Sunday, December 6, 2009

More What You'd Call "Guidelines" than Actual Rules



Of course, Captain Barbossa was referring to The Pirate Code, but he could just as easily have been referring to documents released last month by the US Preventive Services Task Force or the American Congress of Obstetricians and Gynecologists (ACOG).


In an unanticipated coincidence, these two groups, operating independently, reached similar conclusions about commonly utilized screening tests: mammograms and Pap smears. Both groups reviewed the data and concluded that routine use of these screening tests, as currently recommended, may not be warranted.



Much newsprint has been expended since then discussing the political implications of these new recommendations. As this is not a political blog, I will leave that discussion to others.

What I want to talk about is how guidelines (should) influence patient care.


I think a lot of the worry surrounding these guidelines stems from concerns that they will be interpreted by those who pay the bills in our system (meaning the Federal Government, through Medicare reimbursement regulations, and the private insurance industry) as “Actual Rules” rather than “Guidelines,” meaning that if you get a mammogram or a Pap smear but don’t meet the “Guidelines” your service won’t be covered. In the current environment, this may be true, but it shouldn’t be.

The key to my argument is the highlighted words above: “routine use” and “as currently recommended.”

The key to understanding why both groups reviewed the published data and reached similar conclusions is an understanding of the nature of screening tests as well as a bit on biostatistics. My work colleagues who read this will laugh at the idea that I am trying to teach anyone statistics, but that’s what I’m going to do.

To start, the accuracy and usefulness of any medical test can be described by the terms “sensitivity” and “specificity.” Sensitivity refers to how likely the test is to be positive if the condition is present. So a sensitive test will pick up every case. Specificity is the mirror image – if the test is positive, how likely is it that the condition is present. Screening tests are designed to be very sensitive, even if they are not very specific – that way, no cases are missed (very sensitive), but sometimes the test is positive even if the patient does not have the disease (not very specific).

The other statistical consideration is the concept of positive- and negative-predictive value. This means, how likely is a positive test to mean the disease is there, or how likely is a negative test to mean the disease is absent? Two concepts factor into the positive- and negative-predictive values of a test: the sensitivity and specificity AND how common the condition is in the population being tested.

These considerations underlie the new recommendations. Mammograms save lives. No one disputes that. Early detection of breast cancer saves lives. No one disputes that. But mammograms are not very specific, and the positive-predictive value of a positive mammogram is MUCH more if the woman is at risk of developing breast cancer than if the woman is at relatively low risk. Since a woman with a strong family history of breast or ovarian cancer is at higher risk of developing breast cancer in her 40’s than a woman with no such history. Thus, the positive-predictive value of a mammogram in a 40 year old woman is higher if the woman is at higher risk. This is why the Task Force no longer recommended ROUTINE mammograms for women under 50.


This is where the practice of medicine comes in. As the doctor treating a 40 year old woman, it is important to remember that a mammogram will be valuable if the woman is at risk, but far less valuable if the woman is NOT at high risk. So blindly refusing to order a mammogram simply because the patient is 40 makes no sense (and an insurance company refusing to pay for it based solely on age makes equally little sense). A 40 year old woman whose mother had breast cancer should have a mammogram and it should be covered. A 40 year old woman with no relatives who have ever had cancer may not need a mammogram. Determining whether a screening test is needed is a decision for the doctor and the patient to make together.



This isn’t rationing care, this is good medicine.


Related Posts:
As Breast Cancer Month Draws to a Close
Breast Cancer Risk & Alcohol
Is the Medical Community Complicit?

8 comments:

Anonymous said...

This is a tough issue for those of us who are in the "grey areas." My doctor referred me for a mammogram at age 32 because I had a large, benign-feeling lump. In the past I had a low grade bone sarcoma, and this scared her (she actually looked scared) because I had a "cancer history." So she sent me for a mammogram but told me she thought it was nothing. This frustrated me, but I figured she knew best.

Of course, the mammogram was not specific enough, and the next thing I knew I was being hauled in for a painful biopsy. Gynecologists evidently standardly recommend that you have a lumpectomy after you have a breast biopsy, even if the biopsy is clear! I don't know if that is because of cell damage or because scans in the future will be worrisome without having the lump removed. So even when the results were fine, my GYN recommended surgery to remove 5cm of fibrocystic tissue.

The long and short of it is, I avoided having unnecessary surgery by going to the best breast cancer surgeon in my city, who took one look at my tests, did a quick exam and told me I had nothing to worry about. If I had not referred myself to him, he told me the surgery would have definitely taken a good chunk of my body with obvious cosmetic damage for no good reason...basically because I had a "history" and was referred for a mammogram. It was not a fun ride.

jaime said...

