Positivity of Rapid Antigen Testing for SARS-CoV-2 With Serial Followed-up Nasopharyngeal Swabs in Hospitalized Patients due to COVID-19

Despite the accuracy of nucleic acid amplification tests (NAATs), rapid antigen tests (RATs) for severe acute respiratory syndrome coronavirus-2 are widely used as point-of-care tests. A total of 282 pairs of reverse transcription-polymerase chain reaction and Standard Q COVID-19 Ag tests were serially conducted for 68 patients every 3–4 days until their discharge. Through a field evaluation of RATs using direct nasopharyngeal swabs, the sensitivities were 84.6% and 87.3% for E and RNA-dependent RNA polymerase (RdRp) genes, respectively, for specimens with cycle thresholds (Cts) < 25. The Ct values of E and RdRp genes for 95% detection rates by RATs were 16.9 and 18.1, respectively. The sensitivity of RAT was 48.4% after the onset of symptoms, which was not sufficient. RAT positivity gradually decreased with increased time after symptom onset and had continuously lower sensitivity than NAATs.

Effectiveness of Platelet Function Analyzer-100 for Laboratory Detection of Anti-Platelet Drug-Induced Platelet Dysfunction

BACKGROUND: High on-treatment platelet reactivity (HTPR) is the phenomenon wherein patients exhibit normal platelet activity in laboratory testing despite adequate adherence to anti-platelet treatment. We investigated the detection rates of Platelet Function Analyzer (PFA)-100 (Dade Behring AG, Düdingen, Switzerland) for drug-induced platelet dysfunction and analyzed potential contributors to HTPR with practical PFA-100 data over six years. METHODS: We used data from 6,957 patients who underwent PFA-100 testing after receiving aspirin, clopidogrel, or non-steroidal anti-inflammatory drugs (NSAIDs). Of these, 6,163 patients were tested with only the collagen/epinephrine cartridge (Col/EPI) of PFA-100; 794 were tested with both Col/EPI and the collagen/ADP cartridge (Col/ADP). We calculated PFA-100 closure time (CT) for each drug and compared the clinical and laboratory characteristics of the patients with prolonged CTs and normal CTs (i.e., HTPR). RESULTS: In Col/EPI, 73.2% (365/499), 72.6% (390/537), and 55.3% (3,442/6,228) patients showed prolonged CTs for aspirin, clopidogrel, and NSAIDs, respectively. In Col/ADP, prolonged CTs were observed in 37.4% (34/91), 43.2% (35/81), and 29.6% (200/676) of patients receiving aspirin, clopidogrel, and NSAIDs, respectively. Of the patients tested with both cartridges, 88.9% (48/54), 95.3% (41/43), and 89.0% (577/648) of the patients receiving aspirin, clopidogrel, and NSAIDs had prolonged CTs, and 10.0% (79/794) showed normal CTs regardless of drugs. For clopidogrel users (both cartridges), there were more patients with malignancies in the normal CT than prolonged CT group. CONCLUSIONS: PFA-100 is not sufficiently effective for laboratory screening of drug-induced platelet dysfunction. Malignancy may contribute to clopidogrel-related HTPR in PFA-100.

Age-related Reference Intervals for Total Collagen-I-N-terminal Propeptide in Healthy Korean Population

BACKGROUND: Procollagen type I N-terminal propeptide (PINP) is one of the most clinically useful bone formation biomarkers. Therefore, the purpose of this study was to independently evaluate the performance of automated total PINP assay and established age- and gender-specific reference intervals for PINP in healthy Korean population. METHODS: The imprecision, linearity, and detection capability of Elecsys total PINP assay was determined and reference interval was established using 599 serums from Korean population with normal bone mineral densities based on bone densitometry. Age groups were divided into 20s, 30s, 40s, 50s, 60s and over. RESULTS: Elecsys total PINP had excellent performance in imprecision, linearity, and detection capability. When partitioning age groups in Korean male and female populations, there was significant difference in total PINP between different age groups. In male populations, PINP level was decreased with increasing age, then it remained steady after middle-age. In female populations, there was a decreasing tendency similar to that in the male population with a sharp increase in the 50 to 59 age group. CONCLUSIONS: Elecsys total PINP assay showed precise and reliable performance in our study. We established age-related PINP reference intervals for Korean male and female population with normal bone mineral densities.

Necessity of Reticulocyte Calibration for More Accurate and Precise Results

No abstract available.

Proposal of Modified HIL-indices for Determining Hemolysis, Icterus and Lipemia Interference on the Beckman Coulter AU5800 Automated Platform

BACKGROUND: The amount of interference due to hemolysis, bilirubin, and lipemia can be measured on the AU5800 autoanalyzer (Beckman Coulter, USA) by spectrophotometry. This is reported as semi-quantitative indices, specifically H-index, I-index, and L-index, respectively. In this study, we evaluated the impact of interference using chemistry assays and established the concentration of interfering substances and HIL-index above which analytically significant interference exists, according to CLSI guidelines C56-A and EP7-A2. METHODS: Pooled sera including different concentrations of analytes were prepared and mixed with hemoglobin, bilirubin, or Intralipid. These samples were then tested for 35 clinical chemistry analytes by AU5800 and the bias based on interferent concentrations was computed. The interferent concentration above which significant interference exists was calculated from the 50% within-subject biological variation (desirable analytic goal), and the corresponding index was assigned. RESULTS: Among 35 items evaluated, interference was detected for 12 analytes by hemoglobin, 7 analytes by bilirubin, and 12 analytes by Intralipid. We proposed HIL-index₁ and HIL-index₂ for each analyte according to 2 different medical decision levels. HIL-index₁ and HIL-index₂ were considered more reasonable criteria than the HIL-index from the manufacturer's technical document (HIL-index(TD)). This is because HIL-index(TD) was empirically set to 5% or 10%, and had a wide tolerance range, which was not sufficient to reflect the presence of interference, compared to HIL-index₁ and HIL-index₂. CONCLUSIONS: We have demonstrated hemoglobin, bilirubin, and Intralipid interferences according to CLSI guidelines using the desirable analytic goal. Our results provide applicable information for Beckman Coulter automated chemistry analyzers.

