The experience and reflections of GC labs as an independent clinical laboratory to the COVID-19 pandemic in South Korea.

BACKGROUND: Amid the COVID-19 pandemic, extensive testing was undertaken by independent clinical laboratories (ICLs), yet limited research exists on this matter. Drawing from Green Cross Laboratories (GC Labs)' pandemic response experience, this study seeks to offer insights for preparation for the next pandemic. METHODS: This retrospective study analyzed the outcomes of SARS-CoV-2 real-time reverse transcription polymerase chain reaction (SARS-CoV-2 rRT PCR) tests administered by GC Labs for COVID-19 diagnosis, upon request by different organizations, between February 2020 and April 2022. The distribution of institutions that requested the tests, the type of tests, and the positive rate were analyzed. We investigated resource allocation details. RESULTS: ICLs were responsible for conducting 85.6% of all tests carried out under South Korea's COVID-19 testing policy during the pandemic. The availability of free testing regardless of symptoms led to a significant increase in the use of pooled tests, which accounted for more than 80% of all tests conducted after August 2021. The gender and age distribution of COVID-19 cases nationwide and GC Labs' positive cases were similar. When we analyzed the positive rate by requesting organizations during the COVID-19 pandemic, despite an overall nationwide positivity rate of 35%, high-risk facilities exhibited a positivity rate of less than 5% by maintaining preemptive testing. The most notable increase in resources during the pandemic was seen in human resource input. CONCLUSIONS: South Korea's ICLs were able to conduct large volumes of testing during the COVID-19 pandemic because of their logistics and computer systems, scalable testing space, and trained testing personnel. They also had the flexibility to bring in additional resources to expand testing capacity because they are specialized testing organizations. Hence, ICLs could execute the pooled test that the government had introduced for extensive general population screening. The preemptive periodic testing of high-risk populations kept the positive rate much lower than in the general population. This study's findings will aid in refining mass testing-based policies for the next pandemic.

Different interpretations of inconclusive results of SARS-CoV-2 real-time RT PCR.

We investigated whether inconclusive results could be interpreted differently depending on the situation. First, data from retesting of the initial samples from subjects without a confirmed COVID-19 history were analyzed. And by analyzing the results of consecutive tests with new specimens after receiving inconclusive results between arrivals and locals for 2 periods. As a result, 179 of 219 cases (81.7%) showed still inconclusive or weakly positive results. If contamination is well controlled in a general laboratory, the effectiveness of retesting with the same sample is limited. The rate of the subsequently positive patient was significantly higher in locals than in arrivals and periods with a higher positive rate. The inconclusive results could be interpreted differently depending on the epidemiologic background and the positive rate at that time.

Clinical Aspects of the Dense Fine Speckled Pattern in Indirect Immunofluorescence-Antinuclear Antibody Screening and Its Association with DFS70 Autoantibodies.

GOALS: The existence of anti-dense fine speckled (DFS) 70 autoantibodies are considered an exclusionary biomarker for systemic autoimmune rheumatic diseases (SARDs). Several tests to confirm the presence of anti-DFS70 autoantibodies have been introduced, and the use of them in specimens with a DFS pattern in indirect immunofluorescence-antinuclear antibody (IIF-ANA) testing has been suggested. However, these additional tests have only been evaluated in a small number of samples; their clinical usefulness therefore requires further evaluation. METHODS: A total of 213 serum specimens showing DFS (n=155) or homogeneous (H; n=58) patterns were included. All specimens were tested by western blotting (WB) and enzyme immunoassay (EIA). Clinical information regarding SARDs was analyzed. RESULTS: The detection rates for WB and EIA for anti-DFS70 autoantibodies in specimens with a DFS pattern were 86.5% and 73.5%, respectively. Detection rates in specimens with a low IIF-ANA titer were significantly lower than those in specimens with a high titer. The detection rate of anti-DFS70 autoantibodies in 58 specimens with an H pattern was 10.3% (6/58). Among 155 subjects with a DFS pattern in IIF-ANA staining, only five were diagnosed with SARD. CONCLUSIONS: There is little need to confirm the presence of anti-DFS70 autoantibodies using other methods. When a DFS pattern is observed in IIF-ANA staining, it is more important to confirm the presence of other autoantibodies related to SARDs than to identify anti-DFS70 autoantibodies. Finally, more careful interpretation of IIF-ANA to specimens with a low IIF-ANA titer is needed.

Clinical use of anti-DFS70 autoantibodies.

