· In 69 hospitalized children and adolescents with type 1 diabetes, factory-calibrated Dexcom G6 and G7 sensors reached a mean absolute relative difference below 10% by day 6 and day 4, respectively. Accuracy improved with each wear day and was maintained across ward and intensive care settings. After a brief stabilization period, both systems met ISO (International Organization for Standardization) 15197:2013 and U.S. Food and Drug Administration integrated-continuous glucose monitoring accuracy criteria.

Type 1 diabetes mellitus (T1DM) is relatively uncommon in children in Asia. Nationwide registry data from Korea indicate that the annual incidence of T1DM among individuals younger than 30 years rose from 3.02 to 3.75 per 100,000 between 2008 and 2021, while the prevalence more than doubled, from 21.82 to 46.41 per 100 000 over the same period [1]. Global modeling suggests that 8.4 million people were living with T1DM in 2021 and that this figure could reach 13.5–17.4 million by 2040, with the steepest relative increases expected in low-income and lower-middle-income countries [2]. These epidemiological trends, together with rapid improvements in sensor chemistry, algorithm design, wireless data transmission, and expanded national insurance reimbursements, have dramatically increased the use of real-time continuous glucose monitoring (CGM) among children and adolescents in Korea and worldwide [3,4].

T1D requires rigorous glycemic control to prevent acute crises, such as diabetic ketoacidosis (DKA), and mitigate long-term microvascular and macrovascular complications [5-7]. Capillary self-monitoring of blood glucose (SMBG) has long been the standard of care; however, capillary fingerstick testing provides intermittent point-in-time measurements and often misses rapid excursions, notably nocturnal hypoglycemia [8]. CGM closes this gap by delivering real-time interstitial glucose values, trend arrows, and customizable alerts. Randomized outpatient trials in pediatric T1DM cohorts demonstrated that CGM lowers glycated hemoglobin (HbA1c) levels and reduces exposure to both severe hypo- and hyperglycemia [9].

Over the past decade, sensor accuracy has markedly improved. Factory-calibrated systems such as Dexcom G6 and the next-generation G7 now report overall mean absolute relative differences (MARDs) below 9%, satisfying U.S. Food and Drug Administration (FDA) integrated-CGM (iCGM) criteria that require more than 87% of readings within ±20% or ±20 mg/dL of reference plasma glucose [10]. A recent durability study of a 15-day factory -calibrated sensor involving both adult and pediatric participants (age range, 2–17 years) confirmed an aggregate MARD of approximately 8%, with 94% of values within the 20/20 accuracy envelope [11]. A head-to-head trial showed that G7 achieved a lower MARD (8.9%) than G6 (13.6%), and a greater share of readings within ±20 mg/dL of the reference (91.4% vs 78.6%) [12]. These data highlight the point-wise accuracy that is now attainable, which is essential for CGM-guided insulin dosing and automated insulin delivery systems. However, most evidence has been derived from ambulatory adults, and pediatric inpatients present unique physiological and operational challenges that can reduce accuracy.

The coronavirus disease 2019 (COVID-19) pandemic accelerated the adoption of inpatient CGM through regulatory waivers designed to minimize direct patient contact [13,14]. Early implementation studies confirmed feasibility but reported highly variable accuracy: aggregate inpatient MARDs from 9% to 20%, particularly in intensive care units (ICUs) [10]. However, most available data are derived from adult populations, often with steroid-induced hyperglycemia, leaving pediatric-specific evidence limited and highlighting the need to investigate factors influencing CGM performance in hospitalized children.

The accuracy of CGM in pediatric inpatients is influenced by several factors. Wear-day effects remain prominent; Dexcom G6 MARD falls from 13.4% on day 1 to 9.1% on day 3 in hospitalized adolescents [15]. Moreover, clinical setting also matters, with adult data showing the MARD climbing from 12.0% in general wards to 16.1% in critical-care units. Similar stressors in pediatric ICUs (hypoperfusion, vasoactive infusions, edema, and frequent arterial samples) likely have comparable effects [16]. Accuracy further varies with the glucose range; the relative error is modest in euglycemia, spikes in hypoglycemia, and the absolute error widens during marked hyperglycemia [17]. Therefore, any pediatric inpatient accuracy study should stratify the results by sensor day, care setting, and glucose range to capture distinct sources of variability.

Therefore, we conducted a retrospective study at a tertiary children's hospital to evaluate the clinical accuracy of Dexcom G6 and G7 in hospitalized pediatric patients with T1DM. Accuracy metrics (MARD, MAD, Clarke error grid, Bland-Altman analysis) were assessed by glucose range, sensor day, care setting, and device type to identify patterns over time and factors affecting performance. These findings aim to inform safe and effective CGM use in hospitalized pediatric patients with T1DM.

