Cholesterol testing has traditionally required all patients to fast for eight hours prior to having their blood taken. However, a new look at the effect of fasting on test results and the reference ranges used to assess them show that fasting for many may be a thing of the past.
Cholesterol is part of the lipid profile tests that are used to assess a person’s cardiovascular risk and also to monitor patients who are being treated for an existing cardiovascular condition.
The tests include measurements of total cholesterol, HDL cholesterol and triglycerides. Patients are asked to fast before having the test because food in the system can affect results.
Test results are compared to a recommended range; this is the scale pathology labs use to report whether a lipid result is within a low or high cardiovascular risk range.
Contemporary thinking is that the effect of food on a person’s test result can simply be taken into account when evaluating the results of the initial test, as evidence shows that any difference in the test result because of the patient not fasting is usually small.
Should the lipid profile reveal something of concern, or if doctors feel a comparison is needed, the test can be repeated when the patient has fasted to give doctors information to compare.
This is good news for patients as fasting for eight hours can obviously be difficult and inconvenient. It is also welcome news for pathology collection centres that may have to turn away patients who are not aware of the fasting requirement and arrive for their test after a recent meal.
Chemical pathologist Dr Lee Price said: “Many patients aren’t told by their GP or referring doctor that they should fast, or they forget to, so are turned away when they go for the test.
Also fasting is often inconvenient. Many patients will choose to have the test first thing in the morning when collection centres are busiest, which is inconvenient for patients and staff.”
When asked if a patient could even present for a test straight after lunch, Dr Price cautioned that eating right before a blood test would still not be recommended. However, patients would only need to refrain from food for about two hours before the test, rather than eight.
Dr Price says that how test results are interpreted and how cardiovascular risk is assessed is now moving on; “We now want to know what levels are the majority of the time – as most people, most of the time are in a non-fasting state.”
There is still a place for fasting tests for comparison purposes and for assessment of those being treated for existing conditions, such as those who have had a heart attack or stroke who may be taking statin drugs.
With an ageing population and concerns about growing rates of obesity and chronic health problems, cardiovascular risk assessment is fairly common and is unlikely to decrease any time soon. This means many patients will benefit from the move to non-fasting tests and doctors will be able to more easily assess risk and take appropriate action.