The dense fine speckled (DFS) nuclear pattern is one of the most common indirect immunofluorescence (IIF) patterns detected during routine anti-nuclear antibody (ANA) screening. There is a negative association between anti-DFS70 status and systemic autoimmune rheumatic disease (SARD), especially in the absence of concomitant SARD-specific autoantibodies. The purpose of this study was to determine the need for confirming anti-DFS70 status when a DFS pattern is observed in IIF-ANA. The frequency of anti-DFS70 detection on Western blot and the positive rate of connective tissue disease (CTD)-related autoantibody screening with a fluorescence-based enzyme immunoassay was evaluated in DFS (n = 182) and non-DFS (n = 359) groups. Specific autoantibodies against 15 autoantigens were identified by line immunoassay. We evaluated the frequency of cases of DFS mistaken for non-DFS and non-DFS cases mistaken for DFS, as well as the clinical impacts of these misinterpretations. Among cases of IIF-ANA with an observable DFS pattern, 68.1% had only anti-DFS70 without CTD-related autoantibodies, 20.3% were false positive for IIF-ANA, and the remaining 11.5% had CTD-related autoantibodies independent of anti-DFS70 status. These results indicated that CTD-related autoantibodies may be present with or without anti-DFS70 even if a DFS pattern is observed in IIF-ANA. Among patients who are ANA negative or have a low probability of SARD, an anti-DFS70 confirmation test has no clinical benefit and cannot replace specific tests for detecting CTD-related autoantibodies. Specific tests to detect CTD-related autoantibodies should be performed instead of anti-DFS70 confirmation tests when a DFS pattern is observed in IIF-ANA.

Masked monoclonal gammopathy in capillary electrophoresis.

BACKGROUND: Although the method of choice to detect M-protein is electrophoresis on an agarose gel, such gel electrophoresis (GE) is labor-intensive, time-consuming, and not standardized. In contrast to GE, capillary electrophoresis (CE) has some merits because it is automated, fast, and highly reproducible. However, CE results occasionally make the interpretation difficult and require additional confirmatory tests like GE. METHODS: In order to assist a correct reporting of CE results and compatible interpretations between two different electrophoresis methods, we report here two unusual cases of monoclonal gammopathy by a pattern of polyclonal gammopathy upon CE interpretation in patients with end stage renal disease and multiple myeloma. RESULTS: In these cases, serum CE showed the broad bumpy peak in the gamma region. This bumpy peak does not drop completely flat after the reaction with anti-FLC. CONCLUSIONS: Because the plasma cell is a B-cell lineage and plays an important role in adaptive immunity, MG accompanying with PG is not rarely found in plasma cell dyscrasia. If the broad bumpy peak is observed in CE, careful examinations must be done to rule out the hidden M-peak. In our cases, a parallel use of gel-based methods was very helpful as it revealed monoclonal bands.

Comparison of two molecular methods for detecting toxigenic Clostridium difficile.

BACKGROUND: Clostridium difficile is one of the most common causes of nosocomial diarrhea, and diagnostic methods for detecting C. difficile infection have shifted from conventional to more recent molecular techniques. This study aimed to compare the performance of two molecular assays (Meridian Illumigene™ and AdvanSure CD real-time PCR) in detecting C. difficile using a toxigenic culture as a reference standard. MATERIALS AND METHODS: This study was conducted at Kyung Hee University Hospital, a tertiary university teaching hospital in Seoul, Korea, from July 2010 to February 2011. The study used 203 fresh diarrheal stools. All fecal specimens were immediately tested by culture and the VIDAS C. difficile toxin A & B assay using an automated VIDAS immunoanalyzer. The remainder was stored at -70°C until required for AdvanSure CD real-time polymerase chain reaction and Illumigene™. The alcohol shock procedure was then performed. Aliquots were inoculated directly on C. difficile-selective agar and blood agar and then incubated in an anaerobic jar for 48 h at 35°C. The Rapid ID 32 A test was used for specifying colonies on plates. The AdvanSure CD real-time PCR was used to detect the tcdA and tcdB gene, and PCR Illumigene™ kits were used to detect the tcdA gene of the pathogenicity locus (PaLoc) harboring toxigenic C. difficile. RESULTS: Of 203 clinical samples, 197 showed identical results between the two molecular assays, with a concordance rate of 97.0%. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were as follows: Illumigene: 92.3, 99.4, 96.0, and 98.9, respectively; AdvanSure CD real-time PCR: 84.6, 98.3, 88.0, and 97.8, respectively. CONCLUSIONS: Both molecular assays demonstrated good sensitivity and specificity. Additionally, both molecular assays showed comparable results to those of a toxigenic culture, albeit with a slight decrease in test sensitivity and specificity.

Combined Bacillus licheniformis and Bacillus subtilis infection in a patient with oesophageal perforation.

Species of the genus Bacillus are a common laboratory contaminant, therefore, isolation of these organisms from blood cultures does not always indicate infection. In fact, except for Bacillus anthracis and Bacillus cereus, most species of the genus Bacillus are not considered human pathogens, especially in immunocompetent individuals. Here, we report an unusual presentation of bacteraemia and mediastinitis due to co-infection with Bacillus subtilis and Bacillus licheniformis, which were identified by 16S RNA gene sequencing, in a patient with an oesophageal perforation.