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The Downside Of Screening Tests: The Costs Of False Positive Results
It’s easy to think of medical tests as black and white. If the test is positive, you have the disease; if it’s negative, you don’t. Even good clinicians sometimes fall into that trap. Based on the pre-test probability of the disease, a positive test result only increases the probability by a variable amount. An example: if the probability that a patient has a pulmonary embolus (based on symptoms and physical findings) is 10% and you do a D-dimer test, a positive result raises the probability of PE to 17% and a negative result lowers it to 0.2%.
Even something as simple as a throat culture for strep throat can be misleading. It’s possible to have a positive culture because you happen to be an asymptomatic strep carrier, while your current symptoms of fever and sore throat are actually due to a virus. Not to mention all the things that might have gone wrong in the lab: a mix-up of specimens, contamination, inaccurate recording…
Mammography is widely used to screen for breast cancer. Most patients and even some doctors think that if you have a positive mammogram you almost certainly have breast cancer. Not true. A positive result actually means the patient has about a 10% chance of cancer. 9 out of 10 positives are false positives.
But women don’t just get one mammogram. They get them every year or two. After 3 mammograms, 18% of women will have had a false positive. After ten exams, the rate rises to 49.1%. In a study of 2400 women who had an average of 4 mammograms over a 10 year period, the false positive tests led to 870 outpatient appointments, 539 diagnostic mammograms, 186 ultrasound examinations, 188 biopsies, and 1 hospitalization. There are also concerns about changes in behavior and psychological wellbeing following false positives.
Until recently, no one had looked at the cumulative incidence of false positives from other cancer screening tests. A new study in the Annals of Family Medicine has done just that.
They took advantage of the ongoing Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial to gather their data. In this large controlled trial (over 150,000 subjects), men randomized to screening were offered chest x-rays, flexible sigmoidoscopies, digital rectal examinations and PSA blood tests. Women were offered CA-125 blood tests for cancer antigen, transvaginal sonograms, chest x-rays, and flexible sigmoidoscopies. During the 3-year study period, a total of 14 screening tests were possible for each sex. The subjects didn’t all get every test.
By the 4th screening test, the risk of false positives was 37% for men and 26% for women. By the 14th screening test, 60% of men and 49% of women had had false positives. This led to invasive diagnostic procedures in 29% of men and 22% of women. 3% were minimally invasive (like endoscopy), 15.8% were moderately invasive (like biopsy) and 1.6% involved major surgical procedures (like hysterectomy). The rate of invasive procedures varied by screening test: 3% of screened women underwent a major surgical procedure for false-positive findings on a transvaginal sonogram.
These numbers do not include non-invasive diagnostic procedures, imaging studies, office visits. They do not address the psychological impact of false positives. And they do not address the cost of further testing.
These data should not be over-interpreted. They don’t represent the average patient undergoing typical cancer screening in the typical clinic. But they do serve as a wake-up call. Screening tests should be chosen to maximize benefit and minimize harm. Organizations like the U.S. Preventive Services Task Force try to do just that; they frequently re-evaluate any new evidence and offer new recommendations. Data like these on cumulative false positive risks will help them make better decisions than they could make based on previously available single-test false positive rates.
“In a post earlier this year, I discussed the pros and cons of PSA screening. Last year, I discussed screening ultrasound exams offered direct to the public to bypass medical judgment). If you do 20 lab tests on a normal person, statistically one will come back false positive just because of the way normal lab results are determined. Figuring out which tests to do on a given patient, either for screening or for diagnosis, is far from straightforward.
This new information doesn’t mean we should abandon cancer screening tests. It does mean we should use them judiciously and be careful not to mislead our patients into thinking they offer more certainty and less risk than they really do.
*This blog post was originally published at Science-Based Medicine*
Healthcare Costs: Under-Thinking Leads To Over-Testing
My mother-in-law just had a CT scan of her head in the Emergency Department of her local hospital. My husband called me to ask if I could “talk to her about her headache.”
