Background: Commutability refers to the consistency of results from different measurement procedures in regards to a reference material (RM) and representative samples. In this study, we evaluated the commutability of laboratory-prepared pooled sera and commercial quality control materials in the thyroid-stimulating hormone (TSH) proficiency testing program of the Korean Association of External Quality Assessment Service. Methods: Serum TSH from 30 patients was measured in triplicate. Two levels of lab-prepared pooled sera and three levels of commercial materials (Bio-Rad Liquichek Immunoassay Plus) were tested in triplicate at five positions per immunoassay platform (Beckman Coulter UniCel DxI 800, Abbott Alinity i, Roche Cobas e801, Siemens Atellica IM 1600). Commutability was assessed by comparing method differences in patient samples to RMs using the ‘International Federation of Clinical Chemistry and Laboratory Medicine’ protocol with a desirable bias of 10% based on biological variation. Results: The median TSH level for the 30 patient samples was 2.51–3.07 μIU/mL, with a coefficient of variation ranging from 1.51% to 4.32%.The median TSH levels of the in-house prepared materials were 0.912– 1.01 μIU/mL for RM2 and 9.10–10.9 μIU/mL for RM4. The median TSH levels of the commercial materials were 0.391–0.464 μIU/mL for RM1, 4.39–5.24 μIU/mL for RM3, and 28.2–35.5 μIU/mL for RM5. The in-house prepared materials (RM2, RM4) demonstrated commutability across all six method combinations. Among the commercial materials, RM1 and RM3 showed commutability in four method combinations, while RM5 showed commutability in three method combinations. Conclusions The evaluation results for the TSH proficiency testing materials showed that the in-house prepared materials had higher commutability than the commercial materials.

Background: Commutability refers to the consistency of results from different measurement procedures in regards to a reference material (RM) and representative samples. In this study, we evaluated the commutability of laboratory-prepared pooled sera and commercial quality control materials in the thyroid-stimulating hormone (TSH) proficiency testing program of the Korean Association of External Quality Assessment Service. Methods: Serum TSH from 30 patients was measured in triplicate. Two levels of lab-prepared pooled sera and three levels of commercial materials (Bio-Rad Liquichek Immunoassay Plus) were tested in triplicate at five positions per immunoassay platform (Beckman Coulter UniCel DxI 800, Abbott Alinity i, Roche Cobas e801, Siemens Atellica IM 1600). Commutability was assessed by comparing method differences in patient samples to RMs using the ‘International Federation of Clinical Chemistry and Laboratory Medicine’ protocol with a desirable bias of 10% based on biological variation. Results: The median TSH level for the 30 patient samples was 2.51–3.07 μIU/mL, with a coefficient of variation ranging from 1.51% to 4.32%.The median TSH levels of the in-house prepared materials were 0.912– 1.01 μIU/mL for RM2 and 9.10–10.9 μIU/mL for RM4. The median TSH levels of the commercial materials were 0.391–0.464 μIU/mL for RM1, 4.39–5.24 μIU/mL for RM3, and 28.2–35.5 μIU/mL for RM5. The in-house prepared materials (RM2, RM4) demonstrated commutability across all six method combinations. Among the commercial materials, RM1 and RM3 showed commutability in four method combinations, while RM5 showed commutability in three method combinations. Conclusions The evaluation results for the TSH proficiency testing materials showed that the in-house prepared materials had higher commutability than the commercial materials.

