Disclaimer: The following guide is my best guess on what content will be on the exam. I do not know what exactly will be on the exam but I have helped over a thousand health care professionals pass the exam.
Chapter 3- Definition, Classification and Diagnosis of Diabetes
Importance: High- Re-read a few times, be familiar with chapter
Approximate time recommended: 45 min
I have highlighted what I think will be important for the exam. All areas in grey (key messages and recommendations) are also important for the exam. However you should read the entire chapter.
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Open in new tab Under the heading of: Definition of Diabetes and Prediabetes
Remember that diabetes is defined as
1) defective insulin secretion (slowly declining ß-cell function with type 2 diabetes or quick autoimmune destruction of ß-cells with type 1 diabetes)
2) defective insulin action (most commonly insulin resistance due to obesity but could also be from pregnancy or a number of other factors)
3) a combination of both. Please see my pathophysiology lectures for more details
Anyone has has impaired fasting glucose AND/OR impaired glucose tolerance AND/OR an A1c between 6.0% – 6.4% has pre-diabetes, whether they have all of the above factors or just one of the above factors.
Under the heading of: Classification of Diabetes
Type 1, type 2, and gestational diabetes are the types of diabetes most likely to be tested on the exam.
LADA Diabetes
Think of Latent Autoimmune Diabetes in Adults (LADA) as type 1 diabetes that appears later in life. I have a 62 year old patient who has had LADA for about 10 years now. 10 years ago, the endocrinologist thought it was type 2 diabetes at first but with subsequent lab work she found the patient was GAD positive but still had c-peptide levels (0.64 nmol/L- normal is 0.30-2.40 nmol/L per Alberta Health Services) and diagnosed her with LADA diabetes. At first she was just on metformin. The plan was to monitor her c-peptide levels every 6 months and if they dropped then we would change her to MDI (multiple daily injections) insulin. Her A1c has trended upwards and slowly we added Jardiance (empagliflozin, which is not on label but the endocrinologist prescribed it not me). Then we added Ozempic (semaglutide) a few years ago. Her A1c slowly rose so we added Tresiba (degludec) 8 units and last year we added Trurapi (aspart) 2-4 units with her supper. She still has positive c-peptide levels (0.26 nmol/L so lower than the reference range but not zero) so despite it being 10 years since she was diagnosed, her ß cells are still producing her own insulin (though much less). Typically the later in life the type 1 diabetes is diagnosed, the slower the process of ß cell destruction.
MODY Diabetes
Monogenic diabetes is rare (1-2% of diabetes) form of diabetes that results from a genetic defect that leads to impaired ß cell development, impaired ß cell glucose sensing, or defects in the ATP K+ channels in ß cells. The impairment depends on the gene affected and there are a wide variety of gene defects but all of these are classified as monogenic diabetes.
Do memorize Table 1 and Table 2. It is important on the exam (and in real practice) to be able to distinguish type 1 diabetes from type 1 diabetes.
Under the heading of: Diagnostic Criteria
Memorize Table 3 and be familiar with Table 4
A repeat confirmatory test for diabetes should be done to remove the possibility of lab errors and other issues. Unless the person is showing symptomatic hyperglycemia or metabolic de-compensation (extreme thirst, frequent urination, weight loss, etc.) then the person should be treated right away as their symptoms confirm their diagnosis. This is particularly important with people who may have type 1 diabetes as they may go into diabetic ketoacidosis if left untreated.
Under the heading of: Prediabetes
Memorize Table 5
Under the heading of: Metabolic Syndrome
Be familiar with Table 6
The below video is a nice simple summary of the different type of diabetes. For further details please see the pathophysiology lectures.
Practice Questions (press show answer to reveal answer)
Which of the following patients has diabetes, pre-diabetes or no diabetes (assume confirmatory tests have been done and show the same result)?
Patient A- 40 year old male with a FBG of 6.1 mmol/L, a 2 hrPG in a 75g OGTT of 7.8 mmol/L and an A1c of 6.0% (0.06)
Patient B- A 18 year old female with a FBG of 7.1 mmol/L, a 2 hrPG in a 75g OGTT of 6.9 mmol/L and an A1c of 5.9% (0.059)
Patient C- A 80 year old female with a FBG of 6.0 mmol/L, a 2 hrPG in a 75g OGTT of 7.7 mmol/L and an A1c of 5.9% (0.059)
Patient D- A 60 year old male who complains about rapid weight less and frequent urination who had a random glucose of 11.1 mmol/L
A) This patient has pre-diabetes. Whether he has IFG and/or IGT and/or an A1c of 6-6.4% means he has pre-diabetes
B) This patient has diabetes as she has a FBG over 7.1 mmol/L. Having only one parameter in the diabetes range means diabetes regardless of the other parameters
C) This patient has no diabetes.
D) Because this patient has symptomatic hyperglycemia that is diagnostic of diabetes
Your 65 year old male patient has the following parameters: an A1c of 7.6%, high c-peptide levels, negative islet antibodies, is overweight and has a multi-generational family history of diabetes. What type of diabetes does he likely have?
A) Type 1 diabetes
B) Type 2 diabetes
C) Gestational diabetes
D) Monogenic diabetes
A) Incorrect- this is very unlikely because the patient is older, he has high c-peptide levels and is negative for islet antibodies. It is possible that he has type 1 diabetes but the question asks what is most likely
B) Correct- this is by far the most likely. He is an older gentleman, has c-peptide meaning he still has endogenous insulin production, high levels of c-peptide which suggests high insulin resistance, negative islet antibodies which suggests that the immune system is not involved and is overweight which suggests insulin resistance
C) Incorrect- this patient is male and 65 so its unlikely to be pregnant
D) Incorrect- while its possible that this patient has monogenic diabetes its unlikely. Monogenic diabetes is rare relative to type 2 diabetes.
Material that is relevant to your practice but may not be on the exam below:
Under construction.
I am going to go into a deep dive into monogenic diabetes below. Sometimes the exam has questions on this and sometimes it doesn’t. However there seems to be more research into this area as the genetic sequencing to diagnose monogenic diabetes seems to be improving. This section is based on the three studies at the end.
MODY sometimes presents with characteristics that are similar to type 1 diabetes, then the patient gets diagnosed as type 1 diabetes, and then gets started on insulin. Correct diagnosis is important as depending on the particular gene affected, the patient can be treated with sulfonylureas or even just lifestyle changes. There have been advancements in genetic testing that results in a more accurate MODY diagnosis . However genetic testing is expensive and not readily available. Only people who have been assessed to be at high risk for MODY diabetes should have genetic testing. There is a calculator here that you can use to assess the risk of your patients- https://www.diabetesgenes.org/exeter-diabetes-app/ModyCalculator
MODY diabetes seems to fall into two or three major categories.
Neonatal diabetes is a category of MODY diabetes and is diagnosed before the age of 6 months. It often due to defects in the ZAC and HYMAI genes.
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