Severe headaches in the elderly are indeed worrisome, and I wondered if she had fallen recently – if she might have a bleed in her brain requiring immediate surgery. Of course, she’d need a CT scan to rule that out… I was prepared for the worst. But what I learned by simply talking to Mrs. Zlotkus was unexpectedly revealing – not only about her diagnosis but about our healthcare system in general.
As it turns out, Mrs. Zlotkus had been having severe headaches for about 3 months. She was taking Vicodin daily to “take the edge off.” When I asked her about the location of the pain, she said that it was “just on one side of my head, from the top of my neck to the top of my head.” I asked her if the pain sometimes traveled to the other side, or if it involved her eye. “Never,” was her quick response. She also told me that she’d been seeing a physical therapist for 2.5 months for neck stretching exercises.
Mrs. Zlotkus told me her CT scan was negative, and that her blood tests didn’t show any “temporary arthritis.” (That’s temporal arteritis, I presume.)
“Well,” I said, “There’s only one thing left that I can think of that will give you a headache in the exact area you’re describing – and that’s shingles. Did you notice any scabs or painful bumps on your scalp when the headaches first started?”
“Why, yes!” Said Mrs. Zlotkus. “About 3 months ago I noticed some very painful, crusty scabs on my scalp. I thought for sure it was because my hairdresser used extra strong chemicals on my hair. I scolded her for it. She told me to put tea tree oil on it.”
Oh, boy. There it was – a diagnosis as plain as the nose on her face.
“Um… Well did you tell the ER docs about the scabs?”
“No. They never asked me about it and I didn’t see what my hairdresser’s chemical burn had to do with my severe headaches.”
My mother-in-law’s work up (ER visit, CT scan, several doctor visits, pain medicines), misdiagnosis (neck muscle stiffness), and mistreatment (physical therapy) for shingles probably cost upwards of $10,000. Worse than that, she did not get anti-viral treatment early enough in her outbreak to prevent a long-lasting pain syndrome (called post-herpetic neuralgia). Now that she has this shingles-related headache, it’s very hard to treat. And taking lots of acetaminophen-rich medications (Vicodin) is the last thing her liver needs right now.
So how did the healthcare system fail Mrs. Zlotkus? In my opinion, this is a great example of the “failure of synthesis” that Evan Falchuk discusses on his See First blog. Somehow, the physicians involved in Mrs. Zlotkus’ care didn’t take the time to think about her symptoms, to ask the right questions, and to put all the puzzle pieces together. Instead, they just ruled out the potential emergency issues (a stroke/hemorrhage, or temporal arteritis) and gave her a follow up appointment with a neurologist (who couldn’t fit her in their schedule for 2 months). They didn’t take a full history – they just dumped her in the most likely diagnostic category (neck stiffness) and let some other specialist follow up. Shameful.
I’ve described more egregious examples of hasty medical care on this blog – consider the case of an elderly woman (the mother of a friend of mine) who was misdiagnosed with “end stage dementia” when she really had acute delirium from an overdose of diuretics… Or the case of my girlfriend who was mistaken in the ER for a drug seeker when she was suffering from a kidney stone.
Sometimes I feel as if I have to keep an eye on all my friends and family before they set foot in a hospital, ER, or doctor’s office. I’m afraid that those providing their care will be so rushed and thoughtless that my loved ones will wind up with a huge bill, the wrong diagnosis, and perhaps even a near-death experience. I am seriously afraid for them.
The bottom line is that we have to stop rewarding providers for volume over quality. We have to value the history and physical exam beyond the CT scan and lab tests. We have to give doctors the chance to think about their patients – rather than turn up the speed dial on the clinical treadmills as a means to reduce costs.
My mother-in-law just spent $10,000 of our tax dollars on a diagnosis that could be made in 5 minutes of thoughtful questioning over the telephone. Multiply that cost by the number of other Medicare beneficiaries who are suffering similar misdiagnoses in this country and we’re talking serious money.
