MadSci Network: Medicine

Re: Is it okay to have high HDL (outside the normal lab range)?

Date: Sun May 29 11:35:23 2005
Posted By: Jens Peter Bork, M.D., Internal Medicine, Erlangen University Hospital
Area of science: Medicine
ID: 1114008553.Me


thank you very much for your question regarding high HDL cholesterol. It is
in some ways a sticky question, and a lot of work goes into solving it. 

First, the "normal values". In their simplest form, reference values
represent the range of values in which 95 % of the individuals of a study
population are found. If a reference value is constructed in this way , 5%
of all people will have "elevated" levels by definition. 

The difficult part is the selection of the study population. Is it
representative of the larger population? Are there systematic differences
between different groups in the general population ie have gender
differences been adequately addressed etc. 

In the case of cholesterol, reference values are no longer simply averages
+/- deviations in study populations. Take the US, for example: The
proportion of very heavy people with high and dangerous cholesterol levels
is high there - so if we take an "average" section of the population of the
US and measure their cholesterol values to construct a reference value from
these measurements, the "normal" range will be placed in a region that
might actually be dangerous. Therefore, the reference values as they are
currently given also include some concept about what "healthy" (as opposed
to "normal") cholesterol values should be. For example, the reference value
(taken from the Dept. of Clinical Chemistry  of a large German University
Hospital) for total cholesterol is given as 130 - 260 mg/dl; in a further
qualification, <200 mg/dl is given as "optimal", > 250 mg/dl is marked as
being "associated with elevated cardiovascular risk".  (LDL: < 150 mg/dl =
"ideal", 150 - 175 = "suspicious", >175 =  "elevated risk". HDL: >65 mg/dl
in men/ >55 in women = "standard risk", <45 (m)/ < 35 (f)= "elevated
risk"). The values in other countries, such as the US, should be similar. 

As you can see, a higher level of HDL cholesterol affords protection from
cardiovascular risk. So, yes, you can have a situation where total
cholesterol is on the "high" side but this elevation is caused solely by an
elevation in HDL - and in that situation, there is no elevated
cardiovascular risk, although the "raw" cholesterol data would suggest that
there was. This is the reason why an isolated cholesterol determination is
not recommended to identify people at elevated cardiovascular risk -
without information about the other fractions, it cannot guide clinical

To do justice to this situation, other "yardsticks" to assess
cardiovascular risk have been developed. On of them is the ratio between
total cholesterol and HDL - Depending on the situation (age, other
cardiovascular risk factors), values of <6.5 or <5 are recommended. 

Finally, activities to lower total and LDL cholesterol usually lead to
higher HDL levels, both in relative and in absolute terms.  So if I had to
choose between several "elevated" blood values - A high HDL would
definitely be my choice!

All the best
Jens Peter Bork

[1] http://circ.ahajo is a nice
nontechnical description of the role of HDL written for patients.
[2] http://jam
At this URL, you find the current guidelines on Detection, Evaluation and
Treatment of Elevated Cholesterol, published in 2001. Very technical and
demanding, even to a physician. The text (in the Journal of the American
Medical Association) is not free, so you would a library with an online
subscription. Alternatively, this free publication:
has a link to the free full text (although without figures and tables). The
guidelines are ref. no. 3, there is „Free Full Text“ link on which to
click. The article itself is also interesting, dealing with the question of
how family physicians can assess cardiovascular risk in an asymptomatic
patient from their office desk.

All articles are extensively referenced for further reading. 
If you want to countercheck what reference values for HDL, LDL, total
cholesterol etc. are currently used, a Google search will take care of that. 

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