Continuous glucose monitoring accuracy results vary between assessment at home and assessment at the clinical research center.
BACKGROUND
Continuous glucose monitoring system (CGMS) accuracy is of critical importance both in delivering therapeutic value and as a component of a closed-loop system. This study aims at assessing the differences between accuracy assessments of CGMS at home and at the clinical research center (CRC).


METHODS
Twelve patients with type 1 diabetes used the Dexcom® SEVEN® PLUS (DexCom, Inc.) CGMS for 7 days. Patients performed ≥6 finger pricks [self-measurement of blood glucose (SMBG)] per day while at home. Reference blood glucose measurements were taken during a 24 h CRC admission (YSI 2300 STAT Plus™). Continuous glucose monitoring system data were compared with YSI and SMBG values. Outcome measures included mean absolute relative difference (MARD) and Clarke error grid analysis (CEGA).


RESULTS
During CRC admission, the MARD of CGMS vs YSI glucose values was 19.2% (n = 509)--significantly higher than 16.8% at home (n = 611) (p = .004). In the hypoglycemic range, MARD was 23.9% at CRC (n = 26)--not significantly different from 41.6% at home (n = 39) (p = .269). In the hyperglycemic range, CRC MARD at 20.3% (n = 115) was significantly higher than home MARD at 11.2% (n = 118) (p = .001). Clarke error grid analysis showed no significant difference in distribution of data pairs (overall p = .317).


CONCLUSIONS
This study illustrates the importance of the setting used when assessing CGMS accuracy. Continuous glucose monitoring system accuracy at home appeared better than at the CRC. This is probably due to the higher sampling rate of reference measurements, feasible only in the CRC. Testing CGMS accuracy in the CRC provides valuable information over and above home testing.
Department of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands. y.m.luijf@amc.nl
Yoeri M
YM
Luijf
Angelo
A
Avogaro
Carsten
C
Benesch
Daniela
D
Bruttomesso
Claudio
C
Cobelli
Martin
M
Ellmerer
Lutz
L
Heinemann
Julia K
JK
Mader
J Hans
JH
DeVries
D000328:Adult; D035843:Biomedical Research; D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000379:methods / Q000592:standards; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D005260:Female; D006801:Humans; D007755:Laboratories, Hospital; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D010343:Patient Admission; D015203:Reproducibility of Results; D012111:Residence Characteristics; D012648:Self Care / Q000592:standards / Q000706:statistics & numerical data; D055815:Young Adult
D001786:Blood Glucose