Prevalence and Antimicrobial Susceptibility of Mycoplasma hominis, Ureaplasma urealyticum and Ureaplasma parvum in Individuals With or Without Symptoms of Genitourinary Infections

BACKGROUND: The aim of this study was to determine the prevalence and antimicrobial susceptibility of Mycoplasma hominis, Ureaplasma urealyticum, and Ureaplasma parvum among patients displaying symptoms of genitourinary infections and asymptomatic volunteers. METHODS: Genitourinary samples were collected from 897 participants (365 symptomatic patients and 532 asymptomatic volunteers). The samples were analyzed using multiplex real-time PCR (Anyplex™ II, Seegene, Korea), multiplex PCR (Seeplex®, Seegene), and Mycoplasma IST 2 Kit (bioMerieux, France). RESULTS: The prevalence of M. hominis, U. urealyticum, and U. parvum in the genitourinary samples of symptomatic patients compared with asymptomatic volunteers was 9.9% vs. 5.5%, 12.3% vs. 9.0%, and 36.4% vs. 30.8%, respectively. After eliminating cases of co-infections with other pathogens, there was a significant difference in the prevalence of M. hominis between symptomatic patients and asymptomatic volunteers (9.1% vs. 5.2%, P<0.05), but not in the prevalence of U. urealyticum and U. parvum organisms. When tested for antimicrobial susceptibility, more than 95.5% of each species were susceptible to tetracycline, doxycycline, josamycin, and pristamycin. More than 78.9% of Ureaplasma spp. were susceptible to azithromycin, erythromycin, and clarithromycin; however less than 4.2% of M. hominis were susceptible to these antibiotics. When tested with ofloxacin and ciprofloxacin, 40.9-58.9% and 9.1-25.0% of the three species were susceptible to these drugs, respectively. CONCLUSIONS: M. hominis is the leading causative pathogen for genitourinary infection; however the involvement of Ureaplasma spp. is debatable. For optimal antimicrobial therapy, the accurate detection of these organisms and determination of antimicrobial susceptibility is crucial considering their diverse antimicrobial susceptibility patterns.

Survey of Clinical Laboratory Practices for 2015 Middle East Respiratory Syndrome Coronavirus Outbreak in the Republic of Korea

BACKGROUND: It is crucial to understand the current status of clinical laboratory practices for the largest outbreak of Middle East respiratory syndrome coronavirus (MERS-CoV) infections in the Republic of Korea to be well prepared for future emerging infectious diseases. METHODS: We conducted a survey of 49 clinical laboratories in medical institutions and referral medical laboratories. A short questionnaire to survey clinical laboratory practices relating to MERS-CoV diagnostic testing was sent by email to the directors and clinical pathologists in charge of the clinical laboratories performing MERS-CoV testing. The survey focused on testing volume, reporting of results, resources, and laboratory safety. RESULTS: A total of 40 clinical laboratories responded to the survey. A total of 27,009 MERS-CoV real-time reverse transcription PCR (rRT-PCR) tests were performed. Most of the specimens were sputum (73.5%). The median turnaround time (TAT) was 5.29 hr (first and third quartile, 4.11 and 7.48 hr) in 26 medical institutions. The median TAT of more than a half of the laboratories (57.7%) was less than 6 hr. Many laboratories were able to perform tests throughout the whole week. Laboratory biosafety preparedness included class II biosafety cabinets (100%); separated pre-PCR, PCR, and post-PCR rooms (88.6%); negative pressure pretreatment rooms (48.6%); and negative pressure sputum collection rooms (20.0%). CONCLUSIONS: Clinical laboratories were able to quickly expand their diagnostic capacity in response to the 2015 MERS-CoV outbreak. Our results show that clinical laboratories play an important role in the maintenance and enhancement of laboratory response in preparation for future emerging infections.

Two Cases of Bacteremias Caused by Clostridium ramosum / 대한임상미생물학회지

Clostridium ramosum is Gram-positive anaerobic bacillus and is known as a non-pathogenic enteric bacterium. It is a member of the RIC group, which is a subgroup of Clostridium having atypical characteristics. Rarely, it has been reported as a pathogen of otitis media in young children or the cause of infection in immunosuppressed adults. Here, we report the first two Korean cases of C. ramosum bacteremia in colon cancer and pressure sore cases, respectively.

Two Cases of Enterobacter hormaechei Infection Misidentified as Cedecea davisae Infection

Enterobacteriaceae is a family of gram-negative, rod-shaped bacteria that consists of various species. Among these, members of the genus Cedecea has been reported as relatively rare causative pathogens of human infections. Commercially available automated identification systems that use biochemical reactions are known to accurately identify Enterobacteriaceae species. However, the accurate identification of some organisms with diverse biochemical profiles by these automated identification systems may be problematic. In this study, we report two cases of isolate misidentification, from patients with acute cholecystitis and deep vein thrombosis, as Cedecea davisae with VITEK II system. Both the isolates were correctly identified as Enterobacter hormaechei using gyrB gene sequence analysis. We also performed 16S rRNA sequence analyses and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analyses; however, indeterminate results were obtained from both the assays. Therefore, the sequence analysis of alternative genes, like gyrB, might be useful for accurate identification of species that belong to the family of Enterobacteriaceae.