Impact of glucose meter accuracy on the efficacy of glycemic control in critically ill patients after

cardiovascular surgery

Brad S. Karon1 and Sandra K. Bryant2

1 Department of Laboratory Medicine and Pathology

2 Division of Biomedical Statistics and Informatics

Mayo Clinic

Rochester, MN

Disclosures

• None

2

Error simulation models—accuracy required for moderate glycemic control (MGC, target glucose 110-150 mg/dL)

3 category dosing error critical

Error simulation models--MGC

Error condition

10% TEa

% Bias/CV

10% TEa

Gaussian

15% TEa

% Bias/CV

15% TEa

Gaussian

20% TEa

% Bias/CV

20% TEa

Gaussian

1cat Up to 60%

29% Up to 80%

39% Up to 90%

83%

2 cat 0.2% 0.2% Up to 5% 2% Up to 20%

6%

≥ 3 cat 0% 0% 0% 0.02% 0.2% 0.3%

Karon et al., Diabetes Tech Ther 2013;15:996-1003

TEa = total allowable error = bias + (1.65 X CV)

Empiric validation of MGC error model

• 4017 paired glucose meter and serum glucose drawn within 5 minuteso Glucose meter ~ 20% TEa

• Empirically observed dosing errors close to those predicted by Gaussian model at 20% TEao Observed bias much less than ± 20%

• What is impact of ≥ 2 category dosing errors?

Error condition

20% TEa% bias/CV

20% TEaGaussian

Empiric data

1 cat error Up to 90% 83% 39%2 cat error Up to 20% 6% 4%≥ 3 cat error 0.2% 0.3% 0.3%

Impact of insulin dosing errors on glycemic control in ICU• Impact on patient outcome

o ICU/hospital mortalityo Hospital morbidity (infections, transfusions,

renal failure)o Requires randomized trial > 1000 patients

• Impact on glycemic control efficacyo Glycemic variabilityo Time within target rangeo Incidence hypo and hyperglycemiao Requires 50-150 patients per study arm

Study design

• Determine accuracy of two glucose meters each used in same ICU patient populationo Paired meter/serum samples collected within 5 min

• Retrospective review patients post cardiovascular surgery placed on glycemic control in CVS ICUo 12-24 consecutive (30-120 min) glucose values on

insulin drip o Period 1 (45 patients monitored with AccuChek Inform)o Period 2 (54 patients monitored with StatStrip)o No change infusion protocol, testing personnel, etco Outcome glycemic variability from consecutive

glucose values, time within target range, incidence hypo and hyperglycemia

Results—glucose meter accuracy in ICU

• 1602 paired whole blood meter vs. serum glucoseo 6 ICU areas, Aug-Oct 2012 (Period 1), Inform 1

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Results—glucose meter accuracy in ICU

• 1093 paired whole blood vs. serum glucoseo 6 ICU areas, June-Aug 2013 (Period 2), StatStrip

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Results—glucose meter accuracy in ICU

• Reduced bias, TEa from ~20% 12.5%

• Diabetes Tech Ther 2014; DOI: 10.1089/dia.2014.0074

Period 1 Period 2Median (IQR) bias (mg/dL) 11 (6 - 18 ) mg/dL 1 (-5 - 5) mg/dL% within 20%/15 mg/dLserum

92% 98%

% within 15%/15 mg/dL(NACB) serum

80% 97%

% within 12.5%/12.5 mg/dL(CLSI POCT12-A3) serum

69% 95%

Study design

• Measures glycemic variabilityo Standard deviation (SD)o Continuous overall net glycemic action (CONGA)

Patient demographics Period 1(9-11/2012)

Period 2 (12/13-3/14)

P value

Mean ± SD age (range) 66 ± 13 (28-85) 64 ± 12 (29-86) 0.6237Gender 27 M/ 18 F 35 M/ 19 FDiabetes 24 ND/ 21 D2 29 ND/ 25 D2Median (range) number glucose values

21 (12-24) 22 (12-24) 0.14

Median (IQR) glucose value (mg/dL)

142 (126-158) 137 (125-149) 0.01

Median (IQR) value ND 134 (120-150) 134 (122-145) 0.16Median (IQR) value D2 148 (133-166) 141 (129-153) 0.02

Results—Glycemic variability and time within target range

Period 1 (n=45) Period 2 (n=54) P valueMedian (IQR) standarddeviation (SD)

22.4 (16.4-29.3) mg/dL

15.4 (12.2-19.8) mg/dL

< 0.0001

Median (IQR) CONGA

20.5 (16.0-25.6) mg/dL

12.1 (9.9-17.4) mg/dL

< 0.0001

Median (IQR) time in target range (%)

62.5 (46.7-72.5) % 71.1 (61.1-84.6) % 0.003

• Overall results (non-diabetic and diabetic type 2)

Results—Glycemic variability and time within target range

• Results, non-diabetic patients only

Period 1 (n=24) Period 2 (n=29) P valueMedian (IQR) standarddeviation (SD)

19.4 (16.1-28.7) mg/dL

15.4 (12.2-19.8) mg/dL

0.01

Median (IQR) CONGA

18.8 (14.2-24.3) mg/dL

12.8 (10.2-18.9) mg/dL

0.006

Median (IQR) time in target range (%)

65.8 (50.0-72.7) % 73.7 (62.5-88.6) % 0.03

Results—Incidence of hypo and hyperglycemia

• Hypoglycemia (< 70 mg/dL), non-diabetic patients• 1 patient, 1 value Period 1• 0 patients, 0 values Period 2

• Hyperglycemia (> 200 mg/dL), non-diabetic patients• 6 patients, 13 values Period 1• 1 patient, 2 values Period 2

Conclusions

• Glucose meter bias decreased between Period 1 (Inform) and Period 2 (StatStrip) in ICU patients

• Reduced glucose meter bias likely improved efficacy of glycemic control after cardiovascular surgeryo Glycemic variability decreased (SD and CONGA)o Time within target range (110-150 mg/dL) increasedo Fewer episodes hyperglycemia (> 200 mg/dL) observed

• Data on diabetic patients confounded by intraoperative glycemic control during Period 2