Generic Protocols for the Analytical Validation of Next-Generation Sequencing-Based ctDNA Assays: A Joint Consensus Recommendation of the BloodPAC's Analytical Variables Working Group.

Liquid biopsy, particularly the analysis of circulating tumor DNA (ctDNA), has demonstrated considerable promise for numerous clinical intended uses. Successful validation and commercialization of novel ctDNA tests have the potential to improve the outcomes of patients with cancer. The goal of the Blood Profiling Atlas Consortium (BloodPAC) is to accelerate the development and validation of liquid biopsy assays that will be introduced into the clinic. To accomplish this goal, the BloodPAC conducts research in the following areas: Data Collection and Analysis within the BloodPAC Data Commons; Preanalytical Variables; Analytical Variables; Patient Context Variables; and Reimbursement. In this document, the BloodPAC's Analytical Variables Working Group (AV WG) attempts to define a set of generic analytical validation protocols tailored for ctDNA-based Next-Generation Sequencing (NGS) assays. Analytical validation of ctDNA assays poses several unique challenges that primarily arise from the fact that very few tumor-derived DNA molecules may be present in circulation relative to the amount of nontumor-derived cell-free DNA (cfDNA). These challenges include the exquisite level of sensitivity and specificity needed to detect ctDNA, the potential for false negatives in detecting these rare molecules, and the increased reliance on contrived samples to attain sufficient ctDNA for analytical validation. By addressing these unique challenges, the BloodPAC hopes to expedite sponsors' presubmission discussions with the Food and Drug Administration (FDA) with the protocols presented herein. By sharing best practices with the broader community, this work may also save the time and capacity of FDA reviewers through increased efficiency.

GLYCEMIC EFFECTS OF SGLT-2 INHIBITOR CANAGLIFLOZIN IN TYPE 1 DIABETES PATIENTS USING THE DEXCOM G4 PLATINUM CGM.

OBJECTIVE: Limited information is available on chronic use of sodium glucose cotransporter 2 inhibitors in type 1 diabetes (T1D). We conducted a retrospective review of T1D patients on Dexcom G4Platinum continuous glucose monitors (DCGMs) >1 year (mean, 4.6 years) who were prescribed canagliflozin (CANA) 100 mg daily and had a baseline DCGM 30-day download prior to and a second download after at least 1 month (mean, 3.7 months) taking CANA 100 mg daily. The glycemic, weight, and systolic blood pressure (SBP) effects are reported. METHODS: We identified 27 patients meeting the selection criteria: 14 men; 25 white; 22 on pump; average T1D duration, 34 years (range, 12 to 48 years); average hemoglobin A1C (A1C), 7.6% (range, 6.1 to 9.8%); 22 with baseline A1C 7.0% or higher. All patients had an estimated glomerular filtration rate (eGFR) at baseline of 60 mL/min/1.73 m(2) or higher and were normotensive or on stable therapy. On average, 29 days of CGM data was reviewed. Total daily insulin dose (TDD) was available in 21 patients. We identified 27 patients who were judged to be candidates for CANA but did not have any change in glycemic therapy other than insulin adjustment as controls. RESULTS: CANA resulted in significant reductions in mean blood glucose, CGM standard deviation, time in hyperglycemia, A1C, weight, SBP, and TDD, with increased time in target, with minimal increase in hypoglycemia and no significant change in eGFR. Three females developed genital mycotic infections but continued therapy, 2 developed ketoacidosis from insulin interruption. CONCLUSION: CANA offers promise as adjunct therapy in T1D, though caution is advised.

Personal real-time continuous glucose monitoring in patients 65 years and older.

