Objective: To establish the reference standard of the median nerve conduction study (NCS) in Korea. Methods: A total of 648 median motor and 602 median sensory NCSs from 349 Korean healthy volunteers were tested and analyzed prospectively. Equipment calibration, assessment of intraand inter-rater reliability, and the NCSs per se were conducted according to a predetermined protocol. A reference standard was established from uncertainty components for the following parameters: the onset and peak latencies; the baseline-to-peak and peak-to-peak amplitudes; the area and duration of the negative wave; and the nerve conduction velocity. The effects of sex, age and stimulation intensity were analyzed. Results: Each measured value of 648 median motor and 602 median sensory nerves were obtained and presented with both mean and expanded uncertainties, as well as mean and standard deviations. The cut-off values with expanded uncertainty were determined for different age and sex groups. After adjusting for anthropometric covariates, all parameters except duration were affected by age, and sex appeared to influence both duration and area. While stimulation intensity significantly affected some parameters including latencies, the effect sizes were negligible. Conclusion We propose the median NCS reference standard using the largest Korean dataset ever available. The use of the traceable and reliable reference standard is anticipated to promote more accurate and dependable diagnosis and appropriate management of median neuropathies in Korea.

Background: Aging leads to sarcopenia, which is characterized by reduced muscle mass and strength. Many factors, including altered muscle protein turnover, diminished neuromuscular function, hormonal changes, systemic inflammation, and the structure and composition of muscle fibers, play a crucial role in age-related muscle decline. This study explored differences in muscle fiber types contributing to overall muscle function decline in aging, focusing on individuals with hip fractures from falls. Methods: A pilot study at Chungnam National University Hospital collected muscle biopsies from hip fracture patients aged 20 to 80 undergoing surgical treatment. Muscle biopsies from the vastus lateralis and gluteus maximus were obtained during hip arthroplasty or internal fixation. Handgrip strength, calf and thigh circumference, and bone mineral density were evaluated in individuals with hip fractures from falls. We analyzed the relationships between each clinical characteristic and muscle fiber type. Results: In total, 26 participants (mean age 67.9 years, 69.2% male) were included in this study. The prevalence of sarcopenia was 53.8%, and that of femoral and lumbar osteoporosis was 19.2% and 11.5%, respectively. Vastus lateralis analysis revealed an age-related decrease in type IIx fibers, a higher proportion of type IIa fibers in women, and an association between handgrip strength and type IIx fibers in men. The gluteus maximus showed no significant correlations with clinical parameters. Conclusion This study identified complex associations between age, sex, handgrip strength, and muscle fiber composition in hip fracture patients, offering insights crucial for targeted interventions combating age-related muscle decline and improving musculoskeletal health.

Background/Aims: Gastroesophageal reflux disease (GERD) is typically managed based on the clinical phenotype. We evaluated the efficacy and safety of potassium-competitive acid blockers (PCABs) in patients with various clinical GERD phenotypes. Methods: Core databases were searched for studies comparing PCABs and proton pump inhibitors (PPIs) in clinical GERD phenotypes of erosive reflux disease (ERD), non-erosive reflux disease (NERD), PPI-resistant GERD and night-time heartburn. Additional analysis was performed based on disease severity and drug dosage, and pooled efficacy was calculated. Results: In 9 randomized controlled trials (RCTs) evaluating the initial treatment of ERD, the risk ratio for healing with PCABs versus PPIs was 1.09 (95% CI, 1.04-1.13) at 2 weeks and 1.03 (95% CI, 1.00-1.07) at 8 weeks, respectively. PCABs exhibited a significant increase in both initial and sustained healing of ERD compared to PPIs in RCTs, driven particularly in severe ERD (Los Angeles grade C/D).In 3 NERD RCTs, PCAB was superior to placebo in proportion of days without heartburn. Observational studies on PPI-resistant symptomatic GERD reported symptom frequency improvement in 86.3% of patients, while 90.7% showed improvement in PPIresistant ERD across 5 observational studies. Two RCTs for night-time heartburn had different endpoints, limiting meta-analysis. Pronounced hypergastrinemia was observed in patients treated with PCABs. Conclusions Compared to PPIs, PCABs have superior efficacy and faster therapeutic effect in the initial and maintenance therapy of ERD, particularly severe ERD. While PCABs may be an alternative treatment option in NERD and PPI-resistant GERD, findings were inconclusive in patients with night-time heartburn.

Purpose: To report a case of retrobulbar optic neuritis after COVID-19 infection.Case summary: A 20-year-old Korean man, without any previous relevant medical history, presented with sudden blurred vision in the left eye that began 6 days after a COVID-19 infection. At his initial visit, the best-corrected visual acuity in the left eye was counting fingers at 30 cm. The pupil showed a grade 2 relative afferent pupillary defect. The fundus exam was normal in both eyes. In the visual evoked potential (VEP) exam, the P100 amplitude of the left eye was decreased and delayed. Orbit magnetic resonance imaging showed asymmetric enlargement and mild enhancement in the left optic nerve. No other lesions were observed around the optic nerve. Steroid pulse therapy was started after a diagnosis of retrobulbar optic neuritis. After 1 month, the patient’s visual acuity had improved to 1.0 in the left eye. The relative afferent pupillary defect and visual field defect disappeared. On VEP, the P100 amplitude recovered, and the delay disappeared. Conclusions Retrobulbar optic neuritis is a possible neuro-ophthalmological complication of COVID-19 infection. In such cases, high-dose steroid pulse therapy may be helpful, as in the treatment of other forms of optic neuritis.

