Use of the
                   Estimated Average
                   Glucose (eAG) in
                   Patient Care



www...
A Typical Patient Encounter
   “So, Mrs. Smith, it looks like
   you do have diabetes. Your
   repeat fasting blood sugar ...
A Typical Patient Encounter
  “What’s a hemoglobin A…
   whatever you said? I
   remember my hemoglobin
   was low when I ...
G          G       G                 G
     G                     G
             G
                   G
                  ...
Uh…


                   ???




www.diabetes.org         1-800-DIABETES
It’s Not Just Confusing for
       Newly Diagnosed Patients
    • High levels of testing of HbA1c for
      patients with ...
The Clinical Dilemma
 • HbA1c: useful for research, risk
   prediction, target of therapy
 • Well standardized
 • HOWEVER,...
The Concept of Average Glucose
 • We tell patients the HbA1c reflects their
   “average glucose over 2-3 months”

 • But: ...
Study      Year    Cohort     Study period       Number of
                                  (weeks)         glucose tests...
The A1C-Derived Average Glucose
         (ADAG) Study
International study designed to:
• Carefully look at relationship be...
ADAG Study Centers
    • Cameroon          • United States
    • Denmark              –   Boston
                         ...
Participants in ADAG
    • Goal was to recruit people with
        – Type 1 diabetes
        – Type 2 diabetes
        – N...
Measures of Glycemia in ADAG Study
 • CGM (calibrated by 8-point glucose profiles with
   Hemocue meter) for at least 48 h...
ADAG Study Flow

 Total Enrolled                  661

  Eliminated from analysis       154 (23%)

   - Dropped out or exc...
Baseline Characteristics of ADAG
                  Participants
                        Type 1     Type 2     Non-DM      ...
ADAG Study: Distribution of Baseline
                   HbA1c
        400
        350
Number 300
                         ...
ADAG Study: Glucose Monitoring
• CGM – mean of ~ 2,400 measurements per
  participant
• LifeScan meter ~ mean of 300 measu...
ADAG Study: Analyses
• CGM results corrected upward by 5% to be
  consistent with BG
• Each glucose measure weighted in pr...
ADAG Study: Study Success
          18

          16
                                                        90% of
      ...
ADAG Study: Correlation of AG
                     With HbA1c

                 AG (mg/dl) = 28.7 x HbA1c – 46.7
         ...
ADAG Study: Correlation of AG
                             with HbA1c: CGM data vs. Meter
                    18
         ...
ADAG Study: Other Factors Examined
• Does the HbA1c-Average Glucose relationship
  differ by:
    - Type 1 or type 2 diabe...
ADAG Study Excluded Known Sources
     of “Inaccuracy” of HbA1c
            •   Hemoglobinopathy
            •   Anemia
  ...
ADAG Study Conclusion:
       HbA1c Correlates Highly With AG
             450
             400
             350   AG (mg/...
Implications
• Tight correlation between HbA1c and AG
  allows us to translate HbA1c into an
  estimated Average Glucose (...
ADAG Study: “Translation” of
        HbA1c into eAG
                        eAG
    HbA1c (%)      (mg/dl)  (mmol/l)_
    ...
Note that the numbers are different

                   ADAG      DCCT
    HbA1c (%)      (mg/dl)___(mg/dl)______
      6 ...
Consensus Statement FCC, EASD, IDF, ADA
               Sept 2007)

 • HbA1c assay to be standardized
   worldwide using th...
What Won’t Change…And What’s New

• To a clinician, there is no change in the
  HbA1c assay
• To clinical chemists, there ...
A Typical Patient Encounter
  “So, Mrs. Smith, it looks like you do
   have diabetes. Your average blood
   sugar is aroun...
A Typical Patient Encounter
   “Wow, I’m not happy to hear
   that…I know that diabetes
   can do some bad things. Tell
  ...
What is ADA Doing to Promote
     Use of eAG in Patient Care?
     • Health care provider education
         –   ADA Scien...
What Can Clinicians and
          Educators Do?
 • Choose which term—A1C or Average Glucose—
   to use with each patient (...
What Can Clinical Chemists Do?
• Even with tools, most clinicians will not take the
  time to calculate conversions
• Repo...
Average Glucose
                          Blood pressure
                          Cholesterol




                   to h...
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eAG - Estimated Average Glucose

