Genetic Analysis: Guest Blogger Bethany Macmanus

Today, I'm pleased to host author and friend, Bethany Macmanus. She's guest blogging on what diseases can be discovered through genetic analysis.

Bethany has graciously agreed to award one e-book copy of Nerve to a commenter of this posts. Comments close on Wednesday, March 25th. 

Welcome, Bethany!

I've always found the ancient “nature vs. nurture” debate interesting, to the point of writing a paper on it for my Child Growth and Development class in college. What determines a person's physical traits, IQ, personality, or even their ability to process things like gluten and phenylalanine? Is it mostly their environment, or is it mostly their genes?

I've heard of individuals who live the most healthy life they think possible, by exercising regularly, eating what they've been told is most nutritious and balanced, and seeing their physician for recommended appointments. When they wake up one day and find out they have advanced cancer, they wonder what in the world happened. Their environment, though it couldn't be controlled completely, had been “nurtured” as much as possible. What, then, did their genes contribute to the equation?

The answer is, probably a lot.

Geneticists are discovering more and more factors which are predetermined by what is written on our DNA. Here is only a partial list, which I've taken from www.geneplanet.com:

·         Episodic memory (KIBRA gene)

·         Pain sensitivity (SCN9A gene)

·         Norovirus resistance (FUT2 gene)

·         Bitter taste perception (TAS2R32 gene)

You may have heard of the double mastectomy actress Angelina Jolie underwent in 2013 to prevent breast cancer. Genetic analysis showed she had a specific BRCA1 gene mutation, which is reported to make her 87% likely to test positive for the disease. The BRCA1 and 2 genes are responsible for tumor suppression.

I wondered what other disease processes can be tested through genetic analysis. Gene Planet has a long list: Alzheimer's disease, asthma, atrial fibrillation, breast cancer, celiac disease, colorectal cancer, gallstones, glaucoma, heart attack, hypertension, lung cancer, MS, prostate cancer, psoriasis, rheumatoid arthritis, diabetes (type 1 and type 2), restless leg syndrome, and venous thromboembolism (a blood clot in an extremity).

The list included a lot of the diseases with high mortality rates, which made me have another thought. If I had one or all of these (very expensive) analyses done, I sure wouldn't want this genetic information falling into the wrong hands!

And so I asked one of the story questions in my novel, Nerve: What if a sample of my DNA was stolen from me and analyzed without my knowledge or consent? What might the thief do with their new power over me? Find out when you read!

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Bethany Macmanus lives in Houston with her husband, daughter, and son. After practicing as an RN for five years, Bethany left the nursing field to pursue a writing passion the Lord planted in her heart when she was a child. Nancy Drew mysteries were her guilty pleasure during those early years, so she naturally gravitates her pen toward the things that go bump in the night, and most of her plots have a psychological spin. She’s allergic to cheese, Sulfa drugs, and people who stop in the middle of intersections while driving.

Up and Coming

Hello Redwood's Fans!

How has your week been? Mine? Let's just say I'm glad I got that novel done last week because this week has been busy-- saving lives and teaching other people how to save lives.

Spring is coming. Do you love springtime? For me, spring is my third favorite season (behind autumn and winter). I'm ready for the snow to melt and for some warmer weather but I'm a cave girl so the bright sun is not always high on my list. Oregon, I think I'd do well living in your rainy state.

For you this week! Two fantastic ladies and guest bloggers.

Tuesday: Friend and author Bethany Macmanus stops by to guest blog on some of the diseases that can show up on genetic testing and how it inspired her latest novel, Nerve. Bethany has been kind enough to offer one free e-book to a commentor on her March 17th post-- so be sure to stop by.

Thursday: Forensic expert Amryn Cross answers an author's question. How early can a pregnancy be detected on autopsy?

Have a GREAT week.

Jordyn

Acetaminophen Poisoning

Acetaminophen, commonly known as Tylenol, is one of the number one ingestion (accidental and intentional) calls to the Rocky Mountain Poison Control Center. One of the reasons behind this is that Colorado has one of the highest rates of prescription drug abuse and acetaminophen is a common co-ingredient of narcotics (Vicodin, Percocet and others.)

Using a possible overdose in a novel is a good way to increase conflict/tension. Acetaminophen ingestion, if caught early enough, is highly treatable with a mortality rate of <0.5% which is in large part to N-Acetylcystein (NAC).

Acetaminophen was first used in 1955. It's primary function is as a pain reliever and fever reducer. It peaks in 45 minutes and the half-life is 2-3 hours. I discussed the importance of half-life and ingestions here.

