Fasting vs Nonfasting Lipid Values and Cardiovascular Risk: Q&A With Advisory Board Member, Eliot Brinton, MD
Nonfasting triglyceride values could potentially predict pancreatitis.
Eliot Brinton, MD, FAHA, FNLA is the president and director of the Utah Lipid Center and the Utah Atherosclerosis Society and Atherometabolism Institute, and advisory board member of The Cardiology Advisor.
Dr Brinton recently participated in a session in preventive cardiology at the 66th Annual Scientific Session & Expo of American College of Cardiology held from March 17-19, 2017, in Washington, DC. He discussed the value of fasting vs nonfasting lipid profile testing.
The Cardiology Advisor (TCA) attended the session and spoke with Dr Brinton after the meeting.
TCA: You mentioned that fasting triglyceride values can better predict risk of developing pancreatitis (especially >500 mg/dL). If this is the case, do they also better predict overall cardiovascular risk?
Dr Brinton: They do not necessarily predict better, but they predict different. We can get pretty good data from fasting triglyceride levels, but it is the nonfasting values that can predict pancreatitis. If a patient has an upward trajectory of nonfasting triglyceride values, they will probably develop pancreatitis. But, even with something that is clearly postprandial, fasting can still predict it. Triglycerides are variable to begin with, so if you start with nonfasting values, you just amplify the variability.
When you are treating patients with high cholesterol and their LDL (low-density lipoprotein) levels are less than 70, that is great, but you should still get their fasting triglyceride values because these patients have a high residual risk of cardiovascular events. Eating a standard (moderate- to low-fat) meal prior to triglyceride testing can cause the results to vary by up to 30%. That variation can be even higher (up to 50%) if the patient consumes a high-fat meal. So, why would you want to take the chance of dealing with such a wide variation?
For any clinician who is serious about lipids — either a board-certified or a board-eligible lipidologist — they should do virtually all their testing in fasting patients. Any other patient in whom lipid levels is a major part of follow-up should also undergo fasting tests.
TCA: Are fasting triglyceride levels also better predictive of increased cardiovascular risk in patients with metabolic syndrome or diabetes?
Dr Brinton: There is value in obtaining fasting levels in both conditions. In fact, the whole problem with metabolic syndrome is that it is defined by fasting triglycerides. If I am following a patient who may be developing diabetes, I need to see what their fasting values are. In a patient with prediabetes or someone who may have metabolic syndrome, I am way better off getting fasting triglyceride levels.
However, the other part of the story is that if I am following a patient for possible diabetes, fasting glucose tests are nearly always better. The ADA [American Diabetes Association] now allows us to use A1c levels, a nonfasting test, for the diagnosis of diabetes. But A1c values alone can be misleading. It is better to get a fasting glucose level and verify it in someone who may be prediabetic. This is critical in a patient who is at risk for diabetes, and in the United States, that is roughly one-third of the population.
TCA: Can you comment on the strong inverse relationship between triglycerides and HDL-C [high-density lipoprotein] levels in patients?
Dr Brinton: That is not directly related to the issue of fasting vs nonfasting levels. HDL-C is barely affected by fasting, so as a general rule it is okay to use the nonfasting value.
TCA: Do you generally order serum fasting lipids in all of your patients or do you try to use a more precision (case-by-case) medicine approach?
Dr Brinton: It is common practice in American medicine to perform tests on the day you see a patient rather than ahead of time. That is a routine, but perhaps should be changed in some cases. Ordering the tests and planning the visit in advance makes the whole practice 10 times better. As soon as lipid levels become an issue in a patient, having the test results in hand makes a world of difference in how the clinician and patient work together.
If you have to be the one to test the patient, and it is inconvenient for them to come to your office, I would point out that you follow that procedure at a price. You are seeing the patient without the lab work in hand. If the labs come back to you later, then you have to consider the results — what does the patient need to hear about them from me — but you cannot explain to the patient why their triglycerides got worse or better. You do not get to follow-up on any other issues. The big question is, do you want to have a critical part of your communication with your patient occur in those subpar circumstances?
I am not against nonfasting lipid profiles, although we used to think nonfasting values were worthless. But what I want to do is use this as an opportunity to have doctors reconsider how they see and treat patients with lipid disorders. There are advantages and disadvantages to both kinds of testing, but there are situations in which fasting is simply better.
For example, are you willing to diagnose a patient with metabolic syndrome without 2 out of 5 criteria, when 2 of the criteria are fasting values? If more than half of your patients either have or may have metabolic syndrome, you should also be obtaining fasting triglyceride levels to follow that condition. And, even if you are only treating a patient for high cholesterol, you should be periodically screening them for residual cardiovascular risk as well because taking statins predisposes people to diabetes.
Taking that concept a step further, when I put a patient who is prediabetic on a statin, I am obligated to double my efforts to try to prevent the development of diabetes.
A large percentage of people taking statins need both fasting triglyceride and fasting glucose tests. It is not that nonfasting profiles have no value, but do not throw the baby out with the bath water, if that makes sense.
Logistical factors can make obtaining fasting lipid profiles more difficult, but in the end, it is worth it for the patient and can be better for your practice.
TCA: Can you clarify your comment regarding the problem of patients being on insulin and/or sulfonylureas prior to obtaining a fasting lipid profile?
Dr Brinton: That was in regard to how risky it is for patients who already have diabetes to fast. Yes, it is an important issue, especially in patients taking either drug. However, only about 1% of patients with diabetes really ought to be on sulfonylureas — only a small percentage of the population.
Insulin is a different story. There are plenty of people who need insulin or they will die. I do not object to insulin per se, but for every 3 patients on insulin, there is probably 1 who ought to be off insulin. We should work to get those patients off insulin. The insulins of today are as expensive as any other diabetes drugs.
In my personal opinion, we are overusing short-acting insulin. It is difficult to predict the rate of absorption of glucose in these patients. The body is better at determining when you need insulin. If there is any way to deal with diabetes naturally, you should do everything in your power to enable that process.
So, yes, fasting is risky in this population because of hypoglycemia. But if you get these patients off these drugs, the risk decreases.
TCA: Can you provide further comment on the value of intermittent/periodic fasting on the risk of coronary atherosclerosis? Do you have any advice on how to discuss this topic with patients?
Dr Brinton: There is a potential value to periodic fasting. I thought I would mention the concept in the session as it is an interesting thought, and there is some nutritional research in this area.
The idea that it is intrinsically harmful to ask anyone to fast for 8 hours overnight is just not true. We should probably not be “grazing” as much as we do. Does fasting a few times a year have any real effect on a person's cardiovascular health? Maybe. But it could be beneficial in another way, even in patients with diabetes.
Brinton, Eliot. Fasting vs nonfasting lipid testing — not so fast, we still need to fast. Session 678: Great Debates in Preventive Cardiology. Presented at: the 66th Annual Scientific Session & Expo of the American College of Cardiology. March 17-19, 2017; Washington, DC.