OBJECTIVE: Little information is available on personal real-time continuous glucose monitoring (PCGM) in patients ≥65 years old. We report on PCGM use in insulin-requiring patients ≥65 years old in a community endocrine practice. METHODS: Patients ≥65 or older who had been prescribed PCGM were identified by retrospective review. Glycated hemoglobin (A1C) values from the year prior and subsequent to PCGM prescription, the most recent A1C value, continued PCGM usage, percentage reporting severe hypoglycemia (SH), and rate of SH were examined. RESULTS: Thirty-eight patients were identified: 31 with type 1 diabetes, 21 females, mean age 70 years (range 65-78), and a mean diabetes duration of 31 years. Overall, 28 were on insulin pump therapy, 29 were using PCGM regularly, and 25 had both pre- and post-PCGM use A1C results. Regular PCGM use was associated with a decrease in mean (SD) A1C: 7.6 (0.9)% to 7.1 (0.9)%, (P<.0001) that was maintained until the most recent A1C value (7.2 [0.8]%, P = .0145, average 37 months), with fewer reporting SH (from 79% to 31%, P = .0002), and a lower rate of SH (0.37 to 0.12 per year, P = .0007). The group of 9 patients who did not continue PCGM (mean use 3 months) was too small to allow meaningful statistical evaluation. Lack of insurance coverage was the most common reason given for not using/continuing PCGM. Those continuing PCGM were more likely to have insurance coverage for PCGM (86%) than those not continuing PCGM (25%). CONCLUSIONS: Patients ≥65 with insulin-requiring diabetes achieve improved glycemic control with regular PCGM use. The presence of PCGM insurance coverage favored continued PCGM use.

Hemoglobin A1C, mean glucose, and persistence of glycation ratios in insulin-treated diabetes.

OBJECTIVE: Determine the relationship between mean glucose (MG), as assessed by continuous glucose monitoring (CGM), and hemoglobin A1c (A1C) in insulin-requiring adults in a clinical practice setting and examine the persistence of this relationship over time. METHODS: In this retrospective record review in a diabetes practice, a linear regression model was developed using data sets from all patients with ≥1 available download of a Dexcom SevenPlus CGM device in which there was >50% utilization in the 60 days prior to a laboratory A1C. Persistence of the MG to A1C relationship was examined in patients with ≥2 data sets available. RESULTS: A total of 139 patients had ≥1 data set available for evaluation, and 101 patients had ≥2 data sets (range, 2 to 6; total, 279). The slope of the MG versus A1C curve was 19.5 mg/dL for each 1% change in A1C, with an intercept of 17.7 mg/dL. Although 88% of the measured MG values were within 15% of the A1C-predicted MG, there was substantial variation in individuals, with differences as large as ±26%. The MG to A1C (MG:A1C) ratio, which is a measure of glycation, was normally distributed, with a median of 21.6. Spearman correlation coefficients for the MG:A1C ratio on repeated measures ranged from 0.52 to 0.73, demonstrating persistence. CONCLUSION: The relationship between MG and A1C is linear in a population but can vary between individuals. The MG:A1C ratio was normally distributed, tended to persist in individuals over time, and thus could be useful to identify apparent high and low glycators. Glycemic goals may need to be modified in such patients.

The Accuracy and Efficacy of the Dexcom G4 Platinum Continuous Glucose Monitoring System.

BACKGROUND: The purpose of this study was to evaluate the accuracy and efficacy of Dexcom G4 Platinum CGM System. METHODS: Seventy-two subjects enrolled at 4 US centers; 61% were male; 83% had T1DM and17% had T2DM. Subjects wore at least 1 system for up to 7 days. Subjects participated in a total of 36 hours in the clinic to contribute YSI reference glucose measurements with venous blood draws every 15 minutes on study Day 1, Day 4, and Day 7. RESULTS: The overall mean absolute relative difference (ARD) versus YSI was 13% with a median of 10%. Precision ARD was 9% ± 4% between 2 sensors with a 7% coefficient of variation. The mean ARD versus SMBG was 14% with a median of 11%. One hundred two (94%) sensors lasted 7 days and the systems displayed 97% of their expected glucose readings in average. The time spent in low CGM readings during nighttime hours decreased from the first night use to the 6th night (P < .001) with a small difference in average CGM glucose from 147 ± 40 mg/dL to 166 ± 62 mg/dL. There were no serious adverse events or infectious complications reported. CONCLUSIONS: The study showed the Dexcom G4 Platinum CGM System is one of the most accurate CGMs. The significant reduction in nocturnal time spent in a hypoglycemic state observed during this study suggests that a longer term study of CGM use, especially nocturnal use, could be beneficial for patients with hypoglycemia unawareness.

