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May
2001
Ultrasound
Not an Accurate Screening Test for Down Syndrome
About
5,000 babies are born each year with Down syndrome, a condition
that causes varying degrees of mental disabilities and physical
abnormalities. Because of the difficulties associated with raising
a child with Down syndrome, some women choose to test for the
condition.
The most reliable prenatal test for Down syndrome is amniocentesis,
a process in which the clinician inserts a needle through the
woman's abdomen to remove and analyze a sample of amniotic
fluid. While the test is about 99% accurate, it increases the
risk of miscarriage anywhere from 0.5-1%.
Because of the risks associated with amniocentesis, some clinicians
have suggested that ultrasound should be used as a screening
test to determine whether certain markers exist that suggest
the baby may be born with Down's and that an amniocentesis
is warranted. Ultrasound is a painless, non-invasive, general
screening device that uses sound waves to view the fetus. It
is widely used during the second trimester of pregnancy as
a routine part of prenatal care.
While the idea of a non-invasive prenatal test is encouraging,
ultrasound is not an accurate method of screening for Down
syndrome, according to a study in the Journal of the American
Medical Association. The analysis of 56 studies published
between 1980 and 1999 found that only one of the markers found
on an ultrasound, a thickening at the back of the neck, was
reliable enough for a physician to recommend amniocentesis.
Other markers present on an ultrasound, such as brain cysts
and bright spots on the bowel, were often harmless and not
reliable indictors of Down syndrome. The researchers concluded
that the dangers associated with an amniocentesis based on
most ultrasound markers are greater than the possibility of
having a child born with Down's.
May
2001 Update
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National
Cholesterol Education Program Releases New Guidelines for Treating
and Preventing High Cholesterol
On May 15, 2001, the National Cholesterol Education Program (NCEP) — coordinated
by the National Heart, Lung, and Blood Institute (NHLBI) — released
the first major revision of its recommendations for detecting and
lowering high cholesterol in adults since 1993.
One of the fundamental features of the new guidelines is the
accurate assessment of heart disease risk using a new "global
risk assessment tool" that combines multiple risk factors
into a measure of a person's absolute risk of developing coronary
heart disease within the next 10 years. According to the guidelines,
patients who have a risk of 20% or higher should receive aggressive
therapy to control cholesterol levels. In addition to aggressive
treatment of high LDL cholesterol, as laid out in the 1993 report,
the revised guidelines also recommend a more assertive treatment
approach for diabetes, low HDL levels, and high triglyceride
levels.
Specific changes include:
- Treating
high cholesterol more aggressively for those with diabetes,
even if they do not have heart disease.
- A full lipid
profile (which measures total cholesterol, LDL, HDL, and triglycerides)
as the first test for high cholesterol (rather than simply
testing total cholesterol and HDL and performing a full lipid
profile only if total cholesterol is high).
- A
new level at which low HDL becomes a major risk factor for
heart disease. The 1993 guidelines defined a low HDL as less
than 35 mg/dL; now it is less than 40 mg/dL.
- More
aggressive treatment of high triglyceride levels.
- Advising
against the hormone replacement therapy (HRT) as an alternative
to cholesterol-lowering drugs for post-menopausal women.
Another
key change in the guidelines is intensified lifestyle recommendations
regarding nutrition, exercise, and weight control to treat high
cholesterol. The updated diet advises that less than 7% of daily
calories come from saturated fat and limits dietary cholesterol
to less than 200 mg per day. It also allows up to 35% of daily
calories from total fat, provided most come from unsaturated
or monounsaturated fat, which doesn't raise cholesterol levels.
Additionally, the guidelines strongly underscore the need for
weight control and physical activity, both of which improve various
heart disease risk factors.
The revised recommendations also emphasize careful attention to the metabolic
syndrome, a particular cluster of cardiovascular risk factors
that is becoming increasingly common in the United States. Characteristics
of metabolic syndrome include too much abdominal fat, high blood
pressure, high blood sugar, elevated triglycerides, and low HDL.
For more information, see the "Live Healthier, Live Longer"
Web site by going to the NHLBI home page at www.nhlbi.nih.gov and
clicking on ATP III Cholesterol Guidelines under Highlights.