In this retrospective, single-center study of hospitalized pediatric patients with T1DM, factory-calibrated Dexcom G6 and G7 CGM systems demonstrated clinically acceptable accuracy following a brief postinsertion stabilization period. On day 1, the MARD was 13% for G6 and 11% for G7, yet values decreased below the 10% clinical-accuracy threshold by day 4 with G7 and by days 6 with G6, thereafter stabilizing at 6%–8%, with a corresponding MAD of approximately 10–12 mg/dL. These improvements were accompanied by a progressive narrowing of the 95% Bland-Altman LoA, which contracted from ±60 mg/dL on day 1 to ±35–39 mg/dL after day 3. Concomitantly, Clarke error grid zone A readings increased to more than 85% (zones A + B ≈ 97%), confirming performance that met both ISO 15197:2013 and U.S. FDA accuracy benchmarks for therapeutic inpatient CGM use [10,22,23,27].

The time-dependent accuracy gains observed in our cohort mirror those reported in adult outpatient studies, which have demonstrated MARD reductions of 20%–40% within the first 48–72 hours after sensor insertion [28]. While the biological underpinnings of this early variability are not fully understood, transient biofouling and a local foreign-body response are plausible contributors [29]. The G7’s rapid stabilization—achieving MARD <10% by day 4 versus day 6 for G6—is likely attributable to improvements including a shorter introducer needle, updated enzyme formulation, and an enhanced algorithm [11,12], resulting in a clinically meaningful 2-day reduction in sensor "time-to-trust" when sensors are placed on admission.

Although G7 consistently achieved lower absolute MARD levels and crossed <10% earlier (day 4), its adjusted linear wear-day slope for MARD did not reach statistical significance. This likely reflects a floor effect and a nonlinear trajectory characterized by early improvement during days 1–4 followed by rapid stabilization, as visually corroborated by the LOESS-smoothed curves in Fig. 1. In contrast, G6 started from a higher day-1 MARD and showed a larger per-day reduction, yielding a significant linear slope in mixed-effects models.

Accuracy varied by glycemic range: MAD was highest during hyperglycemia (≈21 mg/dL) and lowest during hypoglycemia (≈9 mg/dL). In contrast, MARD was lowest during hyperglycemia (8.5%) and peaked during hypoglycemia (15.2%). This pattern, consistent with prior pediatric inpatient CGM studies, reflects the intrinsic proportional relationship between sensor error and glucose level [17,30]. Despite higher proportional error during hypoglycemia, the associated absolute deviation remained modest (±9 mg/dL at 60 mg/dL), supporting overall safety while still justifying clinical confirmation of low-glucose alarms [19].

Critically ill patients admitted to the ICU exhibited higher MAD (+5.69 mg/dL) but no significant increase in MARD compared to those on the general ward. These results differ from adult data, where vasopressor use and tissue hypoperfusion often impair CGM accuracy [14]. Similar pediatric studies on DKA admissions have reported MARD values of 7%–11% once acidosis resolves [28-31], suggesting that better peripheral perfusion, shorter ICU stays, and careful sensor-site selection mitigate many ICU-specific challenges. Nevertheless, clinicians should be cautious during episodes of hemodynamic instability or severe acidosis when transient inaccuracies may still arise [30].

In the ICU subset, the counterintuitive gradient of error (mild>moderate>severe DKA) likely reflects a convergence of clinical and methodological factors. Mild DKA patients were more often instrumented immediately on admission, yielding a larger share of day-1 to day-2 measurements when early postinsertion stabilization inflates error, whereas severe DKA patients tended to have sensors placed after initial resuscitation or contributed more wear days beyond day 3, when accuracy improves. Faster glycemic rate of change during ambulation and intermittent corrections in milder illness magnifies interstitial-plasma lag and increases proportional error, and greater activity also predisposes to micromotion and compression artifacts that elevate absolute error. By contrast, severe cases typically had stricter site selection and fixation and less movement, creating a more stable sensing environment.

Throughout the observation period, the G7 consistently posted MARD values 1%–2% lower than those of the G6 and crossed the 10% threshold 2 days sooner. Although the study was not powered for formal noninferiority testing, the effect size aligned with outpatient adult trials that showed a 30%–40% MARD reduction with the G7 [12]. Importantly, both devices ultimately satisfied the ISO targets after their respective break-in phases, indicating that either system can be safely deployed in hospitalized youths.

An overall MARD of approximately 10% is comparable to the intrinsic error of many hospital POC glucometers currently used to guide insulin dosing [20,27]. With more than 94% of CGM values falling in Clarke error grid zones A and B at every time point, most readings would lead to identical or clinically benign decisions relative to fingerstick results. Continuous surveillance also addresses the major limitations of intermittent bedside testing by reducing the risk of missing nocturnal hypoglycemia or rapid glycemic excursions. In addition, it decreases the nursing workload and minimizes patient discomfort [13,14,30].