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eAG - Estimated Average Glucose

  1. 1. Use of the Estimated Average Glucose (eAG) in Patient Care www.diabetes.org 1-800-DIABETES
  2. 2. A Typical Patient Encounter “So, Mrs. Smith, it looks like you do have diabetes. Your repeat fasting blood sugar was 178, and as you recall the first one was 187. Over 126 is diabetes. Also, your hemoglobin A1c was way too high at 8.6%. Normal is less than 6%. We need to get it below 7%.” www.diabetes.org 1-800-DIABETES
  3. 3. A Typical Patient Encounter “What’s a hemoglobin A… whatever you said? I remember my hemoglobin was low when I was pregnant. What were those other numbers? What do you mean, 7%...of what?” www.diabetes.org 1-800-DIABETES
  4. 4. G G G G G G G G G G G G ÷ G = __% GG www.diabetes.org 1-800-DIABETES
  5. 5. Uh… ??? www.diabetes.org 1-800-DIABETES
  6. 6. It’s Not Just Confusing for Newly Diagnosed Patients • High levels of testing of HbA1c for patients with known diabetes (> 90%). • Of patients with test in past 6 months: – 66% did not know result – 25% accurately reported within 1% range (< 7%, 7-8%, 8-9%) – 9% inaccurately reported within 1% range Heisler, Diabetes Care 28:816,2005 www.diabetes.org 1-800-DIABETES
  7. 7. The Clinical Dilemma • HbA1c: useful for research, risk prediction, target of therapy • Well standardized • HOWEVER, difficult to explain to patients • Concept of % is not intuitive • Glucose more familiar to patients from self-monitoring or from laboratory glucose results www.diabetes.org 1-800-DIABETES
  8. 8. The Concept of Average Glucose • We tell patients the HbA1c reflects their “average glucose over 2-3 months” • But: do we know this for sure? www.diabetes.org 1-800-DIABETES
  9. 9. Study Year Cohort Study period Number of (weeks) glucose tests per patient per 1-3 months Svendsen 1982 15 T1DM 5 200-300 Nathan 1984 21 T1DM 8 200-300 DCCT 2002 1439 T1DM 12 7 Hempe 2002 128 T1DM 4 80 Murata 2004 182 T2DM 8 180 Nathan 2007 22 T1DM 12 24,000 3 Normals (CGMS) www.diabetes.org 1-800-DIABETES
  10. 10. The A1C-Derived Average Glucose (ADAG) Study International study designed to: • Carefully look at relationship between HbA1c and average glucose • Determine the mathematical relationship between the two for reliable conversion • Establish that the relationship is valid across: - Diabetes types - A wide range of HbA1c levels and age - Different races/ethnicities Nathan et al, Diabetes Care 31:1473, 2008 www.diabetes.org 1-800-DIABETES
  11. 11. ADAG Study Centers • Cameroon • United States • Denmark – Boston – New York • Italy – San Antonio – Seattle • The Netherlands • India (site dropped due to specimen handling issues) www.diabetes.org 1-800-DIABETES
  12. 12. Participants in ADAG • Goal was to recruit people with – Type 1 diabetes – Type 2 diabetes – No diabetes • With a range of – Ethnicity/race – HbA1c levels • Excluded those with conditions that would interfere with measurement/interpretation of HbA1c or glucose www.diabetes.org 1-800-DIABETES
  13. 13. Measures of Glycemia in ADAG Study • CGM (calibrated by 8-point glucose profiles with Hemocue meter) for at least 48 hours at baseline and every month for 3 months • 7-point glucose profiles for 3 days per week with One Touch Ultra meter • HbA1c at baseline and monthly X 3 months with DCCT-aligned assay in a central laboratory • Four measures of HbA1c to assure stable control, but only final value used for correlation with prior 3 months’ glucose readings www.diabetes.org 1-800-DIABETES
