Tuesday 8 January 2013

Fasting for cholesterol test - is it necessary?


       Image source: Thirteen Of Clubs - cc
                                                                       

Most of us would either have done a fasting cholesterol test, or heard about it.

Traditionally fasting was thought to be crucial for accurate cholesterol test results, but just how much difference does fasting improve the test result?


Having to fast for cholesterol test can be rather inconvenient. If you went to see a doctor for a check up and he (or she) decided to do some screening blood test including checking the cholesterol, you may be asked to come back again after you have fasted. This may be annoying as you have to make another trip, and sometimes battle for car park space (again!). For those of us who have a busy job this can be quite difficult, and for some people the inconvenience of this may result in not returning to the appointment and lost to follow up - until years later when heart attack or stroke ensue.

For people who do return to the follow up appointment, some of them may forget to fast in the morning while rushing to make the appointment - resulting in another reschedule. The others who do manage to remember to fast and attend the appointment, it is still uncomfortable having to sit in the doctor's surgery with a growling stomach.


Well, the good news is - all these problems may potentially become a thing of the past, according to the research by D. Sidhu and C. Naughler (published in Archives of Internal Medicine, 10 December 2012).

Sidhu and Naughler conducted a large community based cross-sectional cohort study involving 209180 participants (98132 males, 111048 females) in Canada in 2011. They designed the study to look at the differences in level of the cholesterols for fasting intervals of 1 hour to > 16 hours. The cholesterols they studied include:
    • Total cholesterol (TC)
    • High-density lipoprotein cholesterol (HDL) - aka "Good" cholesterol
    • Low-density lipoprotein cholesterol (LDL) - aka "Bad" cholesterol
    • Triglycerides (TG)
This study showed that fasting had minimal effect on total cholesterol and high-density lipoprotein cholesterol. With low-density lipoprotein and triglycerides, fasting compared to non-fasting had a variation in level up to 10% and 20% respectively. So essentially fasting only really matters for triglyceride, and to some extent the low-density lipoprotein .

How does these small variations affect you?

To put things in perspective, let's look at what the recommended level for cholesterol is. According to the ATP 3 (Adult Treatment Panel) guideline, the primary target for treatment is the bad cholesterol LDL, which should be less than: 100mg/dl (2.6mmol/l), 130mg/dl (3.4mmol/l), or 160mg/dl (4.1mmol/l), depending on how many cardiovascular risk factors a person has. So if you have no risk factors (hence target LDL <160mg/dl or 4.1mmol/l), and your NON-fasting LDL is 135mg/dl (3.5mmol/l), then you are well below the target range, even accounting for the 10% variation, and therefore a fasting test is not required.

In summary: for most people, fasting for cholesterol test is unnecessary unless the result is on the borderline of the recommended level. If that's the case, then a fasting cholesterol test may be considered if the doctor decides it would influence medical decision.




Summary of the Study




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