When you go to the doctor for a lab test or X-ray, you expect it to be accurate. Right?

You know mistakes can happen but, putting that aside for the moment, you expect that when a test shows things are normal, they are.

Well guess what? That’s not always the case, as you’ll see from my story below.

First, an example: A woman walks into her doctor’s office for an annual physical. The doctor listens to her heart, takes her blood pressure, discusses her cholesterol results, reads the EKG as normal and says, “You’re just fine. See you in a year.”

Then the woman walks out to her car and before you can say “boo,” she drops dead. (An aside here: Women are 10 times more likely to die prematurely from heart attacks and strokes than they are from breast cancer.)

So who’s responsible for this? Most of the time, it’s not the doctor but the assumptions by the doctor and the patient that normal tests mean you’re OK. Both doctor and patient rely on technology for picking up a problem when, in fact, technology has fatal flaws.

So on to my story about a patient of mine who moved to another city. She’s someone who lives an extraordinary lifestyle – exercises regularly, eats a heart-healthy diet, gets pap tests following the new recommendation to do this every three years for most women, and has mammograms.

Last January, her mammogram was read as normal. Three months later she noticed a breast lump when she was showering. She said to herself, “My mammogram was normal. I’m scheduled for another one in two years. This is probably just nothing.”

By the time she had finished her shower, however, she’d changed her mind and decided to see her doctor right away.

Long story short, as my son, Zak, would say, she has breast cancer. Luckily, it was caught early and she has a good surgeon and a good oncologist. But unluckily, her mammogram didn’t pick up the cancer.

She wondered, as would you or I, whether it was there but missed by the radiologist. But second opinions from two renowned radiologists showed it hadn’t been missed – it simply wasn’t there.

That’s when she called me. “Why did this happen?” she asked.

I explained that every test has a “missed” rate, something called a false negative. That’s where the test says the patient is OK when, in fact, the patient is not.

When she asked what that false negative rate was for mammograms, I told her I thought it was 5 percent. But after checking the National Cancer Institute website, I was floored to discover it’s a shocking 20 percent.

That’s right: One out of five women with breast cancer have normal mammograms.

Hearing that, she went to the bottom line. “Why wasn’t I told that when they called me and told me the mammogram was read as normal?” Good question, isn’t it?

My spin: Tests are only so good. Doctors are only so good. The best medical care is a combination of both technology and clinical judgment. And the secret ingredient in this sauce is you.

If you get a report but don’t think it’s right, don’t be lulled into complacency. Take action. If my former patient had simply relied on the test she might be dead. Stay well.

Dr. Zorba Paster is a family physician, university professor, author and broadcast journalist. He also hosts a popular radio call-in program at 3 p.m. Saturdays on WNED.