Background: Commutability refers to the consistency of results from different measurement procedures in regards to a reference material (RM) and representative samples. In this study, we evaluated the commutability of laboratory-prepared pooled sera and commercial quality control materials in the thyroid-stimulating hormone (TSH) proficiency testing program of the Korean Association of External Quality Assessment Service. Methods: Serum TSH from 30 patients was measured in triplicate. Two levels of lab-prepared pooled sera and three levels of commercial materials (Bio-Rad Liquichek Immunoassay Plus) were tested in triplicate at five positions per immunoassay platform (Beckman Coulter UniCel DxI 800, Abbott Alinity i, Roche Cobas e801, Siemens Atellica IM 1600). Commutability was assessed by comparing method differences in patient samples to RMs using the ‘International Federation of Clinical Chemistry and Laboratory Medicine’ protocol with a desirable bias of 10% based on biological variation. Results: The median TSH level for the 30 patient samples was 2.51–3.07 μIU/mL, with a coefficient of variation ranging from 1.51% to 4.32%.The median TSH levels of the in-house prepared materials were 0.912– 1.01 μIU/mL for RM2 and 9.10–10.9 μIU/mL for RM4. The median TSH levels of the commercial materials were 0.391–0.464 μIU/mL for RM1, 4.39–5.24 μIU/mL for RM3, and 28.2–35.5 μIU/mL for RM5. The in-house prepared materials (RM2, RM4) demonstrated commutability across all six method combinations. Among the commercial materials, RM1 and RM3 showed commutability in four method combinations, while RM5 showed commutability in three method combinations. Conclusions The evaluation results for the TSH proficiency testing materials showed that the in-house prepared materials had higher commutability than the commercial materials.

Background: This study aimed to investigate the erosive potential of powdered vitamin C on the bovine enamel tooth surface. Methods: The experiment included five groups: Lemona, Vitagran, Korea Eundan, Coca-Cola (positive controls), and artificialsaliva (negative controls). The pH and titratable acidity were measured. Bovine enamel specimens were immersed in the experimental solutions for 15 minutes each day for 7 days. The surface microhardness was measured using the Vickers hardness number before immersion and on the 1st, 3rd, 5th, and 7th days. The surfaces of the bovine enamel specimens were observed by scanning electron microscopy (SEM). Results: The pH of the experimental groups was as follows: Lemona (2.04±0.04) had the lowest pH, followed by Vitagran(2.56±0.01), the positive control group Coca-Cola (2.60±0.03), Korea Eundan (3.14±0.02), and the negative control group artificial saliva (7.06±0.05). Surface microhardness decreased significantly during the immersion period (p＜0.001). The largest surface microhardness reduction value was shown in Lemona (–201.22±20.60), followed by Vitagran (–190.02±14.73), Korea Eundan (–189.27±27.14), Coca-Cola (–99.28±17.21), artificial saliva (–10.99±9.94). According to the SEM findings, the experimental and positive control groups exhibited rough surfaces with micropores, whereas the negative control group exhibited smooth surfaces before specimen immersion. Conclusion Consuming powdered vitamin C at a low pH may degrade the enamel surface. To reduce the erosive effect, it isrecommended to rinse the mouth with water and brush the teeth after an hour.

Background: This study aimed to investigate the erosive potential of powdered vitamin C on the bovine enamel tooth surface. Methods: The experiment included five groups: Lemona, Vitagran, Korea Eundan, Coca-Cola (positive controls), and artificialsaliva (negative controls). The pH and titratable acidity were measured. Bovine enamel specimens were immersed in the experimental solutions for 15 minutes each day for 7 days. The surface microhardness was measured using the Vickers hardness number before immersion and on the 1st, 3rd, 5th, and 7th days. The surfaces of the bovine enamel specimens were observed by scanning electron microscopy (SEM). Results: The pH of the experimental groups was as follows: Lemona (2.04±0.04) had the lowest pH, followed by Vitagran(2.56±0.01), the positive control group Coca-Cola (2.60±0.03), Korea Eundan (3.14±0.02), and the negative control group artificial saliva (7.06±0.05). Surface microhardness decreased significantly during the immersion period (p＜0.001). The largest surface microhardness reduction value was shown in Lemona (–201.22±20.60), followed by Vitagran (–190.02±14.73), Korea Eundan (–189.27±27.14), Coca-Cola (–99.28±17.21), artificial saliva (–10.99±9.94). According to the SEM findings, the experimental and positive control groups exhibited rough surfaces with micropores, whereas the negative control group exhibited smooth surfaces before specimen immersion. Conclusion Consuming powdered vitamin C at a low pH may degrade the enamel surface. To reduce the erosive effect, it isrecommended to rinse the mouth with water and brush the teeth after an hour.

