The A1C Prandial Product: An objective tool to decision making in diabetes.
This brief article describes a numerical index designed to assess the relative contribution of fasting and postprandial glucose to hyperglycaemia. This helps plan appropriate insulin and oral glucose-lowering therapy in an objective manner. It also reviews three similar indices described earlier in literature. Such indices need to be validated in large, multicentric trials, and have the potential to bring objectivity to choice of treatment of diabetes.
Keywords: Diabetes, insulin, oral hypoglycaemic agents, basal insulin, prandial insulin, postprandial hyperglycaemia.
Physicians often find it a challenge to decide the appropriate insulin for initiation of therapy in a given person. While the American Diabetes Association-European Association for Study of Diabetes (ADA-EASD) recommendations suggest based insulin as the initial treatment of choice, this does not take various clinical aspects (such as presence of metabolic, medical, or surgical co morbidities) or biochemical factors(such as relative contribution of fasting and postprandial glycaemia, as well as severity of glycaemia) into account.1
The International Diabetes Federation (IDF) and American Association of Clinical Endocrinologists (AACE) offer the option of initiating therapy with premixed insulin, but do not provide objective guidance regarding how to choose appropriate insulin.2,3 Usually, the choice of insulin regime or preparation is based upon a combination of subjective parameters, including physician preference and patient acceptance.4 Similar challenges are faced while prescribing oral glucose-lowering therapy.
Objective Aids to Decision
Recently, three numerical aids to decision-making have been crafted using three easily available glycaemic indices: fasting glucose (FPG), postprandial glucose (PPG), and glycosylated haemoglobin (HbA1c).5 These indices aim to assess the relative contribution of fasting and post prandial glucose to overall glycaemia, and suggest appropriate treatment strategies based upon simple calculation.
The three indices are:
1. Post prandial glucose excursion =PPGE=PPG-FPG
2. Prandial fasting index(PFI)= PPGE/FPG
3. FPG / HbA1c
The APP Index
We propose a fourth index, termed as the A1c Prandial Product (APP)
A1c Prandial Product (APP) = HbA1c x PFI
= HbA1c x (PPG-FPG)/FPG
This index provides an idea of the contribution of postprandial glucose to overall glycaemic load. Let us illustrate all four indices with two simple examples, both pertaining to persons with an HbA1c of 10.0%.
Example 1: Predominant fasting glycaemia
If FPG= 200mg% and PPG=240mg%, PPGE = 240-200=40mg%
PFI= 240-200 = 40/200 = 0.2
FPG / HbA1c= 200 /10 =20
APP=10x 0.2= 2
Example 2: Predominant postprandial glycaemia
If FPG= 150mg% and PPG=300mg%,
PFI = 300-150 = 150/150 = 1.0
FPG / HbA1c = 150/ 10 = 15
APP=10x1.0 = 10
Assessment and Cut-Offs
High PPGE, PFI, and APP suggest a higher postprandial glycaemic burden, while a higher FPG / HbA1c index implies greater contribution of fasting hyperglycaemia.
The cut-offs proposed for earlier indices have been derived from standard diagnostic cut-offs of plasma glucose for prediabetes (100 mg%, 140 mg%) and diabetes (126 mg%, 200 mg%). If similar standards are used for the APP, using a convenient HbA1c value of 6%, we get the following values:
APP = 6.0x (140-100)/100 = 6.0 x 0.4 = 2.4
APP = 6.0 X (200-126)/126 = 6.0 x 0.6 =3.5
The APP is not a validated index, and the cut-offs suggested (less than 2.4 implies predominant fasting glycaemia; >3.5 implies predominant postprandial glycaemia) are arbitrary. However, the index does provide practitioners a simple method to assess relative contributions to hyperglycaemia, and decide appropriate therapeutic strategies based upon this.
While more research is needed to determine exact cut offs and utility of the APP, and other indices, these serve as valuable tools in primary care diabetology. They help assess relative importance of pathophysiologic and glycaemic abnormalities, and facilitate crafting of appropriate glucose-lowering strategies.
1. Inzucchi S, Bergenstal R, Buse J, Diamant M, Ferrannini E, Nauck M, et al. Management of Hyperglycemia in Type 2 Diabetes, 2015: A PatientCentered Approach Update to a Position Statement of the American Diabetes Association and the European Association for the Study of Diabetes. Diabetes Care 2015; 38: 140-9.
2. Garber A, Abrahamson M, Barzilay JI, Blonde L, Bloomgarden Z, Bush M, et al. AACE comprehensive diabetes management algorithm 2013. Endocr Pract. 2015; 21: e1 - e10.
3. International Diabetes Federation Global Guideline for Diabetes management. Available at: https://www.idf.org/sites/default/files/IDF-Guideline-for-Type-2-Diabetes.pdf. Cited on 24 June, 2015.
4. Kalra S, Gupta Y. Insulin initiation: bringing objectivity to choice. Journal of Diabetes and Metabolic Disorders 2015; 14-17.
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|Publication:||Journal of Pakistan Medical Association|
|Date:||Feb 29, 2016|
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