  14. 14. ADAG Study Flow Total Enrolled 661 Eliminated from analysis 154 (23%) - Dropped out or excluded 91 (14%) during study - Inadequate CGM 11 (2%) - Inadequate HbA1c samples 52 (8%) www.diabetes.org 1-800-DIABETES
  15. 15. Baseline Characteristics of ADAG Participants Type 1 Type 2 Non-DM Total Number 268 159 80 507 Age 43 + 13 56 + 9 40 + 14 46 + 14 Gender (% F) 52% 50% 69% 54% Race/Ethnicity White 93% 73% 71% 83% African/Af-Am 2% (5) 13% (21) 15% (12) 8% (38) Hispanic 6% (15) 8% (12) 15% (12) 8% (39) Treatment Pump / ≥3 inject/day 47% / 53% Diet only/ 10% Oral agent only 52% Insulin only 19% Insulin & oral 19% www.diabetes.org 1-800-DIABETES
  16. 16. ADAG Study: Distribution of Baseline HbA1c 400 350 Number 300 44% of 38% 250 subjects Normal 200 150 D i 18% a 100 b e 50 t i 0 c 4-6.5 6.6-8.5 >8.5 Baseline HbA1c (%) www.diabetes.org 1-800-DIABETES
  17. 17. ADAG Study: Glucose Monitoring • CGM – mean of ~ 2,400 measurements per participant • LifeScan meter ~ mean of 300 measurements per participant – Mean of ~ 25 measurements per week – Goal was a minimum of 21 tests per week • Total ~ 2,700 measurements/participant during 12 weeks www.diabetes.org 1-800-DIABETES
  18. 18. ADAG Study: Analyses • CGM results corrected upward by 5% to be consistent with BG • Each glucose measure weighted in proportion to the inverse of total number of measurements on that day (each day had equal weight) • Arithmetic mean glucose calculated for each participant • Linear regression model used to estimate relationship between average glucose and the 3-month HbA1c www.diabetes.org 1-800-DIABETES
  19. 19. ADAG Study: Study Success 18 16 90% of 14 cohort values Calc. AG (mmol/ 12 fall in this range 10 8 6 4 L) 2 0 HbA1c (%) 90% of values fell within +/- 15% www.diabetes.org 1-800-DIABETES
  20. 20. ADAG Study: Correlation of AG With HbA1c AG (mg/dl) = 28.7 x HbA1c – 46.7 R2 = 0.84 AG (mg/dl) P < 0.0001 HbA1c (%) www.diabetes.org 1-800-DIABETES
  21. 21. ADAG Study: Correlation of AG with HbA1c: CGM data vs. Meter 18 CGM calc. AG = 1.649x - 2.645 16 2 R = 0.768 14 Calc. AG (mmol/L) 12 10 No difference in 8 relationship (P=0.18) whether LifeScan or 6 CGMS data used Lifescan calc. AG = 1.574x HbA1c- 2.547 4 R2 = 0.802 2 0 3 4 5 6 7 8 9 10 11 12 13 HbA1c (%) www.diabetes.org 1-800-DIABETES
  22. 22. ADAG Study: Other Factors Examined • Does the HbA1c-Average Glucose relationship differ by: - Type 1 or type 2 diabetes NO - Diabetes or no diabetes NO - Amount of glucose variability NO - Gender NO - Age NO - Ethnicity/Race NO (but trend toward higher HbA1c per AG in African and African-American participants vs. whites, P=0.07) - Smoking NO www.diabetes.org 1-800-DIABETES
  23. 23. ADAG Study Excluded Known Sources of “Inaccuracy” of HbA1c • Hemoglobinopathy • Anemia • Pregnancy • Hepatic or renal disease • Etc. www.diabetes.org 1-800-DIABETES
  24. 24. ADAG Study Conclusion: HbA1c Correlates Highly With AG 450 400 350 AG (mg/dl) = 28.7 x HbA1c – 46.7 AG (mg/dl) 300 250 200 150 100 50 3 4 5 6 7 8 9 10 11 12 13 Measured HbA1c (%) www.diabetes.org 1-800-DIABETES