Hypoglycemic Accuracy and Improved Low Glucose Alerts of the Latest Dexcom G4 Platinum Continuous Glucose Monitoring System.

OBJECTIVE: Accuracy of continuous glucose monitoring (CGM) devices in hypoglycemia has been a widely reported shortcoming of this technology. We report the accuracy in hypoglycemia of a new version of the Dexcom (San Diego, CA) G4 Platinum CGM system (software 505) and present results regarding the optimum setting of CGM hypoglycemic alerts. MATERIALS AND METHODS: CGM values were compared with YSI analyzer (YSI Life Sciences, Yellow Springs, OH) measurements every 15 min. We reviewed the accuracy of the CGM system in the hypoglycemic range using standard metrics. We analyzed the time required for the CGM system to detect biochemical hypoglycemia (70 mg/dL) compared with the YSI with alert settings at 70 mg/dL and 80 mg/dL. We also analyzed the time between the YSI value crossing 55 mg/dL, defined as the threshold for cognitive impairment due to hypoglycemia, and when the CGM system alerted for hypoglycemia. RESULTS: The mean absolute difference for a glucose level of less than 70 mg/dL was 6 mg/dL. Ninety-six percent of CGM values were within 20 mg/dL of the YSI values between 40 and 80 mg/dL. When the CGM hypoglycemic alert was set at 80 mg/dL, the device provided an alert for biochemical hypoglycemia within 10 min in 95% of instances and at least a 10-min advance warning before the cognitive impairment threshold in 91% of instances in the study. CONCLUSIONS: Use of an 80 mg/dL threshold setting for hypoglycemic alerts on the G4 Platinum (software 505) may provide patients with timely warning of hypoglycemia before the onset of cognitive impairment, enabling them to treat themselves for hypoglycemia with fast-acting carbohydrates and prevent neuroglycopenia associated with very low glucose levels.

A new-generation continuous glucose monitoring system: improved accuracy and reliability compared with a previous-generation system.

BACKGROUND: Use of continuous glucose monitoring (CGM) systems can improve glycemic control, but widespread adoption of CGM utilization has been limited, in part because of real and perceived problems with accuracy and reliability. This study compared accuracy and performance metrics for a new-generation CGM system with those of a previous-generation device. SUBJECTS AND METHODS: Subjects were enrolled in a 7-day, open-label, multicenter pivotal study. Sensor readings were compared with venous YSI measurements (blood glucose analyzer from YSI Inc., Yellow Springs, OH) every 15 min (±5 min) during in-clinic visits. The aggregate and individual sensor accuracy and reliability of a new CGM system, the Dexcom(®) (San Diego, CA) G4™ PLATINUM (DG4P), were compared with those of the previous CGM system, the Dexcom SEVEN(®) PLUS (DSP). RESULTS: Both study design and subject characteristics were similar. The aggregate mean absolute relative difference (MARD) for DG4P was 13% compared with 16% for DSP (P<0.0001), and 82% of DG4P readings were within ± 20 mg/dL (for YSI ≤ 80 mg/dL) or 20% of YSI values (for YSI >80 mg/dL) compared with 76% for DSP (P<0.001). Ninety percent of the DG4P sensors had an individual MARD ≤ 20% compared with only 76% of DSP sensors (P=0.015). Half of DG4P sensors had a MARD less than 12.5% compared with 14% for the DSP sensors (P=0.028). The mean absolute difference for biochemical hypoglycemia (YSI <70 mg/dL) for DG4P was 11 mg/dL compared with 16 mg/dL for DSP (P<0.001). CONCLUSIONS: The performance of DG4P was significantly improved compared with that of DSP, which may increase routine clinical use of CGM and improve patient outcomes.