3

The meaning of “mean plasma glucose (MPG)” is unambiguous, but I’m having an incredibly difficult time making sense of the way the term “mean blood glucose (MBG)” is used in medical research literature on diabetes. It’s not clear whether it denotes mean plasma glucose as well, or whole blood glucose, or whether the term is used inconsistently in the literature.

I have seen several sources that assert that MBG is different from MPG and refers to whole blood glucose, and relate the two with the equation MPG = MBG * 1.11. However, none of the sources I’ve found that specifically distinguish between MBG and MPG are formal articles in medical journals.

In the professional literature, the term MBG is never clarified -- I haven’t been able to find even one paper that specifically defines it as either whole blood or plasma glucose -- and it seems to be used in inconsistent and contradictory ways between different articles. Some articles use the term MPG exclusively, and at no point distinguish it from MBG. Others use MBG exclusively, and neither distinguish it from MPG nor specify whether it refers to plasma or whole blood.

Still others alternate between the terms.

  • In some of those cases, context clearly implies that they have different meanings.
  • In other cases it’s unclear from context whether the terms are being used interchangeably (implying that MBG refers to plasma glucose), or whether two terms are used because they mean different things.
  • In still other cases, the term MBG is used in reference to the same things for which other articles use the term MPG, implying that the terms are interchangeable. For example, I’ve seen both the DCCT and ADAG conversion equations stated in terms of both MBG and MPG, but the numbers are always the same, and I’ve seen articles use the term MBG in reference to articles that only used the term MPG.
  • In no case, however, is it explicitly made clear whether and how MBG differs from MPG

I’ve provided examples of all of the above at the end, with links.

The ADAG study further adds to the confusion. The article never mentions either MBG or MPG, instead introducing the term “average glucose” (AG), without indicating whether it’s a synonym for MPG and/or MBG or whether there’s some distinction in meaning from either or both of those terms, nor whether it denotes whole blood or plasma glucose. I’ve gathered from numerous references to the ADAG study that AG is in fact plasma glucose, and that the ubiquitous regression equation produced by that study relates HbA1c to MPG (which further implies that articles that use MBG in the ADAG equation are treating it as synonymous with MPG). However, the article never actually specifies that the “average glucose” it talks about is plasma glucose, apparently assuming that this is self-evident to professionals, and sheds no light on the MBG/MPG distinction, if any, nor on why a different term is used in this article than in all other literature on the same subject. I haven’t seen the term AG used in any other article, except sometimes when citing the ADAG study.

I have had no luck in finding any information that clarifies how these terms are used. Can anyone shed some light on this so that I can be sure I understand the literature correctly?

  • Are MBG and MPG interchangeable, both referring to mean plasma glucose? If so, why do some articles use both, in a way that creates the impression that they have different meanings?
  • Does MBG mean something different? If so, what exactly does it mean, whole blood glucose, or something else? Why is the term sometimes used in articles discussing the relationship between blood glucose and HbA1c, given that research establishing that relationship (DCCT, ADAG, and the more recent GMI study) always quantifies it in terms of mean plasma glucose?
  • In either case, why does the ADAG study use a different term altogether? Is AG synonymous with MPG, or is there a distinction?
  • When the term MBG appears in articles, is it a safe assumption that any associated numbers are either plasma or plasma equivalent values?
  • In writing about this topic, is MBG the preferred (or at least acceptable) term to refer to averages based on values obtained by meters that report plasma equivalents and CGMs calibrated with such meters, or would that be considered ambiguous, and is the term MPG preferred?

Examples:

2
  • Adi, what is the context in which you need to know these exact terms: as a student, a doctor...?
    – Jan
    Nov 5 '19 at 17:08
  • @Jan As someone who is researching the relationship between A1C and glycemic control in diabetics and needs to make sure he's interpreting the medical literature correctly. My interest in this subject is highly practical as well as theoretical, but I'm not quite sure what bearing the specific nature of my interest has on the question, since it doesn't relate to individual circumstances. The meaning of the terminology may or may not be consistent across the literature, but I presume it doesn't vary according to any particular reader's source of interest...
    – Adi Inbar
    Nov 8 '19 at 4:35

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.