Acetaminophen is metabolized by the liver which also becomes the primary victim in overdose. If untreated, acetaminophen kills off liver cells over the period of a couple of days. This type of overdose is the #1 cause of liver failure in the US, UK and Europe-- again, largely as a result of prescription drug use/addiction.

What's considered a toxic dose? Greater than 150mg/kg for a child and 7.5 grams and over for an adult. Keep in mind, extra strength tablets are 500mg each so taking just fifteen of these places a person in the toxic category. For an acute overdose, the entire amount needs to be ingested in eight hours. A person can still become toxic from chronic ingestions but it does complicate their medical management a little.

We do use decontamination at times in poisonings but the treatment for acetaminophen ingestion is so good that it generally outweighs the benefit of decontamination which is discussed here.

What's most important in acetaminophen overdose is the four hour drug level (four hours after the time of ingestion.) Whether or not to give the antidote is based on this level. Now, in a massive overdose (let's say twice the toxic level) the medical team may be directed to decontaminate the patient because the patient can die from a massive overdose even though their liver may be fine. At the four hour mark if the drug level is less than 150-- the patient does not require NAC. If over 150-- they get the treatment.

NAC can be given two ways-- either IV or by mouth and should be started within eight hours of ingestion. The oral route is preferred because it goes to the liver in higher amounts. NAC works by enhancing a protein that breaks down acetaminophen in the liver when it's own mechanisms are overwhelmed by the amount of drug the patient has taken.

Even if a patient denies taking acetaminophen, we'll generally test for it under suspicious circumstances-- such as admitting to taking another drug or suicide attempt through other means. In 8.4% of cases, the patient will test positive and 2.2% of those require extensive treatment.

A negative acetaminophen level doesn't mean they didn't take an overdose so in a patient where there is concern for acetaminophen toxicity-- we would also draw liver enzymes. If those are elevated, the patient will get the antidote even if the acetaminophen level is negative.

Patients generally die from cerebral edema or overwhelming sepsis. Researchers are unsure why the cerebral edema develops. Sepsis occurs because the liver protects the body against bacteria and if the liver has died-- their protective mechanism fails.

What's interesting in acetaminophen overdose is there is little intermediate ground. Either the patient gets better or they don't. Past a certain point, the only way to save them is to transplant their liver.

General Treatment of Ingested Drugs

One thing that has evolved a lot in medicine is the general treatment of drug overdoses. 

Early in my nursing career, I worked in a community ER. In this setting we saw both adult and pediatric patients. One day, three young boys were brought in after they'd gotten into grandma's medicine cabinet and sampled a multitude of pills. 

In those days, if the ingestion was within one hour, we did use Syrup of Ipecac to induce vomiting and each of these boys got a dose and a big bucket. Syrup of Ipecac is more effective the more water you drink. All three children were lined up next to one another, each on their own gurney, and I walked down the line encouraging each of them of drink. 

Soon enough, one of them began to vomit. One of the other boys proclaimed that wasn't going to happen to him and I simply gave him another glass of water to drink. After he saw his second sibling throw up, he said to me, "I don't want any more water." 

That didn't keep him from the invetible. 

What we learned is that causing patient's to throw up increased their risk of more serious complications-- like aspiration pneumonia. It is a risk that while vomiting, you'll inhale some of that material. 

Then there was "stomach pumping." There's a lot of confusion about what this actually is and the last time I did it was over twenty years ago. A large (literally garden size hose) is inserted down the patient's mouth into their stomach and then, through a pumping action, the stomach contents are washed out with large amounts of saline.

The problem with this therapy became the electrolyte shifts that can happen when replacing stomach contents with saline and this practice has been largely abandoned as well. Also, having a large tube put down into your stomach also increases your risk for vomiting and the same risk discussed above still applies.

What has remained is the use of activated charcoal. Activated charcoal literally looks like ground up charcoal. It is a thick, sludge like material that is sweetened to make is more palatable. In kids-- we usually put it in a covered up Styrofoam cup so they can't see it. If they won't initially drink it we may flavor it with chocolate milk. The problem becomes that whatever it is diluted in they have to drink all of in order to get the full dose.

Activated charcoal works by binding the drug to make it inactive. If the effects of the drug would be more detrimental to the patient (versus just observing and offering symptomatic support) then we'll generally try to give it if the patient comes in within one hour of the overdose.

With any ingestions, we usually follow the direction of our Poison Control Center.

If your child has ingested anything of concern, I highly recommend you call them first at 1-800-222-1222.