Medicine laboratory - over-fasting skews blood-lipid results?

Author

over-fasting skews blood-lipid results?

alanh_27@yahoo.com

2005-03-29, 7:18 pm

does excess fasting before a blood-lipids test, artificially push down
the reported lipid levels?

Jason

2005-03-29, 7:18 pm

In article <1111461659.435654.101740@g14g2000cwa.googlegroups.com>,
alanh_27@yahoo.com wrote:

> does excess fasting before a blood-lipids test, artificially push down
> the reported lipid levels?

It could have an effect. My doctor told me to fast only 12 hours prior to
my last blood lipid test. The reason behind it is to clear out any
medications or other substances in your bloodstream that might cause the
test to reveal incorrect results. For example, if you took a chol. pill or
blood pressure pill one hour before the test--the results would be vastly
different than if you had taken the pills 12 hours before the blood test.
If you fasted for 24 hours or more prior to the blood test--that could
also effect the final results.

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Robert

2005-03-29, 7:18 pm

"Jason" <jason@nospam.com> wrote in message
news:jason-2203051019320001@pm2-broad-178.snlo.dialup.fix.net...
> In article <1111461659.435654.101740@g14g2000cwa.googlegroups.com>,
> alanh_27@yahoo.com wrote:
>
>
> It could have an effect. My doctor told me to fast only 12 hours prior to
> my last blood lipid test. The reason behind it is to clear out any
> medications or other substances in your bloodstream that might cause the
> test to reveal incorrect results. For example, if you took a chol. pill or
> blood pressure pill one hour before the test--the results would be vastly
> different than if you had taken the pills 12 hours before the blood test.
> If you fasted for 24 hours or more prior to the blood test--that could
> also effect the final results.
>
> --
> NEWSGROUP SUBSCRIBERS MOTTO
> We respect those subscribers that ask for advice or provide advice.
> We do NOT respect the subscribers that enjoy criticizing people.

I would seriously doubt that. I have never heard of that before. There are
medications that impact thyroid function and glucose metabolism which effect
lipid levels but the fasting pertains to triglycerides in relation to food
which cause the greatest fluctuations. The eleveated triglycerides causes
interference with the other lipid measurements.
There are newer tests out there in which the LDL is directly measured and
therefore fasting is not needed at all.

>
>
>

Robert

2005-03-29, 7:18 pm

"Jason" <jason@nospam.com> wrote in message news:jason-> Robert,
> I was not aware of the newer LDL tests. I'll let my doctor know about
> them--she still wants me to fast 12 hours prior to my blood tests. She
> told me that if I did not fast for 12 hours that it would have an effect
> on the results.
> If you are involved in the medical profession--I'm sure that you know more
> about this subject than I know. I
> Jason

It is method specific as to whether one has to fast or not. Most places
still perform calculated LDL's and those that do must fast and they usually
ask you if you have been fasting or not before they draw the blood.
We will switch over to directly measured LDL's after we get our Architect
instrument up and running and will eliminate the data entry or ask patients
whether they are fasting or not.
Most doctors are aware of the clinical situations in which a direct LDL is
needed rather than the calculated one.

>
> --
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>
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JEDilworth

2005-04-05, 6:13 pm

Seems to me I barely remember, from my chemistry lectures 30 years ago,
that there are two types of triglycerides: exogenous and endogenous. You
must fast 12 hours to get rid of the exogenous portion (those derived
from your immediately recent food intake) so that testing only measures
endogenous triglycerides (those derived from your body metabolism). The
fasting has nothing to do with clearing medications. Obviously a
nonfasting accurate test would be nice. Again, not every lab has changed
over to new methodology.

Correct me if I'm wrong, chemistry folk.

Judy Dilworth, M.T. (ASCP)
Microbiology

Robert

2005-04-05, 6:13 pm

"JEDilworth" <bactitech@nospamhortonsbay.com> wrote in message
news:15idnd5qxsnp3NnfRVn-oQ@buckeye-express.com...
> Seems to me I barely remember, from my chemistry lectures 30 years ago,
> that there are two types of triglycerides: exogenous and endogenous. You
> must fast 12 hours to get rid of the exogenous portion (those derived
> from your immediately recent food intake) so that testing only measures
> endogenous triglycerides (those derived from your body metabolism). The
> fasting has nothing to do with clearing medications. Obviously a
> nonfasting accurate test would be nice. Again, not every lab has changed
> over to new methodology.
>
> Correct me if I'm wrong, chemistry folk.
>
> Judy Dilworth, M.T. (ASCP)
> Microbiology
>

Clin Ther. 2003 May;25(5):1490-7. Related Articles, Links

The relationship between nonfasting and fasting lipid measurements in
patients with or without type 2 diabetes mellitus receiving treatment with
3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors.