Background: Commutability refers to the consistency of results from different measurement procedures in regards to a reference material (RM) and representative samples. In this study, we evaluated the commutability of laboratory-prepared pooled sera and commercial quality control materials in the thyroid-stimulating hormone (TSH) proficiency testing program of the Korean Association of External Quality Assessment Service. Methods: Serum TSH from 30 patients was measured in triplicate. Two levels of lab-prepared pooled sera and three levels of commercial materials (Bio-Rad Liquichek Immunoassay Plus) were tested in triplicate at five positions per immunoassay platform (Beckman Coulter UniCel DxI 800, Abbott Alinity i, Roche Cobas e801, Siemens Atellica IM 1600). Commutability was assessed by comparing method differences in patient samples to RMs using the ‘International Federation of Clinical Chemistry and Laboratory Medicine’ protocol with a desirable bias of 10% based on biological variation. Results: The median TSH level for the 30 patient samples was 2.51–3.07 μIU/mL, with a coefficient of variation ranging from 1.51% to 4.32%.The median TSH levels of the in-house prepared materials were 0.912– 1.01 μIU/mL for RM2 and 9.10–10.9 μIU/mL for RM4. The median TSH levels of the commercial materials were 0.391–0.464 μIU/mL for RM1, 4.39–5.24 μIU/mL for RM3, and 28.2–35.5 μIU/mL for RM5. The in-house prepared materials (RM2, RM4) demonstrated commutability across all six method combinations. Among the commercial materials, RM1 and RM3 showed commutability in four method combinations, while RM5 showed commutability in three method combinations. Conclusions The evaluation results for the TSH proficiency testing materials showed that the in-house prepared materials had higher commutability than the commercial materials.

Background: This study aimed to investigate the erosive potential of powdered vitamin C on the bovine enamel tooth surface. Methods: The experiment included five groups: Lemona, Vitagran, Korea Eundan, Coca-Cola (positive controls), and artificialsaliva (negative controls). The pH and titratable acidity were measured. Bovine enamel specimens were immersed in the experimental solutions for 15 minutes each day for 7 days. The surface microhardness was measured using the Vickers hardness number before immersion and on the 1st, 3rd, 5th, and 7th days. The surfaces of the bovine enamel specimens were observed by scanning electron microscopy (SEM). Results: The pH of the experimental groups was as follows: Lemona (2.04±0.04) had the lowest pH, followed by Vitagran(2.56±0.01), the positive control group Coca-Cola (2.60±0.03), Korea Eundan (3.14±0.02), and the negative control group artificial saliva (7.06±0.05). Surface microhardness decreased significantly during the immersion period (p＜0.001). The largest surface microhardness reduction value was shown in Lemona (–201.22±20.60), followed by Vitagran (–190.02±14.73), Korea Eundan (–189.27±27.14), Coca-Cola (–99.28±17.21), artificial saliva (–10.99±9.94). According to the SEM findings, the experimental and positive control groups exhibited rough surfaces with micropores, whereas the negative control group exhibited smooth surfaces before specimen immersion. Conclusion Consuming powdered vitamin C at a low pH may degrade the enamel surface. To reduce the erosive effect, it isrecommended to rinse the mouth with water and brush the teeth after an hour.

