Reply to: Comment on: Agreement Between Fingerstick Blood Glucose and Continuous Glucose Monitor Measures Among Long‐Term Care Facility Residents

We thank Dr. Song for their thoughtful and constructive letter, “Comment on: Agreement Between Fingerstick Blood Glucose and Continuous Glucose Monitor Measures Among Long-Term Care Facility Residents” about our article [1]. We appreciate their attention to this critical issue of hypoglycemia under-detection in long-term care facilities (LTCFs) and concur with their call to revise current glucose monitoring practices to advance patient care and safety. Below, we address Dr. Song's comments and reference our prior letter for additional context on the points raised [2]. We agree with Dr. Song's sentiments about the importance of transparent reporting in observational studies, particularly disclosing the basis for inclusion and exclusion criteria, and describing any informative patterns of missing data. In reporting our findings, we adhered to the guidelines on linking data in pharmacoepidemiology and observational research [3, 4]. As delineated in our article, residents in Cohort 1 who generated continuous glucose monitoring (CGM) readings were matched to their corresponding records in the Long-Term Care Data Cooperative (LTCDC) using the date of birth, sex, LTCF name, zip code, state, and calendar day of the glucose measurements [1]. Of the 9 residents, 5 could be connected to the LTCDC electronic health records (EHRs). Among those connected, 3 residents were dropped for lacking CGM and fingerstick blood glucose (FBG) measures on the same days. To facilitate a valid comparison, it was crucial to keep only residents who had both CGM and LTCDC glucose measures. Any absence of same-day CGM-FBG measures reflects logistical and clinical factors such as variability in residents' daily care schedules, instances when FBG tests were delayed because glucose values were recently obtained or residents were asleep, periods when CGM sensors were temporarily removed, or differences in timing between routine CGM readings and FBG testing, rather than investigator exclusion of data. We recognize that the small size of Cohort 1 may have reduced the generalizability of our findings. Accordingly, we analyzed a relatively larger sample of residents in Cohort 2, for whom both CGM and FBG data were directly available, thereby circumventing the data-linkage limitations encountered in Cohort 1, where 4 out of 9 (44%) of the residents without successful linkage to the LTCDC data were necessarily excluded. The findings from both cohorts were largely consistent, lending credibility to the main conclusion: FBG fails to capture a significant proportion of hypoglycemia events compared to CGM. We emphasize that including a second, larger cohort does not eliminate issues around external validity; rather, it mitigates the issue, thereby strengthening the clinical interpretation and relevance of our findings. As we described more fully in our previous correspondence [5], we encourage future researchers to study more heterogeneous LTCF populations to enhance the generalizability of results. Sampling a diverse array of LTCFs is also important since there is facility-level variation in glucose monitoring practices, including the timing of FBG checks and hypoglycemia response protocols, which could influence the detection of hypoglycemia. Finally, we agree with Dr. Song that variation in FBG meter models can affect measurement accuracy and limit generalizability. This further underscores the advantage of CGM, which provides continuous glucose data rather than a single reading and offers a more complete and reliable picture of glycemic control. Based on our findings, reliance on EHR-based FBG data alone can lead to many undetected hypoglycemia events, and consequently, missed opportunities to de-intensify glucose-lowering therapy and prevent harmful outcomes. Although current LTCF glucose monitoring relies almost exclusively on FBG testing, our study adds to a growing body of evidence that CGM is a valuable emerging technology that could improve hypoglycemia detection in LTCFs. At the same time, it is important to acknowledge that CGM use is not without downsides. Among diabetic individuals using glucose monitoring devices, including CGMs, the most frequently reported cutaneous reaction has been allergic contact dermatitis, an inflammatory skin reaction caused by wearing the sensor for long periods and exposure to certain chemicals in the adhesive [6]. Skin tears, bruising, and bleeding might also be of concern in frail or anticoagulated LTCF residents. Although rare, local infection or cellulitis could be of concern if CGMs remain in place for longer than recommended or if hygiene is difficult to maintain. In line with Dr. Song's recommendation, CGM remains warranted for large-scale use in LTCFs, as its benefits outweigh the risks. We deeply appreciate Dr. Song's engagement with our study and the important points raised in their letter. Together, our study [1] and the accompanying letters [2, 5] form a constructive dialogue that advances the evidence base on improving glucose monitoring in LTCFs and helps set priorities for future research and clinical implementation. All authors are responsible for the content of this letter. The Long-Term Care Data Cooperative (LTCDC) is sponsored by the National Institute on Aging (NIA) through a supplemental grant (U54AG063546-S6) to the NIA Imbedded Pragmatic Alzheimer's Disease and AD-Related Dementias Clinical Trials Collaboratory (NIA IMPACT Collaboratory). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health nor the investigators of the IMPACT Collaboratory or the LTCDC. The sponsors had no role in the design, methods, subject recruitment, analysis, and preparation of the paper or any other aspect of the work. Andrew R. Zullo received grant funding from Sanofi paid directly to Brown University for collaborative research on the epidemiology of infections and vaccine use among LTCF residents. He is a U.S. Government employee; the views expressed in this manuscript are those of the author and do not necessarily reflect the position or policy of the Department of Veterans Affairs, or, the United States Government. Medha N. Munshi is a consultant for Sanofi. The other authors declare no conflicts of interest. This publication is linked to a related Letter to the Editor by Xiaohong Song To view this article, visit https://doi.org/10.1111/jgs.70204.