Which Test is Needed? | QoW Rationale

Our September 15th Question of the Week quizzed test takers on figuring out which lab test was most needed based on the case history.

Before we start though, if you don’t want any spoilers and haven’t tried the question yet, you can answer below: Answer Question

Question: A 42-year-old woman arrives with an A1c of 10.3%, BMI of 32 and states she is ready to take better care of her type 1 diabetes. She uses a Freestyle Libre Sensor and takes 3-4 injections of insulin a day. Both her parents have type 2 diabetes and she says her diabetes was diagnosed after her third pregnancy. During this pregnancy, she had gestational diabetes and after delivery, her blood sugars never improved. Given this history, which of the following lab tests would clarify the best diabetes treatment plan?

Answer Choices:

  1. A1c and OGTT.
  2. Transglutaminase.
  3. TSH and T4.
  4. ICA, IAA, GAD.

As shown above, the most common choice was option 4, the second most common answer was option 2, then option 3, and finally option 1.

Getting to the Best Answer

If you are thinking about taking the certification exam, this practice test question will set you up for success. Test writers anticipate possible answers based on the details in the question. Many of the test questions are presented as clinical vignettes. Your job is to weed through the particulars, pluck out the most important elements and choose the BEST answer based on the evidence.

Answer 1 is incorrect. 11% of you chose this answer, “A1c and OGTT”. Based on her history, presentation, and A1c of 10.3%, she clearly has established diabetes. So there is no need to verify diagnosis by rechecking her A1c or administering an OGTT.

Answer 2 is incorrect. 9% of you chose this answer, “Transglutaminase”. This blood test is indicated to evaluate if someone has celiac disease. It is true that people with type 1 are at high risks for autoimmune conditions like celiac disease. However, we can only use the information contained in the case study to determine the best answer. Since she is not complaining of any GI issues or exhibiting any symptoms of celiac disease, this is not the best answer.

Answer 3 is incorrect. About 8% of you chose this, “TSH and T4”. These test are used to evaluate the health of the thyroid. It is true that people with type 1 are at high risks for autoimmune conditions like thyroid disease. However, we can only use the information contained in the case study to determine the best answer. Since she is not complaining of or exhibiting any symptoms of thyroid disease in this situation, this is not the best answer.

Finally, Answer 4 is correct. 72% chose this answer, ICA, IAA, GAD”. In chosing this correct answer, we consider her BMI of 32, plus the fact that both her parents have type 2 diabetes and she had gestational diabetes. Plus after delivery, her blood sugars never improved. We are wondering if she might actually have type 2 diabetes? Given her genetic history and weight, we are certainly observing that she is exhibiting signs insulin resistance, and might benefit from the addition of medications (GLP-1 RA, SGLT-2, metformin) approved for people with type 2 diabetes.

To verify that she has type 1 diabetes, we look at lab results to check if there is an autoimmune attack on her pancreas and insulin. If one or more of these tests come back positive, it indicates an autoimmune condition.

ICA – Islet Cell Autoantibodies
IAA – Insulin Autoantibodies
GAD – Glutamic Acid Decarboxylase

We hope you appreciate this week’s rationale! Thank you so much for taking the time to answer our Question of the Week and participate in this fun learning activity!


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