May 28, 2010 | 7:13 pm

Carotid Artery Stenting Almost Ready for Prime Time

Posted by Albert Fuchs, M.D.

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Three months ago I wrote about carotid artery narrowing, which is one of a number of causes of stroke.  There are currently two alternative treatments for severe carotid artery narrowing:  surgery, called endarterectomy, to open the artery, and a newer procedure called carotid artery stenting.  (Read my previous post, link below, for some background about these procedures and their role in stroke prevention.)

Thus far, carotid artery stenting has not been shown to be as safe as endarterectomy.  So endarterectomy has remained the proven standard.

This week stenting finally gains some credibility in the largest study to compare the two treatments, published in this week’s New England Journal of Medicine.  Over 2,500 patients with carotid artery narrowing were randomized to stenting or endarterectomy.  They were followed for serious complications immediately after the procedure or for strokes in the subsequent years.

Surprisingly, the patients receiving stenting did overall as well as the patients undergoing endarterectomy, making this the first study in which endarterectomy was not clearly superior.  Stenting carried a slightly higher risk of stroke after the procedure, but endarterectomy had a higher risk of heart attack.  Interestingly, patients younger than 70 tended to do better with surgery, while older patients did better with stenting.

So stenting is finally finding some role in treating carotid artery narrowing.  Training and experience in the physician performing either procedure is vital.

An editorial in the same issue of the New England Journal of Medicine concludes

… until more data are available, carotid endarterectomy remains the preferred treatment for most patients with symptomatic carotid stenosis; treatment for asymptomatic stenosis remains controversial. However, given the lack of significant difference in the rate of long-term outcomes, the individualization of treatment choices is appropriate.

Learn more:

New England Journal of Medicine article:  Stenting versus Endarterectomy for Treatment of Carotid-Artery Stenosis

New England Journal of Medicine editorial:  Carotid-Artery Stenting in Stroke Prevention

LA Times Booster Shots:  Angioplasty plus stents is as good as surgery for clearing neck arteries, study finds

My previous post about carotid artery stenting:  Carotid Stenting Still Controversial

Important legal mumbo jumbo:
Anything you read on the web should be used to supplement, not replace, your doctor’s advice.  Anything that I write is no exception.  I’m a doctor, but I’m not your doctor despite the fact that you read or comment on my posts.  Leaving a comment on a post is a wonderful way to enter into a discussion with other readers, but I will not respond to comments (just because of time constraints).

May 21, 2010 | 5:41 pm

A Brief History of Unnatural Selection

Posted by Albert Fuchs, M.D.

Indulge me as I digress from writing about health this week to write about an important scientific breakthrough.

People have been altering the living things around us as long as we have been around.  We domesticated wild wolves into tame dogs and kept them for protection and as pets.  Eventually humans began to farm, and raise livestock.  We then began selecting the best animals to breed for the next generation, and we selected seeds from the best plants to sow.  Generation after generation, we changed the animals and plants that we had domesticated by allowing only those with characteristics we valued to reproduce.  We had no idea what made wheat grain larger or why some sheep grew more wool, we just knew that these traits are inherited, and by breeding the right specimens we could get more of what we wanted.  Through this simple repetitive selective breeding all human crops and domesticated livestock eventually became unrecognizable from their wild origins.  The wheat we eat today has about as much resemblance to pre-human wheat as my neighbor’s yippy dachshund has to a wolf.

So millennia before any people were rigorously studying living things (engaged in what we now call biology) people were progressively modifying many animal and plant species.  In 1859 Charles Darwin published “On the Origin of Species” his landmark work which argued that just as people select the pet cats and tomatoes and carrots that form the next generation, nature selects the survivors of every species to reproduce.  He proposed that it is this selection by nature (i.e. natural selection) that explains how all species change over time and how new species arise from older forms.

At about the same time Gregor Mendel showed that inheritance follows certain predictable patterns.  The offspring are not simply a blend of the traits of the parents.  Rather the parents’ traits are somehow transmitted in distinct indivisible packages (now called genes) which are inherited and expressed according to simple rules he described.

In the 1940s and 50s the molecule carrying genetic information was found to be deoxyribonucleic acid, DNA.  And in 1953 James Watson and Francis Crick discovered the shape of the DNA molecule – the double spiral staircase – that allowed it to serve as a molecular information storehouse.

Since then the fields of molecular biology and genetic engineering have exploded, with the development of techniques to identify, isolate and sequence genes.  In 1977 the entire set of genes (genome) of a virus was sequenced, meaning its entire DNA code was deduced.  Since then the genomes of many species, including humans, have been sequenced.  Genes have been inserted into crops to make them more resistant to disease and the molecular mechanisms of some genetic diseases have been discovered.

