Credits Earned (2024) Crédits obtenus

Redeem Prepaid Membership

Tools for Practice Outils pour la pratique


#68 Hemoglobin A1c for the Diagnosis of Type 2 Diabetes


CLINICAL QUESTION
QUESTION CLINIQUE
What are the advantages and disadvantages of using hemoglobin A1c (A1c) as a diagnostic test for Type 2 diabetes mellitus?


BOTTOM LINE
RÉSULTAT FINAL
Hemoglobin A1c can be used to diagnose diabetes. Controversy remains around the best cut-off, but ≥6.5% is most commonly recommendedDifferent tests to diagnosis diabetes (A1c, fasting plasma glucose, and oral glucose tolerance tests) may give inconsistent results, so it is recommended the same test be used for retesting to confirm a diagnosis. 



CFPCLearn Logo

Reading Tools for Practice Article can earn you MainPro+ Credits

La lecture d'articles d'outils de pratique peut vous permettre de gagner des crédits MainPro+

Join Now S’inscrire maintenant

Already a CFPCLearn Member? Log in

Déjà abonné à CMFCApprendre? Ouvrir une session



EVIDENCE
DONNÉES PROBANTES
Nsingle test represents a gold-standard to diagnose diabetes.1   Agreement between A1c, fasting plasma glucose (FPG), and oral glucose tolerance testing (OGTT) is poor.2 
  • A1c >6.5% misses 47% of cases of diabetes diagnosed by FPG (>7 mmol/L) and 63% of diabetes by OGTT (>11.1 mmol/L). 
    • In some studies, A1c diagnosed more diabetes than OGTT.3-5 
  • Notably, FPG also misses 46% of diabetes diagnosed by OGTT. 
Predicting complications of diabetes: 
  • Microvascular: A1c as good as FPG or OGTT.6,7 
  • Macrovascular: A1c better than FPG,8,9 and similar to OGTT.8 
Diagnostic cut-off of >6.5%. 
  • Best cut-off for prediction of complications varied from >5.8 to >7.3%.6-9 
    • Cut-off for black individuals (>5.5%)10 may be lower than Asian or white patients. 
  • Lower A1c improves sensitivity, but decreases specificity. 
    • Example: Sensitivity (compared to FPG) improved from 53% to 73% when decreasing the threshold from >6.5% to >6.1%.2 
Context:  
  • All major guidelines11-13 now include A1c >6.5% in the diagnostic criteria for diabetes. 
    • Positive results (FPG, OGTT or A1c) should be confirmed by presence of symptomatic hyperglycemia, or by repeating the same test on a different day.11 
  • Although previously the preferred diagnostic test for diabetes, FPG: 
    • Requires patient compliance with fasting. 
    • Has high variability within the same individual.11,14 
  • Other considerations for A1c: 
    • Does not require fasting and has less variability in the same individual than FPG.14 
    • More expensive. 
    • Not reliable in certain medical conditions (e.g. anemia, hemoglobinopathies).15 
july 27 2016- Ricky D. Turgeon BSc(Pharm) ACPR PharmD


Latest Tools for Practice
Derniers outils pour la pratique

#374 Vitamin D and Fracture Prevention: Not what it’s cracked up to be?

Does vitamin D prevent fragility fractures?
Read Lire 0.25 credits available Crédits disponibles

#373 Strategies for initiating insulin in type 2 diabetes

What is the optimal initial insulin for patients with type 2 diabetes?
Read Lire 0.25 credits available Crédits disponibles

#372 Mission Slimpossible Part 2: Oral GLP-1 agonists for weight loss

Are oral GLP-1 agonists effective for weight loss?
Read Lire 0.25 credits available Crédits disponibles

This content is certified for MainPro+ Credits, log in to access

Ce contenu est certifié pour les crédits MainPro+, Ouvrir une session


Author(s)
Auteur(s)
  • G. Michael Allan MD CCFP
  • Marco Mannarino MD CCFP

1. The International Expert Committee. Diabetes Care. 2009; 32:1327-34.

2. NCD Risk Factor Collaboration (NCD-RisC). Lancet Diabetes Endocrinol. 2015; 3:624-37.

3. Bernal-Lopez MR, Santamaría-Fernandez S, Lopez-Carmona D, et al. Diabetic Med. 2011; 28:1319-22.

4. Cosson E, Nguyen MT, Hamo-Tchatchouang E, et al. Diabetic Med. 2011; 28:567-74.

5. Mostafa SA, Davies MJ, Webb D, et al. Diabetic Med. 2010; 27:762-9.

6. Colagiuri S, Lee CM, Wong TY, et al. Diabetes Care. 2011; 34:145-50.

7. McCance DR, Hanson RL, Charles MA, et al. BMJ. 1994; 308:1323-8.

8. Cederberg H, Saukkonen T, Laakso M, et al. Diabetes Care. 2010; 33:2077-83.

9. Selvin E, Steffes MW, Zhu H, et al. N Engl J Med. 2010; 362:800-11.

10. Tsugawa Y, Mukamal KJ, Davis RB, et al. Ann Intern Med. 2012; 157:153-9.

11. Canadian Diabetes Association Clinical Practice Guidelines Expert Committee. Can J Diabetes. 2013; 37:S8-S11.

12. Chamberlain JJ, Rhinehart AS, Shaefer CF, et al. Ann Intern Med. 2016; 164:542-52.

13. Report of a World Health Organization Consultation. Diabetes Res Clin Pract. 2011; 93:299-309.

14. Selvin E, Crainiceanu CM, Brancati FL, et al. Arch Intern Med. 2007; 167:1545-51.

15. Hare MJ, Shaw JE, Zimmet PZ. J Intern Med. 2012; 271:227-36.

Authors do not have any conflicts of interest to declare.

Les auteurs n’ont aucun conflit d’intérêts à déclarer.

Most recent review: 27/07/2016

By: Ricky D. Turgeon BSc(Pharm) ACPR PharmD

Comments:

Evidence Updated: New evidence; Bottom Line: Slight change.

Learning at a glance
Yearly credits
Acquired ()
Your content by topic
Cardiology Dermatology Emergency
My Bookmarks