Tag Archives: screening

Prenatal screening for birth defects

Birth professionals who have been in the field a long time are well acquainted with the diagnostic tests for Down syndrome and other conditions (amniocentesis and CVS) and the challenges of explaining to clients: “Before you have the test, think about what you’ll do if you have a positive result.” Over the past 15 – 20 years, there’s been huge improvements in screening tests for these conditions, and those need to come with their own patient education and precautions about how to respond to a “screen positive” result.

Vocabulary: Before we talk about the tests, let’s talk about some terms:

  • Screening test – assesses how likely it is that baby has the condition being tested for.
  • Diagnostic test – determines whether the baby actually has the condition.
  • False negative is the chance that a test will come up negative when the baby actually DOES have the condition being tested for. This is obviously distressing for parents if they had tests done and were told the baby was fine, and then discover at birth that it’s not as they expected. A test with a detection rate of 90% would catch 90% of the cases, and have a false negative rate of 10%.
  • False positive is the chance that a test will come up positive when the baby does NOT have the condition. This could lead someone to take actions or have procedures that are not necessary. (See below.)
  • Screening threshold or “cut-off” – the answer to a screening test is not really Positive or Negative / Yes or No. It’s really “If we say you’re screen positive, that means you exceed the threshold at which we think it’s a good idea for you to have diagnostic testing to determine for sure whether or not you have that condition. If we say you’re screen negative, that means we don’t think it’s worth having more testing because we don’t think it’s likely you have the problem.” For example, if a test showed you had less than 1 in 50 chance of a problem, then it doesn’t make to have a test that has a 1 in 20 chance of creating a problem.
  • It is helpful to learn from a caregiver not just the screen positive or screen negative answer, but also what are your chances. For example, they might say you’re screen positive for something if the cut-off was that your risk was greater than 1 in 200. But, if your risk is estimated at 1 in 190, the recommended diagnostic test is not that likely to show you have the condition (though it’s probably still a good idea to have it.) If your risk is estimated at 1 in 10, not only will they recommend that diagnostic test, but it’s pretty likely it will turn up positive.
  • Aneuplody. Chromosomal abnormalities, such as trisomy 21 – Down Syndrome and trisomy 18 – Edward syndrome.

Should anyone skip screening tests and go straight to diagnostic tests?

In the past, often the recommendation for amniocentesis was made solely on the basis of the mother’s age (typically, for those over 35). The risk of aneuplodies goes up with age, so caregivers recommended the test when her risk of having a baby with a chromosomal condition was greater than the risk of miscarriage caused by amniocentesis. (At that time 1 in 200 risk.) Age is no longer considered reason enough for diagnostic testing. Most caregivers recommend that first a pregnant person have a non-invasive screening test,and only do a diagnostic test if her risk is higher than the screening threshold.

Some women are considered high enough risk that they could go straight to the diagnostic testing. typically that’s: if the baby was conceived by IVF, if the woman or her partner has a history of a previous pregnancy with a chromosomal abnormality, or if both partners are carriers of a genetic condition that increases the risk of chromosomal birth defects.

What screening tests are available?

(Note: WordPress tables aren’t always easy to read, so here’s a PDF of the tables if you prefer to view that… )

Test Type of test When done What is test screening for? Detection rate and false positive rate for Down syndrome (DS) and neural tube defects (NFD) Turnaround time from testing to results
First trimester blood test Blood test 10 – 13 weeks, ideally at 10 Tests levels for PAPP-A and HcG. Down syndrome, trisomy 13 and 18 Blood test: 69% with a 5% FPR (SOGC)

 

Days
Nuchal translucency screening

(may also assess for presence or absence of nasal bone)

Ultrasound 11 – 14 weeks, ideally at 11 Measures the thickness of a clear space at the back of a fetus’ neck. Babies with chromosomal disorders, such as Down syndrome, accumulate more fluid in this area Ultrasound:

69 – 75%. FPR 5 – 8% (SOGC)

 

When combined with first trimester blood test:

82 – 87% (ACOG) 83%, 5% FPR (SOGC)