  25. 25. Implications • Tight correlation between HbA1c and AG allows us to translate HbA1c into an estimated Average Glucose (eAG) • eAG will apply to the majority of patients with diabetes – Barring “traditional” conditions interfering with the assay or the relationship between glycemia and HbA1c www.diabetes.org 1-800-DIABETES
  26. 26. ADAG Study: “Translation” of HbA1c into eAG eAG HbA1c (%) (mg/dl) (mmol/l)_ 5 97 5.4 6 126 7.0 7 154 8.6 8 183 10.2 9 212 11.8 10 240 13.4 www.diabetes.org 1-800-DIABETES
  27. 27. Note that the numbers are different ADAG DCCT HbA1c (%) (mg/dl)___(mg/dl)______ 6 126 135 7 154 170 8 183 205 9 212 240 10 240 275 www.diabetes.org 1-800-DIABETES
  28. 28. Consensus Statement FCC, EASD, IDF, ADA Sept 2007) • HbA1c assay to be standardized worldwide using the new IFCC standard and expressed as: – % as currently used (DCCT values) – IFCC units in mmol HBA1c/mol HbA – eAG in mmol/l or mg/dL (if ADAG study meets its data acceptability goals) • This paved the way for reporting both HbA1c and EAG on lab reports Diabetes Care and Diabetologia, 2007 www.diabetes.org 1-800-DIABETES
  29. 29. What Won’t Change…And What’s New • To a clinician, there is no change in the HbA1c assay • To clinical chemists, there is a new IFCC standard in the background • We have the potential for a valuable educational tool for patients www.diabetes.org 1-800-DIABETES
  30. 30. A Typical Patient Encounter “So, Mrs. Smith, it looks like you do have diabetes. Your average blood sugar is around 200. When people don’t have diabetes, this number is below 125. We need to work with you to try to get this number, the average glucose, down below 150 over the next few months with some weight loss, exercise, and a medication. Let’s talk some more about what you can do…” www.diabetes.org 1-800-DIABETES
  31. 31. A Typical Patient Encounter “Wow, I’m not happy to hear that…I know that diabetes can do some bad things. Tell me what I can do to get my average glucose down.” www.diabetes.org 1-800-DIABETES
  32. 32. What is ADA Doing to Promote Use of eAG in Patient Care? • Health care provider education – ADA Scientific Sessions, June ’08 – American Association of Clinical Chemists, August ‘08 – AADE Annual Meeting, August ‘08 – eAG calculators (handheld and on professional.diabetes.org) • Patient education – Website – Diabetes Forecast magazine, books – Pamphlets and brochures – ADA will include term “average glucose” in all consumer pieces www.diabetes.org 1-800-DIABETES
  33. 33. What Can Clinicians and Educators Do? • Choose which term—A1C or Average Glucose— to use with each patient (some may already be used to A1C) • In verbal communications, no need to say “estimated” • We want to keep the A in A,B,Cs • Use updated table, calculator on www.diabetes.org, or other tools to convert A1C to average glucose • “Lobby” your lab to report both numbers www.diabetes.org 1-800-DIABETES
  34. 34. What Can Clinical Chemists Do? • Even with tools, most clinicians will not take the time to calculate conversions • Reporting both HbA1c (DCCT-aligned) AND eAG on lab reports will do the most to promote wide use of the term • Professional and patient education may drive demand • Conversion is a simple regression equation www.diabetes.org 1-800-DIABETES
  35. 35. Average Glucose Blood pressure Cholesterol to help make the “A” understandable! www.diabetes.org 1-800-DIABETES

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