Limits of normal


The neurologist I saw face to face.

We discussed a clinical case.

Involving depression

And a bad drinking session

And an interesting diagnostic chase.

Synopsis:  I’m a family practitioner from Sioux City, Iowa.  In May 2010, I left my position of 23 years, and honoring my non-compete clause, traveled for a year doing locum tenens work.  In June of 2011 I joined up with the Community Health Center, which provides care for the underserved.  I’m now working part-time, which, for a doctor, means 54 hours a week.

The lower limit of normal for Vitamin B12 has moved from 200 during my residency in the 80’s to a high of 287 in the mid ‘90s and has hovered at a more or less constant 220 ever since.  The lab report always comes with a  caveat: if the level is over 400, replacement rarely benefits the patient, but between 220 and 400, some people will benefit from B12 shots.

In the hospital parking lot a couple of decades ago, I stopped a neurologist for advice in generating an algorithm to deal with B12 deficiency.

In med school and residency, they taught us not to test anyone under 40, and not to test if the blood count (CBC) showed normal looking white cells without extra lobes in their nuclei, and normal, rather than large, red cells. 

By the time I’d been out of postgraduate training for ten years, I recognized I’d gotten a poor substitute for truth.  I’d tried pumping wisdom out of a hematologist (blood specialist) but quickly realized he didn’t know more than me. 

Then I spotted the neurologist in the parking lot while I puzzled over a patient, age 38, with numbness and a normal CBC but a B12 level less than 150.

Curbside consultation, the discussion of cases with colleagues on an informal basis, remains a vital institution even in the digital age, and comes with its own etiquette.

The neurologist smiled, and in less than 30 seconds slaughtered enough sacred cows for a Texas-sized barbecue.

Forget the CBC, concentrate on the symptoms.  In a patient over age 70 with symptoms and a level under 400, treat with injectable B12, don’t do any follow-up testing unless they deteriorate neurologically.  If you really, really want to know if B12 lies at the root of the problem, you can do further testing (methylmalonic acid and homocysteine levels) if you want, but at the rate of $3.50 per year of treatment, extra testing rarely justifies its cost.

Since then I learned that alcohol interferes with a body’s ability to utilize B12, thus most alcoholics have big red blood cells and levels of B12 over 3000.

B12 deficiency, formerly known as pernicious anemia because before B12’s discovery the patient always died, remains one of my favorite diagnoses.  I get to save the patient’s life for less than a penny a day, with an injection given once a month.

Yesterday on rounds I sat in a patient’s room and leafed through the lab work.  With very large red cells on the CBC, and some vague neurologic symptoms, I had ordered a B12 level two days before.  I suppressed a whoop of delight when I found a 188.  “We can help you,” I said.

One floor down, I talked with an alcoholic about a marginal B12 level, 244, and recommended starting B12 shots.  Your depression won’t improve, I said, if you don’t have enough B12, and it’s hard to control your drinking when you’re so depressed.

Then I walked, grinning, down the hallway.  My favorite diagnosis, twice in a morning.

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One Response to “Limits of normal”

  1. gold account Says:

    Yet it is well-established in the scientific literature that people with B12 levels between 200 pg/mL and 350 pg/mL – levels considered “normal” in the U.S. – have clear B12 deficiency symptoms . Experts who specialize in the diagnosis and treatment of B12 deficiency, like Sally Pacholok R.N. and Jeffery Stewart D.O. , suggest treating all patients that are symptomatic and have B12 levels less than 450 pg/mL. They also recommend treating patients with normal B12, but elevated urinary methylmalonic acid (MMA), homocysteine and/or holotranscobalamin (other markers of B12 deficiency).

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