Immediate to days
Cell-free fetal DNA testing (e.g. MaterniT 21). Also known as non-invasive prenatal screening (NIPS). Blood test 10 – 13 weeks, ACOG recommends that it be done only if blood test or nuchal translucency showed high risk (there’s a discussion of this here…) Tests for placental DNA in mother’s blood. Screening for Down syndrome, other trisomies, and fetal sex aneuploidies. Also reveals gender and baby’s Rh factor. 99% / FPR 0.2% (Source) 7 – 10 days
Second trimester blood test (quad screen) Blood test 16 – 20 weeks ideally at 16 – 17 Tests levels of alpha-fetoprotein (AFP), estriol, human chorionic gonadostropin (hCG) and inhibin A. Screen for Down and Edwards, plus neural tube defects. 81% (ACOG)

75-80%, FPR 3 – 5% (SOGC)

 

For neural tube defects: 71 – 90% with 1- 3% FPR (SOGC)

7 – 10 days
Second trimester ultrasound Ultrasound scan 18 – 22 weeks Screen for neural tube defects and other anatomical defects For NTD: 68 to 86% for neural tube defects (SOGC2) Immediate to days

Often test results are combined to increase accuracy. Here are some of the common combinations.

Type Combines results from Detection rate and FPR for Down syndrome When are results reported to parents
Integrated screening First trimester blood test, nuchal translucency ultrasound, and second trimester quad screen 94 – 96% (ACOG)

85 – 87% with FPR of 0.8% to 1.5% (SOGC)

92% with 3% FPR (Quest)

Results not reported until after the second trimester results are in
Serum integrated screening First trimester blood test and second trimester quad screen 85 – 88% (ACOG)

88, with 6% FPR (Quest)

Same as above
Sequential integrated screening First trimester blood test and nuchal translucency scan are done.

Then second trimester screening or diagnostic testing, depending on risk level.

95% (ACOG)

92%, with 4% FPR (Quest)

After first trimester tests, if risk is high, diagnostic testing is recommended. Otherwise, second trimester screening is done before results are reported
Stepwise sequential First trimester blood test and nuchal translucency scan.

Then no further testing, second trimester screening, or diagnostic testing, depending on risk level.

95% (ACOG)

92%, with 4% FPR (Quest)

After first trimester tests, results are reported. If high risk, diagnostic testing is recommended. If moderate risk, second trimester screening is recommended as a follow-up. If low risk, no further testing.

Explaining Test Results to Clients

It’s very important for expectant parents to understand the difference between a screening test and a diagnostic test, and important to understand what false positives are.

If a screening test comes up positive, one of the first questions an expectant parent should ask their caregiver is: how certain are we that this test is correct? Are there other tests I could have to confirm this?

They can ask their caregiver to explain the false positive rate – the chance that although they screened positive, the baby does not actually have that defect.There’s two sides to that… 1) what’s the false positive rate for all people tested and 2) amongst people who test positive, what percent of those are false positives and what percent actually have the condition. (This latter number is called the positive predictive value of a test.)

For example, all the advertising for cell-free fetal DNA testing will talk about how it will detect 99% of cases, and has a false positive rate of 0.2%. This is true, and MUCH more accurate than other screening methods. But it’s still not perfect. One study showed that of 1909 patients screened, most people screened negative. 11 screened positive. After diagnostic testing, it turned out that 5 of the 11 babies had Down syndrome and 6 did not. So, for the whole population screened, only 0.3% were false positives. But of those who screened positive, 55% of those were false positives. (Source)

In another study of cell-free fetal DNA testing, of 41 patients who screened positive, 38 were true positives. 3 were false- positives. (Source) Better… but still 7% of the people who screened positive were not.

A parent who has heard the 99% accuracy advertising may not be aware of the subtleties of all this, and may not fully understand what a screen-positive result means.

The rates of false positives with other testing are much higher than that, and even more important for expectant parents to understand in order to interpret what a “screen positive” result means. (Note: screening results should not just be given as “positive” or “negative.” They should also be given in terms of probability. For example,  “you have a 1 in 150 chance of this condition.” The expectant parents can ask for this information if it was not given to them clearly.)