2001
Cholesterol Guidelines |
| Total
Cholesterol Level |
Total
Cholesterol Category |
| Less
than 200 mg/dL |
Desirable |
| 200-239
mg/dL |
Borderline
High |
| 240
mg/dL and above |
High |
| LDL
Cholesterol Level |
LDL-Cholesterol
Category |
Less
than 100 mg/dL
|
Optimal |
| 100-129
mg/dL |
Near
optimal/above optimal |
| 130-159
mg/dL |
Borderline
high |
| 160-189
mg/dL |
High |
| 190
mg/dL and above |
Very
high |
Trigylceride
Level
|
Triglyceride
Category |
| Less
than 150 mg/dL |
Normal |
| 150-199
mg/dL |
Borderline
high |
| 200-499 |
High |
| Greater
than or equal to 500 |
Very
high |
| HDL
Cholesterol Level |
HDL-Cholesterol
Category |
| Less
than 40 mg/dL |
Low
(representing increased risk) |
| 60
mg/dL and above |
High
(heart protective) |
|
Three
Categories of Risk that Modify
LDL Cholesterol Goals |
Risk
Category |
LDL
Goal (mg/dL) |
| Coronary
Heart Disease (CHD) and CHD equivalents |
Less
than 100 |
| Multiple
(2+) risk factors |
Less
than 130 |
| 0-1
risk factor |
Less
than 160 |
|
| Risk
factors (exclusive of LDL cholesterol): cigarette smoking;
blood pressure greater than or equal to 140/90 mm Hg or
on antihypertensive medication; HDL cholesterol less than
40 mg/dL; a family history of coronary heart disease before
age 55 in a father or brother or age 65 in a mother or
sister; age above 45 for men and 55 for women |
May
2001 Update
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Study
Shows Fish Consumption Protects Against Stroke, But
FDA Suggests Pregnant Women Should Take Caution
A
large study in the Journal of the American Medical Association (JAMA)
recently showed that regularly eating fish might protect against
ischemic stroke, which is the most common type of stroke. Numerous
studies have already shown an association between fish consumption
and a reduced risk of heart disease. But there is a caveat. The
Food and Drug Administration (FDA) recently warned that pregnant
women and women who are of childbearing age who may become pregnant,
should avoid certain types of fish that contain high levels of
mercury, which may be harmful to their unborn children.
Results of the Nurses' Health Study, published in the JAMA article,
involved nearly 80,000 women. It showed that women who ate fish
two to four times a week had a 48% lower risk of ischemic stroke — the
kind caused by blood clots — than
women who ate fish less than once per month. Even women who ate
fish only once a week or less had a risk reduction, but it was
not statistically significant. These results held true primarily
among women who did not regularly take aspirin, which prevents
the formation of blood clots. Omega-3 fatty acids, the protective
substances found in fish, reduce levels of fats related to cardiovascular
disease and help prevent blood clotting. Dark, oily fish such
as mackerel, salmon, and sardines are a good source of omega-3
fatty acids.
Although pregnant women need not give up fish — and
its beneficial health effects — altogether,
they should be careful about what types of fish they eat. The
FDA has advised that pregnant women and those who may become
pregnant stop eating shark, swordfish, king mackerel, and tilefish.
These large, long-living fish contain hazardous levels of methyl
mercury, a form of mercury that can accumulate in a woman's
body and affect the developing central nervous system of an
unborn child. This can lead to babies with slower cognitive
development. As an extra precaution, the FDA advised that nursing
mothers and young children also avoid these fish. Mercury gets
into both fresh and salt water through industrial pollution.
Some critics feel the FDA's mercury warnings are not strong
enough. A report by the National Academy of Sciences suggested
the exposure limits for mercury should be four times stricter.
While this controversy remains unresolved, the FDA encouraged
pregnant women to continue to eat a variety of other fish,
containing very low levels of mercury, as part of a balanced
diet. Among other health benefits, the fatty acids in fish
enhance brain development. According to the FDA, women can
safely eat up to 12 ounces of fish per week. Fish that contain
low levels of mercury include shellfish, canned fish, smaller
ocean fish, and farm-raised fish. Women who eat fish caught
by family or friends should contact their local health department
for advice on the safety of fish from local waters.
May 2001 Update
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