate the clinical importance and relevance of CD36 deficiency testing and the transfusion of CD36-deficient platelets.

Probability of Obtaining Specific Antigen-Negative Blood Units through Antigen Testing in Korean Medical Institutes / 대한수혈학회지

BACKGROUND: When unexpected antibodies are identified, selection for specific antigen-negative blood units is needed in order to ensure transfusion safety. We estimated the number of blood units required for antigen testing to obtain specific antigen-negative units in Korean medical institutes. METHODS: We analyzed cases of selection for specific antigen-negative units for recipients who had antibodies identified in Seoul National University Bundang hospital from January 2008 to December 2010 and cases entered into the KRBP (Korean Rare Blood Program) online database from July 2013 to February 2014 from eight medical institutes. RESULTS: A total of 559 cases of 266 patients were analyzed. The antigen types requiring two units on average for one specific antigen-negative unit were E, P1, and Lea. Three units on average were required for one Fyb-negative blood unit, four units for one Jka-negative unit, four units for one Jkb-negative unit, 4.5 units for one Leb-negative unit, five units for one C-negative unit, six units for one M-negative unit, and seven units for one S-negative unit. In cases of obtaining specific antigen-negative units for more than one antigen type, three units on average were required for one E, c-negative unit and seven units for one C, e-negative unit. Other multiple antigen-negative units required up to 20 units. CONCLUSION: The accurate antigen-negative frequency in the Korean population should be investigated. Following this effort, the number of blood units required for selection of specific antigen-negative units could be predicted and practical measures for obtaining specific antigen-negative blood units could be suggested for Korean medical institutes.

Adoption of Donor Screening Policy in a Tissue Bank at a Tertiary Hospital / 대한수혈학회지

BACKGROUND: Tissues for transplantation can save lives or restore essential functions. According to national policies and regulations, access to suitable transplantation, as well as the level of safety, quality, efficacy of donation, and transplantation of tissues, differ significantly between countries. We reviewed a few guidelines on tissue banking from the aspect of screening tests. In addition, four-year experience with screening panels for donated bones and donors at a tertiary hospital is introduced. METHODS: Seven national and international guidelines for screening tests for donors and donated tissues were reviewed. At our institution, screening tests for donation involve two steps. At retrieval, the first screening panel, including ABO/Rh typing, unexpected antibody screening, VDRL, HBsAg, anti-HBs, anti-HBc IgM, anti-HCV, anti-HIV, and microbiological cultures was performed. The second screening panel, including the same tests, except culture studies, was performed after 90 days. From 2008 to 2011, a total of 245 retrievals of bone tissue were performed and the screening panel results were analyzed. RESULTS: Mandatory screening serologic tests for living donors can differ according to local law or regulation and/or screening for endemic diseases. At our institution, among 245 donated bones for a period of four years, 61 bone tissues were discarded due to noncompliance for the second screening (n=32), contamination or no culture study results (n=9), abnormal serologic test results (n=8), and so on. CONCLUSION: Donor screening policies for tissue banking are various according to national laws or endemic disease status. Second screening tests with consideration of the window period should be adopted.

Human Platelet Antigen Genotyping Using a Multiplex Single-Base Primer Extension Reaction in Koreans / 대한수혈학회지

BACKGROUND: Alloimmunization of human platelet antigens (HPA) is associated with clinically significant disease, such as platelet refractoriness, neonatal alloimmune thrombocytopenia, or posttransfusion purpura. It is determined by single nucleotide polymorphism of genes for platelet membrane glycoprotein. To date, approximately 27 HPAs have been discovered, and their frequencies differ depending on ethnicity and country. METHODS: We conducted an investigation of prevalence of HPA in the Korean population using a multiplex single-base primer extension reaction (SNaPshot). With 84 specimens from healthy donors, HPA genotyping was performed on 11 different HPAs, including HPA-1, -2, -3, -4, -5, -6, -7, -8, -9, -13, and -15. RESULTS: A total of 90 blood samples were genotyped. The genotype frequencies of HPA were as follows: HPA-1a/1a: 100.0%, -2a/2a: 83.3%, -2a/2b: 14.3%, -2b/2b: 2.4%, -3a/3a: 39.3%, -3a/3b: 52.4%, -3b/3b: 8.3%, -4a/4a: 100.0%, -5a/5a: 95.2%, -5a/5b: 4.8%, -6a/6a: 94.0%, -6a/6b: 6.0%, -7a/7a: 100.0%, -8a/8a: 100.0%, -9a/9a: 97.6%, -9a/9b: 2.4%, -13a/13a: 100.0%, -15a/15a: 23.8%, -15a/15b: 51.2%, and -15b/15b: 25.0%. CONCLUSION: The SNaPshot assay was employed for detection of SNPs in various clinically significant HPA genes. In addition to well-known frequencies of previously reported HPA-1 to -8, this study showed frequencies of HPA-9, -13, and -15 in Koreans for the first time. The SNaPshot technique might be suitable for use in actual clinical testing in patients with platelet alloimmunization.