Background: Commutability refers to the consistency of results from different measurement procedures in regards to a reference material (RM) and representative samples. In this study, we evaluated the commutability of laboratory-prepared pooled sera and commercial quality control materials in the thyroid-stimulating hormone (TSH) proficiency testing program of the Korean Association of External Quality Assessment Service. Methods: Serum TSH from 30 patients was measured in triplicate. Two levels of lab-prepared pooled sera and three levels of commercial materials (Bio-Rad Liquichek Immunoassay Plus) were tested in triplicate at five positions per immunoassay platform (Beckman Coulter UniCel DxI 800, Abbott Alinity i, Roche Cobas e801, Siemens Atellica IM 1600). Commutability was assessed by comparing method differences in patient samples to RMs using the ‘International Federation of Clinical Chemistry and Laboratory Medicine’ protocol with a desirable bias of 10% based on biological variation. Results: The median TSH level for the 30 patient samples was 2.51–3.07 μIU/mL, with a coefficient of variation ranging from 1.51% to 4.32%.The median TSH levels of the in-house prepared materials were 0.912– 1.01 μIU/mL for RM2 and 9.10–10.9 μIU/mL for RM4. The median TSH levels of the commercial materials were 0.391–0.464 μIU/mL for RM1, 4.39–5.24 μIU/mL for RM3, and 28.2–35.5 μIU/mL for RM5. The in-house prepared materials (RM2, RM4) demonstrated commutability across all six method combinations. Among the commercial materials, RM1 and RM3 showed commutability in four method combinations, while RM5 showed commutability in three method combinations. Conclusions The evaluation results for the TSH proficiency testing materials showed that the in-house prepared materials had higher commutability than the commercial materials.

Background: Limited data are available on the mortality rates of patients receiving extracorporeal membrane oxygenation (ECMO) support for coronavirus disease 2019 (COVID-19). We aimed to analyze the relationship between COVID-19 and clinical outcomes for patients receiving ECMO. Methods: We retrospectively investigated patients with COVID-19 pneumonia requiring ECMO in 19 hospitals across Korea from January 1, 2020 to August 31, 2021. The primary outcome was the 90-day mortality after ECMO initiation. We performed multivariate analysis using a logistic regression model to estimate the odds ratio (OR) of 90-day mortality. Survival differences were analyzed using the Kaplan–Meier (KM) method. Results: Of 127 patients with COVID-19 pneumonia who received ECMO, 70 patients (55.1%) died within 90 days of ECMO initiation. The median age was 64 years, and 63% of patients were male. The incidence of ECMO was increased with age but was decreased after 70 years of age. However, the survival rate was decreased linearly with age. In multivariate analysis, age (OR, 1.048; 95% confidence interval [CI], 1.010–1.089; P = 0.014) and receipt of continuous renal replacement therapy (CRRT) (OR, 3.069; 95% CI, 1.312–7.180; P = 0.010) were significantly associated with an increased risk of 90-day mortality. KM curves showed significant differences in survival between groups according to age (65 years) (log-rank P = 0.021) and receipt of CRRT (log-rank P = 0.004). Conclusion Older age and receipt of CRRT were associated with higher mortality rates among patients with COVID-19 who received ECMO.

Dysphagia frequently presents in patients with a cervical spinal cord injury following anterior cervical spine fusion (ACSF). However, it is essential to identify the cause of dysphagia because it can occur due to a variety of reasons, such as structural lesions, psychiatric problems, as well as neurologic impairment. We report two cases of dysphagia as secondary postoperative complications after ACSF. The first case was a 60-year-old male who experienced pain while swallowing, having undergone C3/4 ACSF due to traumatic retrolisthesis at C3/4. A videofluoroscopic swallowing study (VFSS) demonstrated a delayed swallowing reflex and liquid penetration. A cervical spine magnetic resonance imaging (MRI) showed a deep neck infection at the C4-7 level. Following intravenous antibiotic administration, the patient’s pain significantly improved. The second case was that of a 74-year-old female who underwent C3/4 ACSF due to an accidental fall. A VFSS demonstrated post-swallowing liquid aspiration. However, she complained of a foreign sensation in the throat and aspiration. A cervical spine computed tomography (CT) showed a suspected hardware loosening, which interfered with the passage of food. In patients with a cervical spinal cord injury, mechanical problems related to the surgery can be a cause of swallowing difficulty. Prompt identification and treatment of these complications are essential for patient recovery.