IgG Seroprevalence of COVID-19 among Individuals without a History of the Coronavirus Disease Infection in Daegu, Korea.

BACKGROUND: Seroprevalence studies of coronavirus disease 2019 (COVID-19) from many countries have shown that the number of undiagnosed missing cases is much larger than that of confirmed cases, irrespective of seroprevalence levels. Considering the strategy of Korea entailing massive testing and contact tracing from the beginning of epidemic, the number of undiagnosed missing cases in Korea may be negligible. This study was conducted to estimate the seroprevalence of COVID-19 among individuals who were never diagnosed with COVID-19 in Daegu, the epicenter of COVID-19 epidemic in Korea. METHODS: Serologic testing for immunoglobulin G antibody based on immunochromatographic assay was conducted in 103 patients and 95 guardians aged 18 to 82 years without any history of COVID-19 diagnosis, who visited outpatient clinics of a single university-affiliated hospital from May 25 to June 5, 2020. RESULTS: The estimated seroprevalence was 7.6% (95% confidence interval, 4.3%-12.2%) with 15 positive cases. Among them, only one had a polymerase chain reaction (PCR)-confirmed case among their close contacts and 13 did not experience COVID-19-related symptoms. Seroprevalence was similar between patients and guardians. Based on this figure, the number of undiagnosed missing cases in Daegu was estimated to be a dozen times more than the number of confirmed cases based on PCR testing. CONCLUSION: Despite the limitation of a small and unrepresentative sample, this is the first study on seroprevalence of COVID-19 in Korea. Our study suggested that the number of undiagnosed missing cases was substantial even with the stringent strategy adopted in Korea, similar to that of other countries.

The Effect of Positive Medial Cortical Support in Reduction of Pertrochanteric Fractures with Posteromedial Wall Defect Using a Dynamic Hip Screw.

BACKGROUND: We evaluated the radiological and clinical results of reduction using a dynamic hip screw according to the grade of medial cortical support in patients with AO Foundation and Orthopaedic Trauma Association (AO/OTA) classification type 31-A2 pertrochanteric fractures. METHODS: We enrolled 100 patients with AO/OTA type 31-A2 fractures with displaced lesser trochanter fragments (length of the cortical area longer than 20 mm on the pelvis anteroposterior view). Patients with positive medial cortical support were assigned to group 1 (n = 28); neutral medial cortical support, group 2 (n = 42); and negative medial cortical support, group 3 (n = 30). Radiological evaluation was done by measuring the change in the femoral neck-shaft angle and sliding distance of the lag screw. Clinical outcomes of each group were compared by means of the walking ability score proposed by Ceder. RESULTS: Group 1 showed significantly less changes in the femoral neck-shaft angle and shorter sliding distance than groups 2 and 3. Group 2 showed significantly less changes in the femoral neck-shaft angle and shorter sliding distance than group 3. Group 1 showed significantly higher walking ability scores than group 3 (p = 0.00). The use of trochanter stabilizing plates or fixation using wires for posteromedial wall defect resulted in no significant changes in terms of the femoral neck-shaft angle or sliding distance. CONCLUSIONS: In the treatment of pertrochanteric fractures accompanied by posteromedial wall defect using a dynamic hip screw, reduction with negative cortical support should be avoided.