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Abstract Objective To reveal the clinical features and assess risk factors linked to brain fog and its societal implications, including labor productivity, providing valuable insights for the future care of individuals who have experienced coronavirus disease 2019 (COVID‐19). Methods We analyzed a comprehensive cohort dataset comprising 1,009 patients with COVID‐19 admitted to Japanese hospitals. To assess brain fog, we analyzed patients who responded to a questionnaire indicating symptoms such as memory impairment and poor concentration. Results The prevalence of brain fog symptoms decreased 3 months posthospitalization but remained stable up to 12 months. Neurological symptoms such as taste and smell disorders and numbness at hospitalization correlated with a higher frequency of identifying brain fog as a long COVID manifestation. Our findings indicated that advanced age, female sex, a high body mass index, oxygen required during hospitalization, chronic obstructive pulmonary disease, asthma, and elevated C‐reactive protein and elevated D‐dimer levels were risk factors in patients exhibiting brain fog. Additionally, we demonstrated the negative impact of brain fog on labor productivity by presenteeism scores. Interpretations This study clarified the clinical characteristics of patients experiencing brain fog as a long COVID manifestation, specifically emphasizing neurological symptoms during hospitalization and their correlation with brain fog. Additionally, the study identified associated risk factors for its onset and revealed that the emergence of brain fog was linked to a decline in labor productivity.

Abstract Background Companion diagnostic tests play a crucial role in guiding treatment decisions for patients with non‐small cell lung cancer (NSCLC). The Oncomine Dx Target Test (ODxTT) Multi‐CDx System has emerged as a prominent companion diagnostic method. However, its efficacy in detecting driver gene mutations, particularly rare mutations, warrants investigation. Aims This study aimed to assess the performance of the ODxTT in detecting driver gene mutations in NSCLC patients. Specifically, we aimed to evaluate its sensitivity in detecting epidermal growth factor receptor (EGFR) mutations, a key determinant of treatment selection in NSCLC. Materials and Methods We conducted a retrospective analysis of NSCLC patients who underwent testing with the ODxTT at Keio University Hospital between May 2020 and March 2022. Patient samples were subjected to both DNA and RNA tests. Driver gene mutation status was assessed, and instances of missed mutations were meticulously examined. Results Of the 90 patients, five had nucleic acid quality problems, while 85 underwent both DNA and RNA tests. Driver gene mutations were detected in 56/90 (62.2%) patients. Of the 34 patient specimens, driver mutations were not detected using the ODxTT; however, epidermal growth factor receptor (EGFR) mutations were detected using polymerase chain reaction‐based testing in two patients, and a KRAS mutation was detected by careful examination of the sequence data obtained using the ODxTT in one patient. For the above three cases, carefully examining the gene sequence information obtained using the ODxTT could identify driver mutations that were not mentioned in the returned test results. Additionally, we confirmed comparable instances of overlook results for EGFR mutations in the dataset from South Korea, implying that this type of oversight could occur in other countries using the ODxTT. EGFR mutation was missed in ODxTT in Japan (6.3%, 2/32), South Korea (2.0%, 1/49), and overall (3.7%, 3/81). Conclusion Even if sufficient tumor samples are obtained, rare EGFR mutations (which are excluded from the ODxTT's genetic mutation list) might not be detected using the current ODxTT system due to the program used for sequence analysis. However, such rare EGFR mutations can still be accurately detected on ODxTT's sequence data using next‐generation sequencing.

Immunotherapy using immune checkpoint inhibitors (ICIs) has improved the prognosis of many cancers, including lung cancer. The mechanisms of development of immune-related adverse events (irAEs) after treatment with ICIs are not completely understood. Because ICIs can exacerbate opportunistic infections by altering immune conditions, potential opportunistic infections such as those caused by Epstein–Barr virus (EBV) may be involved in the development of irAEs. However, there is a lack of clinical findings that indicate the relationship between irAEs and potential opportunistic infections.Herein, we present the case of a 67-year-old man with advanced lung adenocarcinoma who developed encephalitis after the third cycle of pembrolizumab administration. Polymerase chain reaction using cerebrospinal fluid and blood samples revealed positive results for EBV. An autopsy examination revealed lymphocyte infiltration in the area surrounding the EBV-infected cells in the brain.Our case suggests that immune reconstitution occurred after the administration of ICIs, followed by an enhanced immune response to EBV that resulted in fatal encephalitis. Additional findings regarding the interaction between irAEs and opportunistic infections should be acquired to confirm this speculation.