Responses to a False Positive Test

In the case of Down syndrome, some parents might use a positive screening test result as a reason to spend the rest of their pregnancy learning about Down syndrome and lining up resources to help them care for their child. If they found out at birth that the test was a false positive and the baby did not have Down syndrome, it is likely they would be relieved not to need to use those resources.

However, a majority of expectant parents choose to terminate a pregnancy if the baby is diagnosed with Down syndrome.

The Society for Maternal-Fetal Medicine states

all positive cell free DNA screening results require confirmatory diagnosis before an irreversible action, such as pregnancy termination, is undertaken.   (Source)

However, 6 – 17% of those who screen positive with cell-free fetal DNA testing are choosing to terminate the pregnancy based on those results alone without any further testing.

Before getting testing, and definitely before getting results, it is very helpful for expectant parents to understand that a screening test is not absolute, and what their options will be. If they screen positive, they could choose diagnostic testing to confirm the diagnosis – CVS can be done at week 10 – 12, in time for a first trimester termination decision. If for some reason, CVS is not an option for the parents, another option could be additional screening tests. The cell-free fetal DNA testing, first trimester blood tests, and nuchal translucency look at separate factors, and having results from more than one test could be illuminating information to have before making an irreversible decision.

Learn more

An interesting article on this topic is Oversold and Misunderstood.

Or click on any of the links above…

Breast Cancer Screening Guidelines

If you just want a brief summary of guidelines, look here. For all the details, read on!

Breast Cancer Screening

Over recent years, there have been significant changes in recommendations for how to screen for breast cancer, how often, what age to start at, and what age to stop screening. A significant influence on the debate has been the recommendations issued by the United States Preventive Services Task Force (USPSTF) in 2009, which are summarized in the chart below. (Read the full document here. Our Bodies Ourselves has a helpful detailed examination of them here.)

Here is a review of current thoughts.

Methods of screening:

  • Breast self-exam (BSE) – Looking in the mirror for changes, then using a standardized pattern to methodically check the breast for lumps or other changes. (Instructions here.) Past recommendations were for monthly BSE, but research hasn’t shown much benefit to this routine, so it is no longer specifically recommended. Instead, they recommend breast self-awareness – this simply means being familiar with your breasts, and having a sense of what is normal for you so you can tell if there are any changes.
  • Clinical breast exam (CBE) – A health care professional examines your breasts, first looking at them for any abnormalities in size or shape, then using hands to feel the breasts, checking for lumps. CDC says it does not reduce the risk of dying from breast cancer
  • Mammograms – An x-ray of the breast. See details here. 70% of women over 40 have mammograms. (NY Times, 2013) It is the most effective method for finding breast cancer (though it has limitations as discussed below) and is recommended for all women, although recommendations range on frequency and on age to begin screening (See below)
  • Magnetic Resonance Imaging (MRI) – magnets and radio waves create detailed, cross-sectional image of the breast. Details here. It is recommended only for high risk women, and only in conjunction with mammograms. (See below.)

Incidence of Breast Cancer

About 230,000 women are diagnosed with breast cancer each year in the United States. That’s 14% of all cancer diagnoses. The chance that a woman will have breast cancer at some point in her life is around 12%, or 1 in 8 chance. Approximately 90% of breast cancer patients survive at least 5 years beyond diagnosis. (SEER)

The risk of breast increases with age. For a 30 year old, the chance she’ll have it in the next ten years is just .44% (1 in 227). For a 70 year old, the chance is 3.82% (1 in 26.) (National Cancer Institute)

Benefits of breast cancer screening:

Breast self-awareness and CBE may detect some tumors. Mammograms can find malignant tumors that could not be detected by hand. Screening can help to detect breast cancers when they are small and more treatable, and before they spread to other parts of the body. A small tumor is easier to remove and less likely to result in mastectomy. Dr. Richard C. Wender, chief of cancer control for the American Cancer Society says mammography reduces the death rate by at least 15% for women in their 40s and at least 20% for older women.