I'm not sure how to comment on this post.....as someone who may be personally affected by both new "guidelines", I have strong feelings. I am also someone who routinely goes for biopsies and as much as I hate them, on a very basic, fundamental survival-instinct level, I would rather have my cervix scraped or tissue removed from my breast and find out I am fine, rather than go with a "likely normal" test result or assume I am "low-risk" and it's not warranted.
UNC radiologist Etta Pisano has posted a response on You Tube to the Task Force guidelines re:mammograms, and it's worth taking a look at.....

Doctor David said...

I knew this one would generate some controversy. What I had hoped would come across was 1) these are guidelines, not rules, and in the end the decision to get a screening test of any sort should come from a conversation between a doctor and her patient and 2) there is a downside to getting a screening test, so it makes sense to understand the risks and benefits.


Anonymous, you illustrated my points perfectly (thanks!). You had a conversation with your doctor, decided to have a test, and almost had an unnecessary surgery as a result of a "false positive," one of the risks inherent in any screening test. I'm glad you found a doctor who gave you good advice and you avoided a disfiguring surgery you didn't need.

Jaime, your preferences for biopsies rather than going with "likely normal" is just why these guidelines need to be guidelines and not rules. For every woman like you, there will be another one who would rather NOT have the biopsy. A regulatory agency shouldn't make that decision, the woman and her doctor should. However, ACOG and the Task Force should review the available literature objectively and report their results and issue guidelines so that the discussion you have with your doctor is informed by research. That's how women and men end up making the best possible decisions.

MarilynMann said...

Actually, specificity is the probability that a test will be negative among patients who do not have the disease.
Specificity = TN/(TN + FP)
Where TN = true negative
and FP = false positive

One thing many people fail to realize is that false positives resulting in unnecessary biopsies is not the only harm that can come from cancer screening. If cancer is picked up on a screening test and treating the cancer prolongs the person's life significantly, that is a benefit. But that is not always the case. In some cases, the cancer would never have progressed to a stage that would cause symptoms, in which case the treatment is all harm and no benefit. In other cases, the cancer is so aggressive that treating it does not make much different, with the result that the patient endures more years of being a cancer patient with little or no benefit.

One of the problems with mammography is that mammograms pick up many cancers at a very early stage, such as ductal carcinoma in situ (DCIS) and small invasive cancers. Some cases of DCIS, if left untreated, will progress to invasive cancer. Unfortunately, we have no way of knowing which ones, so all cases are treated, primarily with surgery and, in the case of breast-conserving surgery, radiation. Some of these women will also be treated with endocrine therapy. Unfortunately, all these treatments are pretty drastic and can affect quality of life. Many breast cancer survivors suffer from chronic pain as a result of being treated.

It is also suspected that some cases of invasive cancer never would have progressed to the point of causing symptoms. Again, there is currently no way of knowing which ones.

One thing that has been developed in recent years is gene expression tests, such as Oncotype DX, that give some women with early stage breast cancer a prediction of how likely they are to have a distant recurrence, which allows some of them to forgo chemotherapy.

So, yes, mammograms save lives, but they also cause harm. Each woman needs to weigh the benefits and risks based on her own values and situation.

Doctor David said...

Thanks, Marilyn. I was pretty sure I'd get the stats wrong if I was brave enough to put something up in public. Thanks, also, for expanding on the issues surrounding false positive screening tests. I completely agree that, in the end, each woman has to weigh the risks and benefits for herself and make the decision that is right for her.

Will FitzHugh said...

David, great explanation! The best way I've heard of explaining positive predictive value is that it's the fraction of positive test results that truly have the condition you're testing for.

So if the positive predictive value of a mammogram for women aged 40-49 is 4% (from http://www.ahrq.gov/clinic/3rduspstf/breastCancer/brcanrr.htm) then only 4% of women with a abnormal mammogram (I hesitate to call it a 'positive' result...) actually had a tumor.

So the point of the guidelines is that cost (financial/emotional/physical), for those 96% who got abnormal results but didn't have cancer, outweighs the benefit for the 4% that did.

Of course, and this is the point that critics of these 'guidelines' make, those 4% might have gone undiagnosed had they not had a mammogram. But as you point out, they would have if they'd had some other risk factor such as family history.

outre said...

I can almost hear the insurance companies rejoicing about the new guidelines.

Regarding the last sentence of your post, to a degree, healthcare is being rationed by the insurance industry. I'm not sure why people that are against a healthcare reform think the current state is 'whenever, wherever you want' when in reality that's not true. Maybe they are just using that as an argument or more likely, haven't experienced denials by the insurance companies beyond the 'no, we are not going to cover a brand name when a generic exits.'

Doctor David said...

Will, great summary. I couldn't have said it better myself.

Outre, at the risk of being political when I said my blog is not a political one... you're right. Health care is already rationed in this country. I guess the point I was trying to make, though, is that these guidelines are not an attempt to ration care, they are an attempt to provide guidance about when screening tests should be used. Guidance in the ordering of screening tests isn't rationing of care. At the same time, guidelines such as these should never supercede the medical decisions made by a doctor and a patient together. They can guide these discussions and decisions, but should be guidelines rather than actual rules.