Weiss R, Harder M, Rowe J.

Androscoggin Cardiology Associates, Auburn, ME 14210, USA,
rweiss@exploremaine.com

BACKGROUND: Studies have confirmed a lack of patient and physician adherence
to the revised National Cholesterol education Program (NCEP) Adult Treatment
Panel III (ATP III) guidelines. These guidelines state that lipid panels
should be obtained while the patient is in the fasting state. However, this
restriction may limit the ordering of these tests and thus decrease the
number of patients on drug therapy and the number treated until goal
cholesterol levels are reached. Evidence shows that testing in the
nonfasting state may not be clinically or significantly different from
testing in the fasting state in identifying patients at risk for a future
cardiovascular event. OBJECTIVES: The purpose of this study was to determine
whether a relationship exists between nonfasting and fasting lipid values in
diabetic or nondiabetic patients that will permit the more ready
identification of patients who require treatment to meet NCEP ATP III
guidelines. A secondary goal was to determine whether diabetic patients who
appear to have reached goal cholesterol levels in the fasting state meet
those goals when the non-high-density lipoprotein cholesterol (HDL-C) levels
are measured in the nonfasting state. METHODS: This observational study was
conducted at Androscoggin Cardiology Associates (Auburn, Maine). Patients
with hyperlipidemia receiving statin therapy whose doses had not changed for
> or =2 months were enrolled. For all patients, nonfasting and fasting lipid
panels (total cholesterol, triglycerides [TGs], and HDL-C) were calculated,
whereas low-density lipoprotein cholesterol (LDL-C)levels were measured
directly. The direct LDL-C method was used to determine the variance of the
calculated LDL-C from the actual value. RESULTS: One hundred consecutive
hyperlipidemic patients were tested. Patients included 70 men and 30 women,
with a mean (SD) age of 66.2 (12.0) years(range, 24-93 years). Eighteen
patients had type 2 diabetes mellitus (DM). Non-fasting TG, HDL-C, and LDL-C
levels were able to identify almost all patients who did not meet ATP III
guidelines in terms of cholesterol levels (95%, 100%, and 95%,
respectively). No predictive differences were found, regardless of whether
the patients had type 2 DM. For the total population, statistically
significant differences were found between calculated nonfasting and fasting
measurements for mean (SD)LDL-C levels (90.2 [24.8] mg/dL vs 99.7 [26.1]
mg/dL, respectively; P < 0.001).The regression equation was fasting LDL-C =
22.7 + 0.854 x nonfasting LDL-C.A nonfasting LDL-C level >130 mg/dL
predicted a fasting LDL-C level >100 mg/dL(95% CI, -12.79 to -6.24), and a
nonfasting LDL-C level >130 mg/dL predicted cases of fasting LDL-C level
>100 mg/dL (95% CI, -5.79 to -1.35). CONCLUSIONS: In this study population,
nonfasting TG, HDL-C, and LDL-C levels successfully identified almost all
patients who did not meet ATP III guidelines for cholesterol levels. No
clinically significant difference was found in diabetic or nondiabetic
patients.

PMID: 12867223 [PubMed - indexed for MEDLINE]

Circulation. 2004 Nov 2;110(18):2824-30. Epub 2004 Oct 18. Related Articles,
Links

Multivariate assessment of lipid parameters as predictors of coronary heart
disease among postmenopausal women: potential implications for clinical
guidelines.

Shai I, Rimm EB, Hankinson SE, Curhan G, Manson JE, Rifai N, Stampfer MJ, Ma
J.

Department of Nutrition, Harvard School of Public Health, Boston, MA 02115,
USA. ishai@hsph.harvard.edu