Objective: This study enrolls diverse hospitals and analyzes the differences in meal provision and nutrition management services for patients with dysphagia. Methods: A nationwide survey was conducted by mail and mobile for 850 medical institutions, and data were collected from 217 hospitals. We analyzed the status of the dysphagia diet and nutrition management by considering the type of hospital. Results: Among the hospitals surveyed, 167 (77%) provided texture-modified diets for dysphagia patients. The status of providing dysphagia diets and nutrition management for dysphagia differed depending on the institution. In particular, nutrition services for dysphagia patients in long-term care hospitals were poor. Difficulties in providing a dysphagia diet included the complexity of the cooking process, difficulty maintaining constant viscosity, difficulty in hygiene management, and low meal bills. Using commercial thickeners in cooking accounted for 72.5%, and only 41.9% of hospitals provided a commercial thickener with meals. Compared to the regular diet, the additional food cost to provide a single dysphagia diet meal was estimated to be 500-1,000 won. Based on a 5-point scale, we determined that the average scores for the importance and performance of nutrition management in patients with dysphagia were 4.29 and 3.19 points, respectively. Regardless of the type of hospital, performances of all the steps in the nutrition care process were significantly lower than their importance. Conclusion Several difficulties are encountered in meal provision and nutrition management for patients with dysphagia, including the burden of expenses and human resources. Thus, the medical fees for a dysphagia diet need to be reasonably increased. Moreover, national health insurance should additionally cover nutrition education for dysphagia patients.

Objective: Dysphagia is a common clinical condition characterized by difficulty in swallowing. It is sub-classified into oropharyngeal dysphagia, which refers to problems in the mouth and pharynx, and esophageal dysphagia, which refers to problems in the esophageal body and esophagogastric junction. Dysphagia can have a significant negative impact one’s physical health and quality of life as its severity increases. Therefore, proper assessment and management of dysphagia are critical for improving swallowing function and preventing complications. Thus a guideline was developed to provide evidence-based recommendations for assessment and management in patients with dysphagia. Methods: Nineteen key questions on dysphagia were developed. These questions dealt with various aspects of problems related to dysphagia, including assessment, management, and complications. A literature search for relevant articles was conducted using Pubmed, Embase, the Cochrane Library, and one domestic database of KoreaMed, until April 2021. The level of evidence and recommendation grade were established according to the Grading of Recommendation Assessment, Development and Evaluation methodology. Results: Early screening and assessment of videofluoroscopic swallowing were recommended for assessing the presence of dysphagia. Therapeutic methods, such as tongue and pharyngeal muscle strengthening exercises and neuromuscular electrical stimulation with swallowing therapy, were effective in improving swallowing function and quality of life in patients with dysphagia. Nutritional intervention and an oral care program were also recommended. Conclusion This guideline presents recommendations for the assessment and management of patients with oropharyngeal dysphagia, including rehabilitative strategies.

Background/Aims: To evaluate the efficacy and safety of ledipasvir/sofosbuvir (LDV/SOF) therapy in hepatitis C virus (HCV)-infected Korean patients in a real clinical setting. Methods: A total of 273 patients who received LDV/SOF therapy between May 2016 and February 2021 were consecutively enrolled and analyzed. A per-protocol analysis was performed to evaluate the virologic response. Results: Seventy-five percent were infected with genotype 1, and 25% were infected with genotype 2. A hundred eightyone (66.3%) patients had chronic hepatitis, 74 (27.1%) had compensated cirrhosis, eight (2.9%) had decompensated cirrhosis, and 10 (3.7%) had undergone liver transplantation. Undetectable HCV RNA at week 4 was achieved in 90.2% (231/256) of patients, 99.2% (250/252) achieved the end of treatment response, and 98.1% (202/206) achieved sustained virologic response at 12 weeks post-treatment (SVR12). According to liver function, the SVR12 rates were 99.3% (135/136) in chronic hepatitis, 96.4% (53/55) in compensated cirrhosis, and 100% (6/6) in decompensated cirrhosis. The SVR12 rates according to the genotype were 98.2% (167/170) for genotype 1 and 97.2% (35/36) for genotype 2. An 8-week LDV/SOF treatment in treatment-naïve chronic hepatitis patients with HCV RNA < 6,000,000 IU/mL at baseline resulted in 100% (23/23) SVR12 rates. Overall, LDV/SOF was tolerated well, with a 0.7% (2/273) discontinuation rate due to adverse events that were unrelated to LDV/SOF. Conclusions LDV/SOF is effective and safe for treating HCV-infected Korean patients with high SVR12 rates.