Another way of viewing this is: For an individual woman in her 40s, the chance of dying of breast cancer in the next ten years is .35% if she doesn’t have annual mammograms and .3% if she does. For a woman in her 50s, annual mammograms lower her risk from .53% to .46%. (NY Times, 2013)

For some women, regular screenings can also reduce their anxiety about developing breast cancer. Everywhere women go, they see pink ribbons, and messages that build their fear of breast cancer and reassure them that “mammograms save lives.” So, the annual checkup soothes their fears. (Interestingly, women may be overly fearful of breast cancer. The actual risk of having breast cancer in your lifetime is 12 – 13%. 89% of women overestimate that, with an average estimate of 46%. Science Daily.)

Hazards of breast cancer screening:

  • False negatives: Mammograms may miss 20% of tumors (National Cancer Institute). False negatives are more common for younger women, because mammograms are less effective on younger women’s breasts, which have denser tissue. Digital mammograms may be more effective for women under 50.
  • False positives: the mammogram may find something that after further testing turns out to not be cancer. False positives are more common for younger women, women with a family history of breast cancer, and women who are taking estrogen.
  • Additional testing and procedures: 10% of mammograms lead to follow-up testing. 8 – 10% of those women will get biopsies. (org) “Research has shown that as many as 75% of post-mammogram biopsy results turn out to be benign (non-cancerous) lesions.” (OBOS) In addition to the risks and costs of these biopsies, they put a huge emotional strain on the women involved as they go through a great deal of fear and anxiety through the testing, biopsy, and waiting for results.
  • Over-diagnosis / Over-treatment: Screenings may find DCIS (ductal carcinoma in situ – a non-invasive tumor, which can evolve into cancer) or slow-growing cancers that would never have caused symptoms or threatened the woman’s life. If these are treated, then the woman may be unnecessarily exposed to the side effects of cancer treatment.
    • A recent Canadian study found 22% of the breast cancers detected by screening were over-diagnosed. “Put simply, this means that one in five cancers do not pose a deadly threat, yet these women may still undergo treatment, including surgery, chemotherapy and radiation.” (OBOS)
    • A review concluded that “for every 2,000 women screened annually over 10 years, one life is prolonged but 10 healthy women are given diagnoses of breast cancer and unnecessarily treated, with therapies that themselves have life-threatening side effects.” (NY Times, 2013)
  • Cost: Although most private insurances and Medicare cover the majority of costs of mammogram, and thus individual consumers don’t pay much, the cost to society is high. About 38 million mammograms were performed in the US last year. (FDA) Average cost of a mammogram is $266. (Source.)

Benefit-Risk Ratio depends on the Age and Risk Status of the Individual Woman

The chance of getting breast cancer increases as we get older. The median age of diagnosis is 61. The median age of death is 68. So, screening in your 60s is much more likely to be worth doing (i.e. more likely to find a cancer that will benefit from treatment) than screening at a younger age. The chance of a 20 year woman getting breast cancer in the next ten years is only about .06%. (NY Times, 2013) So, screening is your 20s is not worth doing. (Even talking about breast cancer and breast self-exams with teenagers may just create fear and anxiety without giving benefit.)

What’s the tipping point for starting screening where benefits of screening outweigh the risks? And, what’s talked about less: at what age is it no longer relevant to screen for breast cancer? Let’s start with the recommendations for older women and work down.

Over 75 years of age: Screening may detect breast cancer. But the breast cancers women tend to get at this age are slow-growing. The older woman is more likely to die of other conditions before breast cancer would kill her. Treating a cancer at this age would cause risks and complications and not significantly lengthen life span. USPSTF

Age 50 – 75: There is general consensus that the benefits of screening outweigh the concerns.

Under 50: This is where the controversy lies.

For women who do have breast cancer, mammography increases the chance that will be found early and treated. The USPSTF says screening this age group led to a 15 percent decrease in mortality. The chairman of the USPSTF says: “If I take 1000 women over age 40, over their lifetimes, 30 will die from breast cancer if we do no screening. If I screen every one of those women beginning at age 50 until she’s 74, we reduce the deaths from 30 to 23.” He says if we start the screening in their forties, we might increase that by one additional life saved. (i.e. 22 would die)

However, the rate of false positives and over-treatment are higher for younger women. “Starting mammograms at 40 would mean having exams every two years for an average of 34 years. Over a lifetime, a woman’s chances of needing a biopsy to prove she didn’t have breast cancer might be as high as 50 percent.” (OBOS)