BACKGROUND: Over the past decade, lipid measurements have been significantly
improved and standardized. We evaluated the usefulness of multiple plasma
lipid parameters in predicting coronary heart diseases (CHD) among women.
METHODS AND RESULTS: Among 32,826 women from the Nurses' Health Study who
provided blood samples at baseline, 234 CHD events were documented during 8
years of follow-up. In a nested study, these cases were matched to controls
(1:2) for age, smoking, fasting status, and month of blood draw. We
estimated the relative risk (RR) for each lipid parameter, adjusted for
C-reactive protein, homocysteine, body mass index, family history,
hypertension, diabetes, postmenopausal hormone use, physical activity,
alcohol intake, and blood draw parameters. The RRs associated with an
increase of approximately 1 SD (mg/dL) were as follows: HDL cholesterol
(HDL-C) (RR=0.6 [0.5 to 0.8], SD=17), apolipoprotein B100 (apoB100) (RR=1.7
[1.4 to 2.1], SD=32), LDL cholesterol (LDL-C) (RR=1.4 [1.1 to 1.7], SD=36),
total cholesterol (TC) (RR=1.4 [1.1 to 1.6], SD=40), and triglycerides
(RR=1.3 [1.0 to 1.5], SD=80). Among the lipid indexes, the RRs were:
apoB100/HDL-C (RR=1.7 [1.4 to 2.1], SD=1.0), TC/HDL-C (RR=1.6 [1.3 to 1.9],
SD=1.3), LDL-C/HDL-C (RR=1.5 [1.3 to 1.9], SD=1.0), and non-HDL-C (RR=1.6
[1.3 to 1.9], SD=42 mg/dL). After simultaneous control for several lipid
biomarkers, HDL-C was the primary contributor of the variation in
multivariate models (P=0.01), followed by LDL-C (P=0.01), whereas
triglycerides and apoB100 did not contribute further information.
HDL-C-related ratios were the strongest contributors to predicting CHD
(P<0.0001). CONCLUSIONS: Lower levels of HDL-C may be a key discriminator of
higher CHD events among postmenopausal women. HDL-C-related ratios (such as
TC/HDL-C) provide a powerful predictive tool independently of other known
CHD risk factors.

PMID: 15492318 [PubMed - in process]

Clin Chim Acta. 2003 Nov;337(1-2):49-57. Related Articles, Links

Normal ranges of non-fasting triglycerides in healthy Dutch males and
females.

van Wijk JP, van Oostrom AJ, Castro Cabezas M.

Department of Vascular Medicine G02.405, university Medical Center, PO Box
85500, 3508 GA, Utrecht, The Netherlands. j.p.h.vanwijk@azu.nl

BACKGROUND: Increased triglycerides (TG) are associated with
atherosclerosis. We determined free-living non-fasting TG concentrations in
healthy Dutch subjects. METHODS: Capillary TG (TGc) was self-measured by 109
males and 104 females during 3 days, on six fixed time-points each day;
fasting, before and 3 h after lunch, before and 3 h after dinner and at
bedtime. Daylong TGc-profiles were calculated as area under the mean
TGc-curve (TGc-AUC). Reference values for "high" and "normal" daylong TGc
concentrations were calculated as the 95th and 75th percentiles,
respectively. RESULTS: Fasting TGc were higher in males compared with
females (1.41+/-0.75 versus 1.27+/-0.59 mmol/l), resulting in higher TGc-AUC
(25.4+/-10.4 versus 20.6+/-9.8 mmol h/l). The highest TGc-concentrations
were found in the evening. The majority of subjects (95%) had TGc during the
evening below 4.6 mmol/l in males and below 3.7 mmol/l in females.
Seventy-five percent of the subjects had TGc during the evening below 2.9
mmol/l in males and below 2.2 mmol/l in females. During the day (with
exclusion of post-dinner TGc), 95% of the subjects had TGc below 3.7 mmol/l
in males and below 3.6 mmol/l in females. Finally, 75% of the subjects had
TGc during the day below 2.5 mmol/l in males and 1.7 mmol/l in females.
CONCLUSIONS: The present data may help to delineate normal ranges of
non-fasting TG and could be used to detect groups at risk for
atherosclerosis on the basis of a disturbed TG metabolism.

PMID: 14568180 [PubMed - indexed for MEDLINE]

Jason

2005-04-05, 6:13 pm

In article <15idnd5qxsnp3NnfRVn-oQ@buckeye-express.com>, "JEDilworth"
<bactitech@nospamhortonsbay.com> wrote:

> Seems to me I barely remember, from my chemistry lectures 30 years ago,
> that there are two types of triglycerides: exogenous and endogenous. You
> must fast 12 hours to get rid of the exogenous portion (those derived
> from your immediately recent food intake) so that testing only measures
> endogenous triglycerides (those derived from your body metabolism). The
> fasting has nothing to do with clearing medications. Obviously a
> nonfasting accurate test would be nice. Again, not every lab has changed
> over to new methodology.
>
> Correct me if I'm wrong, chemistry folk.
>
> Judy Dilworth, M.T. (ASCP)
> Microbiology

Judy,
I believe that you are 100 percent accurate in what you wrote. My doctor
told me to fast 12 hours and explained the reasons. My memory is not
perfect but I seem to recall that she told me almost the same thing that
you stated. I made the mistake of believing that another purpose of the 12
hour fast was to clear out the medication but I could have been wrong
about that issue.
Jason

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