Background/Aims: To evaluate the effectiveness and safety of direct acting antivirals (DAAs) available in chronic kidney disease (CKD) patients with hepatitis C virus (HCV) infection in Korea. Methods: In a retrospective, multicenter cohort study, 362 patients were enrolled from 2015 to 2019. The effectiveness and safety of DAAs including glecaprevir/pibrentasvir, sofosubvir/ribavirin, ledipasvir/sofosbuvir, and daclatasvir/asunaprevir were analyzed for patients according to CKD stage. We evaluated sustained virologic response at week 12 after treatment (SVR12) as primary endpoint. The effectiveness and safety were also evaluated according to CKD stage. Results: Among 362 patients, 307 patients completed DAAs treatment and follow-up period after end of treatment. The subjects comprised 87 patients (62 with CKD stage 3 and 25 with CKD stage (4–5), of whom 22 were undergoing hemodialysis). HCV patients with CKD stage 1 and 2 (estimated glomerular filtration rate [eGFR] ≥ 60 mL/min/1.73 m2) showed SVR12 of 97.2% and 95.4% respectively. SVR12 of CKD stage 3 and 4–5 (eGFR < 60 mL/min/1.73 m2) patients was 91.9% and 91.6% respectively. Patients undergoing hemodialysis achieved SVR12 (90.9%). Treatment failure of DAAs in stage 1, 2, 3, and 4–5 was 2.8%, 2.7%, 1.6%, and 4%. DAAs showed good safety profile and did not affect deterioration of renal function. Conclusions DAAs shows comparable SVR12 and safety in CKD patients (stage 3, 4, and 5) with HCV compared with patients with stage 1 and 2. The effectiveness and safety of DAAs may be related to the treatment duration. Therefore, it is important to select adequate regimens of DAAs and to increase treatment adherence.

Objective: To develop a set of reference standards for tibial motor, common peroneal motor, sural sensory, and superficial peroneal sensory nerve conduction studies (NCSs) with expanded uncertainty in a healthy Korean population. Methods: Standardized procedures were conducted for individual lower extremity NCSs of 199 healthy participants in their 20s (n=100) and 50s (n=99). Mean values and expanded uncertainties for parameters were analyzed with thorough consideration of multiple uncertainty factors under the International Guide to the Expression of Uncertainty in Measurement. In addition, side-to-side differences in onset latency, amplitude, and nerve conduction velocity (NCV) were analyzed. Results: Mean (reference range) for distal onset latency, baseline to negative peak amplitude, NCV of tibial motor nerve in males in their 20s were 4.3 ms (3.1–5.4 ms), 7.1 mV (3.4–10.9 mV), and 50.7 m/s (42.2–59.3 m/s), respectively; sural sensory nerve baseline to negative peak amplitude in males in their 20s was 21.7 μV (8.3–35.2 μV). Including the aforementioned data, we present a vast dataset of normative mean values and expanded uncertainties for NCSs of the leg in a healthy Korean population. Furthermore, upper limits for normal side-to-side differences for onset latency, amplitude, and NCV of each nerve are suggested. Conclusion To our knowledge, this is the first study to present the reference standards of leg NCSs with consideration for multifactorial uncertainties in an Asian population. We expect these results to help practitioners make reliable and reproducible clinical decisions.

Background/Aims: For metastatic renal cell carcinoma (RCC), various prognostic scoring systems have been developed. However, owing to the low prevalence of nonclear cell RCC, the three most commonly used tools were mainly developed based on patients with clear cell histology. Accordingly, this study applied three prognostic models to Korean non-clear cell RCC patients treated with first-line temsirolimus. Methods: This study analyzed data for 74 patients with non-clear cell RCC who were treated with temsirolimus as the first-line therapy at eight medical centers between 2011 and 2016. The receiver-operating characteristic (ROC) curves for the different prognostic models were analyzed. Results: Twenty-seven (36.5%), 24 (32.4%), and 44 patients (59.5%) were assigned to the poor prognosis groups of the Memorial Sloan-Kettering Cancer Center (MSKCC), International Metastatic RCC Database Consortium (IMDC), and Advanced Renal Cell Carcinoma (ARCC) risk stratification models, respectively. All three prognostic models reliably discriminated the risk groups to predict progression-free survival and overall survival (p < 0.001). The area under the ROC curve (AUC) for progression and survival was highest for the ARCC model (0.777; 0.734), followed by the IMDC (0.756; 0.724) and the MSKCC (0.742; 0.712) models. Furthermore, the sensitivity and specificity for predicting progression were highest with the ARCC model (sensitivity 63.6%, specificity 85.7%), followed by the MSKCC (sensitivity 58.2%, specificity 86.5%) and the IMDC models (sensitivity 56.4%, specificity 85.7%). Conclusions All three prognostic models accurately predicted the survival of the non-clear cell RCC patients treated with temsirolimus as the first-line therapy. Furthermore, the ARCC risk model performed better than the other risk models in predicting survival.