(By the way, those who object to genetically modified organisms in their food should not eat any crops at all since all modern crops have been modified through human selection since prehistory.  Genetic modification is just a finer tool for continuing the work of millennia.  Now that I think about it, these critics should also only keep wild tigers and wolves for pets.)

This week another threshold has been crossed.  Investigators synthesized an entire genome from scratch, inserted it into cells that had their original DNA removed, and formed cells that reproduced and expressed their new synthetic genes.  The effort took 15 years.  The achievement has no immediate practical uses.  It was simply a demonstration of the technologies required for such a feat.  Potential practical uses are myriad, but are likely far off in the future.  Their discovery was published in the journal Science and has received much press attention.

Though we have much more to learn, the pace of discovery is accelerating.

Learn more:

Wall Street Journal article:  Scientists Create Synthetic Organism

Science article:  Creation of a Bacterial Cell Controlled by a Chemically Synthesized Genome

The Ancestor’s Tale by Richard Dawkins is a fascinating tour through the history of life on Earth.

Important legal mumbo jumbo:
Anything you read on the web should be used to supplement, not replace, your doctor’s advice.  Anything that I write is no exception.  I’m a doctor, but I’m not your doctor despite the fact that you read or comment on my posts.  Leaving a comment on a post is a wonderful way to enter into a discussion with other readers, but I will not respond to comments (just because of time constraints).

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May 14, 2010 | 4:49 pm

Maybe You Have Food Allergies, But Probably Not

Posted by Albert Fuchs, M.D.

A lot of people who believe they have food allergies don’t.  What’s worse, a lot of people who were told by their doctor they have food allergies don’t.

An article in the current issue of the Journal of the American Medical Association tried to review the existing literature on food allergies to standardize how food allergies are diagnosed.  What the study found was an inconsistent jumble of unreliable test results and methods.

First, to clear up some of the confusion, we have to understand the difference between food allergy and food intolerance. A food allergy is a reproducible adverse reaction to a specific food that is mediated by a specific antibody that your body makes.  It usually results in a rash or difficulty breathing and can be life-threatening.  The article estimates that more than 1% or 2% of the population (but less than 10%) have true food allergies.

Food intolerance is any other adverse effect from food.  Lactose intolerance, for example, is the inability to digest lactose, the carbohydrate in dairy products.  It leads to abdominal discomfort and diarrhea whenever dairy foods are ingested.  It is not an allergy.  Neither is acid reflux, which can be exacerbated by certain foods, or gustatory rhinitis, in which spicy foods cause a runny nose.  These are all food intolerances.  So if you get heartburn every time you eat mint, you’re not allergic.  You just have acid reflux that is exacerbated by mint.

But we doctors are a more important source of the confusion.  Unfortunately, there is no easy way to accurately test for food allergies.  The most common tests are skin prick tests, in which small amounts of the food proteins are injected into the skin, and blood tests which look for antibodies to certain food proteins.  The problem with both tests is that they are very inaccurate and yield many false positives – the tests can be abnormal even when the person is not allergic.  So based on these tests many patients have been incorrectly told that they have a food allergy.

The most accurate way to diagnose a food allergy is a food challenge – a patient is given the test food in a disguised form so that she doesn’t know if it is the suspected allergen or a placebo.  Then the patient is observed.  This is accurate but impractical.  The patient must be under observation for a prolonged time in a facility that is equipped to handle a potentially life-threatening allergic reaction.

So the current state of the field is disorganized.  There is no standardized accepted way to accurately test for food allergies, and without that foundation, no way to study them.  The authors conclude

“There is voluminous literature related to food allergy, but high-quality studies are few. Prime needs for advancement of the field are uniformity in the criteria for what constitutes a food allergy and a set of evidence-based guidelines on which to make this diagnosis.”

Learn more:

Los Angeles Times Booster Shots:  With food allergies, much is said but little is known, conclude researchers

New York Times article:  Doubt Is Cast on Many Reports of Food Allergies

Journal of the American Medical Association article:  Diagnosing and Managing Common Food Allergies

Tangential miscellany:

An article in the current issue of Annals of Internal Medicine reviews the experience of the Israeli Field Hospital that responded to the Haiti earthquake. The field hospital had 121 medical staff and 109 support personnel. They arrived 89 hours after the earthquake with a mobile hospital that had operating rooms, intensive care units, equipment for radiology and laboratory testing, and medications. In 10 days they triaged 1,111 patients, hospitalized 737 of them and performed 244 surgeries – an impressive demonstration of logistical, medical and humanitarian preparedness.