“The Cancer Society says for every 1,000 women in their 40s screened for 10 years, 600 will be called back for a repeat mammogram for something suspicious, 350 will get biopsied and about five will end up with a diagnosis of breast cancer. And some women might get treated for a cancer that would never have caused a problem.” http://www.npr.org/templates/story/story.php?storyId=130437187

Most experts say that between 40 and 50, the decision whether or not to screen is best made through a shared decision-making process between a woman and her physician / caregiver where they evaluate her risk factors, discuss the benefits and risks of screening, and assess her personal feelings about the screening – would it reduce her anxiety or increase it? For women at higher risk of breast cancer (see below), caregivers are more likely to recommend screening in their 40s (or, rarely, even younger than 40) versus they may recommend waiting until your 50s if you are at low risk.

Screening Recommendations

Here is my comparison of major recommendations, from: The Susan Komen Foundation, American Cancer Society (ACS), American Congress of Obstetricians and Gynecologists (ACOG), and the United States Preventive Services Task Force (USPSTF).

recommendations

* Breast Self Awareness and BSE: What to Look For

Women should be familiar with their breasts and, on occasion, check their appearance in a mirror and/o touch them to see if there are any unexplained changes. Women should remember that breast changes occur with pregnancy, breastfeeding, aging, menopause, during menstrual cycles, and when taking birth control pills or other hormones. It is normal for breasts to feel a little lumpy.

The Komen Foundation and American Cancer Society recommend that if you see these changes, check with your care provider:

  • Development of a lump – a thick hard knot inside the breast or under the arm
  • Swelling, warmth, redness, or skin irritation
  • Change in the size or shape of the breast; nipple pulling inward
  • Dimpling or puckering of the skin
  • Nipple discharge (other than breastmilk) that starts suddenly

** Risk Assessment

MRI recommendations say that it should be done in addition to mammogram, not instead of, and should be done only for women at high risk: those whose lifetime risk of breast cancer is 20 – 25% or higher.

Here are some guidelines from ACS and Komen Society on what factors would be assessed to determine high risk: A known BRCA1 or BRCA2 gene mutation or a first degree relative with one. Strong family history of breast cancer at age 45 or younger. A personal history of invasive breast cancer, DCIS, LCIS, or atypical hyperplasia. Radiation therapy to the chest between 10 and 30 years of age, Li-Fraumeni, Cowden, or Bannayan-Riley-Ruvalcaba syndromes.

How have benefits, risks, and survival rates changed over the years?

It is difficult to compare studies of how women have fared over the past 25 years with how they will fare over the next 25 years. Here are some factors that have changed breast cancer survival rates:

  • Awareness: Decades ago, breast cancer was not often spoken of. Women might have had lumps or other breast changes that they did not report to a physician until too late. As our society has talked about it more and more, it has raised awareness of the issue, which makes it more likely that women with concerning changes will seek treatment sooner.
  • Incidence: Increased screening has increased the number of cancers found. (i.e. the percentage of women who will receive a breast cancer diagnosis in their lifetime)
  • Understanding of breast cancer: We used to believe that most or all breast cancer was aggressive and would spread throughout the body if not detected and treated early. We now know there are several types of cancer found in the breast (NY Times, 2013), some of which are very slow growing or non-invasive, and some will disappear on their own. (NY Times, 2014) Thus, some of those extra diagnoses mentioned in the previous bullet point are likely to be of cancers that would never have developed into anything clinically significant.
  • Treatment has improved: There has been a 25% reduction in deaths since 1990, but it’s likely that is due to treatment, not to detection. (NY Times, 2013), Reductions in mortality are “more likely explained by changes in risk factors and improved treatment than by screening mammography.” BMJ.

Fear of Cancer, and the Politics and Economics of Breast Cancer Screening

Beyond the medical research and current guidelines, there are interesting cultural issues related to this topic which affect recommendations and affect whether women follow those recommendations.

What was the political response to the USPSTF guidelines?