The recent Korean experience during the COVID-19 pandemic further demonstrates CGM’s utility once children have transitioned out of the hospital. A multicenter telehealth program found that approximately 70% of Korean youths with T1DM were already using CGM and could be managed safely at home during mandatory quarantine without episodes of severe glycemic decompensation [32]. In a separate cohort, CGM metrics captured a brief rise in glucose management indicators and time-above-range during mild severe acute respiratory syndrome coronavirus 2 infection that normalized within 2 weeks. Children on insulin pumps showed significantly smaller excursions than those on multiple daily injections, underscoring the synergistic benefit of advanced insulin delivery and real-time sensing [33]. These real-world data highlight CGM's capacity to support continuous, remote decision-making under acute stress and reinforce its role as a cornerstone of comprehensive pediatric diabetes care.

These findings support current U.S. consensus guidance on inpatient CGM use [34]. When a child is admitted with a CGM in place for more than 24 hours, crosschecking the first few CGM values against POC readings is generally sufficient before initiating clinical reliance. For newly applied sensors, clinical care teams should expect higher day-1 variability (MARD>11%) and maintain routine fingerstick frequency or confirm hypoglycemia alarms until days 2–3, particularly in the context of hypoglycemia alarms or when making critical dosing decisions [28]. Safety can be enhanced by setting slightly higher low-glucose alarm thresholds (e.g., 80 mg/dL) and accounting for the physiological lag time (5–15 minutes) between interstitial and plasma glucose. In the ICU setting, CGM use remains feasible once perfusion stabilizes; however, confirmatory POC testing is warranted when CGM values would prompt substantial insulin adjustments or when sensor signal quality is suboptimal [28,29]. Broader adoption of inpatient CGM will require robust integration with electronic medical records, remote monitoring dashboards, standardized calibration and removal protocols, and comprehensive staff education to interpret trend arrows and rate-ofchange alarms [34,35].

This study offers several advantages that enhance its contribution to the field. First, it represents the largest analysis to date that focuses exclusively on hospitalized children and adolescents with T1DM in Asia, an understudied population in CGM accuracy research. Second, each POC glucose value was matched to the nearest CGM reading using linear interpolation, minimizing timing bias and better approximating real-world clinical decision-making compared with prior reports. Third, by encompassing the full spectrum of inpatient care, including ICU admissions, and stratifying results by sensor day and glucose range, we captured CGM performance across the most clinically relevant scenarios. Fourth, using multiple accuracy metrics (MARD, MAD, Clarke error grid, and Bland-Altman) combined with linear mixed-effects modeling allowed a comprehensive assessment that accounted for repeated measures within patients. Finally, the 11-day observation period delineated the complete trajectory of accuracy maturation for both the G6 and G7 devices, thereby defining the practical "time-to-trust" threshold for each. Collectively, these strengths provide a robust and clinically actionable evidence base to inform best-practice guidelines and guide future multicenter investigations on inpatient CGM use in pediatric patients with T1D.

Several limitations warrant consideration. First, the retrospective, single-center design and exclusive inclusion of patients with T1DM limit the generalizability of the findings to other dysglycemic populations. Moreover, the performance of other non-Dexcom devices has yet to be evaluated. Second, because the reference standard was POC capillary meters, with an inherent analytical error of ±15% [20,27], the degree of sensor inaccuracy observed in this study may have been overestimated. Finally, potential selection bias must also be acknowledged, given that the continuation of CGM use was subject to individual clinician judgment.

Future work should involve multicenter prospective trials to confirm accuracy across varied clinical environments and determine whether CGM-guided protocols increase time-in-range, decrease the incidence of hypoglycemia, improve insulin-dose precision, and shorten hospital stay. Workflow investigations should examine the integration of automated data feeds, central alarm monitoring, diabetes nurse educators' training requirements, and cost-effectiveness. Hybrid closed-loop pumps may offer the prospect of semiautomated insulin delivery during routine admissions or recovery from DKA. Incremental sensor improvements, including shorter warm-up periods, enhanced accuracy in the hypoglycemic range, and extended wear times, are expected to further reduce implementation barriers. Our findings indicate that the current sixth- and seventh-generation Dexcom systems already provide reliable, near-real-time glucose data in hospitalized children, provided that clinical teams respect the brief break-in intervals and continue to verify outlier readings judiciously. As professional societies refine clinical guidance and regulatory frameworks, inpatient CGM is poised to become the standard of care for pediatric patients with T1DM, enabling safer, less intrusive, and more precise glycemic management.

In conclusion, Dexcom G6 and G7 sensors rapidly achieved inpatient benchmarks in pediatric inpatients with T1D. The G7 achieved a MARD below 10% by day 4, and the G6 by day 6. By day 4, over 94% of CGM-POC glucose pairs fell within Clarke error grid zones A + B, with Bland-Altman LoAs of ±35 mg/dL. These results satisfied both the ISO 15197:2013 and FDA iCGM accuracy criteria. While modest reductions in accuracy were observed in ICUs and during hypoglycemia, these findings support confirmatory POC testing during the first 48–72 hours of sensor wear and in response to lowglucose alarms. Overall, the results support the routine inpatient use of modern Dexcom CGMs following a brief initial stabilization period.