Table 2.
CGMS Accuracy Statistics Assessed from Laboratory Reference Values by Number of Calibrations Retrospectively Entered
|
Differenceamedian (mg/dL) |
Relative Absolute Differenceb(RAD)median |
ISO Criteriacpercentage |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Number of Calibrations | Number of Calibrations | Number of Calibrations | |||||||||||
| N | 3d | 4e | 5f | 7g | 3d | 4e | 5f | 7g | 3d | 4e | 5f | 7g | |
| During Exercise | 153 | +6 | +5 | +7 | +11 | 19% | 15% | 16% | 15% | 56% | 63% | 63% | 65% |
| Excluding Exercise | 944 | −4 | −7 | −5 | −5 | 14% | 15% | 13% | 13% | 66% | 67% | 71% | 72% |
| Reference Glucoseh | |||||||||||||
| ≤70 | 139 | +11 | +8 | +9 | +9 | 24% | 19% | 19% | 17% | 56% | 65% | 63% | 71% |
| 71–120 | 346 | −2 | −5 | −3 | −4 | 14% | 15% | 12% | 13% | 64% | 65% | 71% | 72% |
| 121–180 | 217 | −11 | −17 | −16 | −16 | 12% | 14% | 13% | 12% | 73% | 70% | 74% | 74% |
| 181–240 | 140 | −14 | −19 | −17 | −19 | 13% | 14% | 13% | 13% | 65% | 67% | 67% | 71% |
| >240 | 102 | −15 | −17 | −12 | −9 | 10% | 12% | 10% | 10% | 76% | 69% | 75% | 77% |
| Time of Dayh | |||||||||||||
| Daytime (9 a.m.–10 p.m.) | 139 | +2 | +4 | +8 | +11 | 21% | 17% | 17% | 17% | 54% | 65% | 63% | 63% |
| Overnight (10 p.m.–6 a.m.) | 805 | −5 | −9 | −8 | −8 | 13% | 15% | 13% | 12% | 69% | 67% | 72% | 74% |
| 10 p.m.–1 a.m. | 276 | −1 | −5 | −2 | −4 | 15% | 15% | 13% | 12% | 64% | 66% | 74% | 72% |
| 2 a.m.– 4 a.m. | 266 | −3 | −8 | −7 | −8 | 14% | 15% | 13% | 12% | 67% | 65% | 69% | 72% |
| 5 a.m – 6 a.m | 263 | −10 | −14 | −14 | −11 | 12% | 14% | 14% | 12% | 75% | 70% | 73% | 78% |
| Rate of Changehi | |||||||||||||
| <0.5 mg/dL/min | 190j | −7 | −9 | −7 | −9 | 13% | 13% | 11% | 13% | 66% | 69% | 73% | 74% |
| 0.5 – <1.0 mg/dL/min | 433j | −5 | −8 | −4 | −4 | 12% | 14% | 13% | 11% | 71% | 71% | 69% | 74% |
| 1.0 – <1.5 mg/dL/min | 198j | −4 | −6 | −3 | −3 | 15% | 17% | 14% | 13% | 64% | 60% | 72% | 68% |
| ≥1.5 mg/dL/min | 123j | +6 | +13 | 0 | +12 | 18% | 19% | 17% | 14% | 58% | 58% | 62% | 70% |
– Defined as the CGMS value minus laboratory reference value.
– Defined as absolute value of the difference divided by the reference (expressed as a percentage).
– ISO criteria defined as CGMS within ±15mg/dL of reference when reference ≤75mg/dL or within ±20% when reference >75mg/dL.
– 3 values used for calibrations: Ultra measurements from pre-lunch, 9 p.m. and 6 a.m.
– 4 values used for calibrations: Above 3 plus pre-dinner.
– 5 values used for calibrations: Above 4 plus midnight.
– 7 values used for calibrations: Above 5 plus 3 p.m. and 3 a.m.
– Excludes exercise session.
– Absolute rate of change at each calibration entry averaged over visit.
– Because the rate of change is calculated by the CGMS, the number of pairs in each group varies slightly by the number of calibrations. Numbers given for the 4-calibration scenario.