“Rather than engaging in discussion about how to maximize the benefits of screening while minimizing its harms, Republicans seized on the panel’s recommendations as an attempt at health care rationing. The Obama administration was accused of indifference to the lives of America’s mothers, daughters, sisters and wives. Secretary Kathleen Sebelius of the Department of Health and Human Services immediately backpedaled, issuing a statement that the administration’s policies on screening “remain unchanged.” (NY Times, 2013)

How Do Women Feel about Screening Starting at Age 40?

After the USPSTF released their recommendations in 2009, a USA Today survey found that 76% of women disagreed with the recommendations. 84% of women age 35 – 49 said they would get a mammogram before age 50. 76% of women believed the panel recommended fewer mammograms because of cost, even though the panel only looked at medical benefits and risks.

The survey also showed again that women overestimate their risk of breast cancer. Whereas a 40-year-old woman’s chance of getting breast cancer in the next decade is only 1.4%, 40% of women think the chance is 20 – 50%.

Prophylactic mastectomy

Of women who have been diagnosed with cancer in one breast, there has been a significant increase in those opting for a double mastectomy. One study says they chose this to prevent having to face a second cancer (98%) and to improve chance of survival (94%). Even among women diagnosed with DCIS (a risk factor for cancer), there was a 188% increase from 1998 – 2005 in women choosing double mastectomy.

For women with a genetic predisposition to cancer, removing both breasts does not necessarily improve survival rates, and they were generally aware of that when making the decision.

For women who do not have a genetic predisposition, the chance of a cancer in the other breast is only 2 – 4 %, but those women tended to believe that the chance was 10%. In another study they estimated it at 30%. So, they may be basing their decision to have a double mastectomy on a fear-based over-estimation of the risk.

(Data combined from these sources: http://www.oncologynurseadvisor.com/young-women-overestimate-cancer-risk-in-second-breast/article/315231/ and NY Times 2013.)

Breast Cancer Charities may benefit from fears of breast cancer

A Susan Komen Foundation ad campaign from 2011 said “The 5-year survival rate for breast cancer when caught early is 98 percent. When it’s not? 23 percent.” Dr. Steven Woloshin from Dartmouth says this implies “[mammography] has this huge effect, and you’d have to be really irresponsible or crazy to not be screened.” (Huffington Post) But, Woloshin says the statistics are deceptive: “a woman in her 50s who goes for regular mammograms for 10 years will only cut her chance of dying by a fraction of a percentage point — for every 10,000 women who are screened 7 deaths will be prevented.” (MedicineNet)

Gayle Sulik, a sociologist, credits Komen (and other charities) for raising awareness of the disease, transforming “victims” into “survivors” and distributing over $1 billion to research and support. But she says “the function of pink-ribbon culture — and Komen in particular — has become less about eradication of breast cancer than self-perpetuation: maintaining the visibility of the disease and keeping the funds rolling in.” The Komen Foundation does have some vested interest in keeping awareness of breast cancer high. (NY Times, 2013) In 2012, CNBC reported that Komen’s annual income was around $340 million, and that Komen’s founder and CEO received an annual salary of $684,000, which is about a quarter million dollars higher than what is typical for a charity of that size.

Does anyone else have a vested interest in annual mammograms?

“[An] editorial in BMJ, “Too Much Mammography notes that it is difficult to make changes around screening mammography practices “because governments, research funders, scientists, and medical practitioners may have vested interests in continuing activities that are well established.” (OBOS) For example, the American College of Radiology, a trade organization for professionals who conduct and interpret mammograms, objected to recommendations to do mammograms less frequently.

Reducing your Risk of Breast Cancer

Obviously, no matter what screening approach you choose, we’re all hoping the results come back negative! What are some things you can do to increase that chance?

  • The more months of total breastfeeding in your life, the lower your risk.
  • Limit alcohol. No more than one drink a day.
  • Control your weight. Obesity, especially after menopause, increases your risk.
  • Don’t smoke. Smoking especially increases the risk of premenopausal breast cancer.
  • Limit hormone therapy for menopause related concerns. If you use, try the lowest possible dose that relieves your symptoms, keep use short-term (less than 3 years).
  • Minimize exposure to radiation and environmental toxins.
  • Exercise regularly.