Annals of Internal Medicine article:  Early Disaster Response in Haiti: The Israeli Field Hospital Experience

Important legal mumbo jumbo:
Anything you read on the web should be used to supplement, not replace, your doctor’s advice.  Anything that I write is no exception.  I’m a doctor, but I’m not your doctor despite the fact that you read or comment on my posts.  Leaving a comment on a post is a wonderful way to enter into a discussion with other readers, but I will not respond to comments (just because of time constraints).

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May 7, 2010 | 5:55 pm

Zostavax is Safe, Effective, and Not Free

Posted by Albert Fuchs, M.D.

Varicella zoster virus (VZV) is the virus that causes chicken pox, usually a relatively minor childhood illness.  Unlike other viruses that are cleared from our bodies after infection, VZV stays in our sensory nerve cells forever.  Over the subsequent decades our immunity to VZV wanes.  When our immunity falls too low, VZV can reactivate and cause shingles.  Shingles is a painful blistering rash along the distribution of one sensory nerve.  The rash resolves in a few weeks, but in some older patients the effected patch of skin can remain painful for months or even permanently.  This painful condition after shingles is called postherpetic neuralgia and it can be quite debilitating.

In 2006 a vaccine to prevent shingles, Zostavax, became available.  It is recommended for everyone over 60 who has had chicken pox.  It has been proven effective in preventing shingles, and therefore in preventing postherpetic neuralgia.

But is Zostavax safe?  A large study in the current issue of Annals of Internal Medicine answered that question.  The study randomized over 38,000 patients to receive Zostavax or a placebo injection.  The side effects from Zostavax were not worse than from placebo.  Most of the side effects (like most vaccines) involved inflammation at the site of injection.

So to summarize, Zostavax is safe, and it effectively prevents a very painful potentially disabling condition. Recall also that all children are now being vaccinated against chicken pox, so that in 60 years Zostavax will not even be necessary since a generation will have grown up uninfected with VZV.

In anything resembling a rational healthcare delivery system champagne corks would fly, the makers of Zostavax would get a pat on the back (and well-deserved profits) and we would all shift our attention to more pressing matters.  Some patients would decide to buy Zostavax; some would not.  Private or government charity programs would pay for the vaccine for indigent patients.  Joy and health would reign.

But instead, there is gnashing of teeth and wringing of hands.  Why?  Because only about 7% of eligible patients have received the vaccine.  It turns out Zostavax is the most expensive vaccine recommended for adults (about $200) and the first to be covered by Medicare part D, the Medicare drug “benefit”.  That means pharmacists are paid to dispense it to patients, not doctors.

To sort out why more patients aren’t receiving Zostavax, another study in the same issue of Annals of Internal Medicine surveyed hundreds of primary care doctors about the barriers that might be preventing them from recommending and administering Zostavax to their patients.  The results: the biggest barrier was financial.  Many patients without coverage don’t want to pay for it, and doctors aren’t being paid by insurance companies to administer it.

This was such a staggeringly shocking finding, that it merited an editorial in the very same issue of Annals.  That’s three articles about a vaccine that works as intended and is safe.  The editorial opines that reimbursement should be revised to promote increased utilization of the vaccine.  In other words, we should take more money from other people to assure that patients who don’t want to pay for their own Zostavax can get it for free.

Now don’t get me wrong, I’m all for charity care for indigent patients.  (I volunteer at a clinic that serves indigent patients two afternoons a month.)  But the vast majority of patients who aren’t getting Zostavax aren’t poor; they just have better things to do with $200.

What the editorial didn’t say is that you can’t do much better than a product or service in which the main barrier to obtaining more is the price.  After all, that’s the only reason we don’t get twice as many clothes or cars or homes.  If the price was lower, we would.  If Zostavax was free, some other barrier to its use would necessarily arise, perhaps a lengthy wait, or a difficult to navigate bureaucracy, or rationing by some other means.

So perhaps each patient should shoulder the cost of his or her own Zostavax.  We should also all donate a little time or money for those who truly can’t afford it.  And some of us may rationally choose to accept the risk of shingles.  Alternatively, we could riot in Athens until the EU pays to keep us all shingles-free.

Learn more:

Annals of Internal Medicine Summary for Patients:  Safety of the Vaccine to Prevent Shingles

Annals of Internal Medicine article:  Safety of Herpes Zoster Vaccine in the Shingles Prevention Study

Annals of Internal Medicine article:  Barriers to the Use of Herpes Zoster Vaccine

Annals of Internal Medicine editorial:  The Looming Rash of Herpes Zoster and the Challenge of Adult Immunization

Important legal mumbo jumbo:
Anything you read on the web should be used to supplement, not replace, your doctor’s advice.  Anything that I write is no exception.  I’m a doctor, but I’m not your doctor despite the fact that you read or comment on my posts.  Leaving a comment on a post is a wonderful way to enter into a discussion with other readers, but I will not respond to comments (just because of time constraints).

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