Under-thinking leads to over-testing. Has the CBO taken that into consideration in its scoring of various reform plans? I don’t think so. To me, this is yet another reason why we need physicians at the table in healthcare reform – we see the real cost drivers that others might not think of – even if some of us are too busy to diagnose shingles correctly!
Ezra Klein Recommends Cutting Medicare Payments To Inner City Hospitals?!
First of all, just for the record, let it be noted that my previous post was entirely about Medicare’s under-reimbursement of physicians, and Ezra’s clearly going all Willie Sutton and going where the real dollars are: facility reimbursement. Fair enough, though I’ll disclaim that I’m not nearly as well-versed in hospital reimbursement as I am in the professional side of the Medicare fee schedule.
The above graph would seem to disprove Ezra’s original thesis, that hospitals continue to participate in Medicare because it is profitable for them to continue to do so. As you can see, there’s rampant cost shifting, as Medicare pays only 92% of the actual costs of inpatient care whereas the commercial payers are in the high 120s%. Right?
Well, yes and no. The lifeline in this case is some very interesting testimony by the head of MedPac regarding a small subset of hospitals (about 12% of all hospitals) who were actually able to eke out a positive margin (0.5%) on Medicare payments in 2004-2006. The contention is that since these hospitals were able to do so, and with higher quality than the other 88% of hospitals, that the hospital industry in general is inefficient and if they were only able to get their act together Medicare payments would be sufficient to support a viable hospital industry.
The key factor which Ezra glides over is that these hospitals are in the “financially pressured” category. There doesn’t seem to be a definition or cross-tabs on what exactly “financially pressured” means, but these hospitals actually have a worse operating margin on their non-medicare business (-2.4%). Given that, it’s fairly safe to conclude that this means hospitals with crummy payer mixes — high medicaid and uninsured, low numbers of commercially insured patients. This occurs most commonly in rural and inner-city markets — underserved areas in which there is usually one hospital at best. These undesirable markets do not encourage other providers to enter and compete for customers and so the hospitals there tend to undercapitalize, willfully or no, and offer bare-bones services. That some fraction of “financially pressured” over-perform on outcomes is not explained in the testimony. It could be a statistical aberration, or cherry-picked data; giving credit to the integrity of MedPac, it might be due to the exceptional leadership that some of these financially stressed hospitals have developed. The testimony does not reveal what fraction of “financially pressured” hospitals outperform on quality measures — if less than 50% of “financially pressured” hospitals outperform on quality, it would imply that the under-funding of these facilities harms quality of care more than it helps. Note that those that outperform have substantially worse margins (0.5% vs 4.2) on Medicare payments, implying that there is some linkage between higher expenditures and better outcomes.
I am gallant, however, and I will concede the key point here: hospitals which are well-funded do tend to be inefficient. Specifically, areas with enviable payer mixes are generally served by multiple hospitals and those hospitals compete for patients and revenue by over-capitalizing and improving amenities and customer service. This is just another example of the perversion of the market in which patients do not directly bear the costs of their health care decisions.
Coming back to the original point: if Medicare were such a lousy payer, hospitals would opt out, yet this never occurs. Interestingly, the well-heeled suburban hospitals who lose the most money on Medicare patients are the least likely to opt out of Medicare. They have such high margins on their commercial patients that they can view Medicare as their charity contribution to the community. On the other hand, the financially pressured hospitals do better on Medicare than the rest of their payers, so Medicare is their economic lifeline. Or, more formally, the value of Medicare patients to a hospital varies inversely with the number of commercial patients in their payer mix.
Ezra’s conclusion here is that we need to cut costs, hospitals are in many cases inefficient, and so we should just reduce payments to them until they feel the pain and dial it way back. As my old medical director used to say, “We’re building a Buick, not a Cadillac.” But there are many problems with such a strategy. For one, the hospitals most dependent on Medicare would be harmed most by reductions in payments. While workarounds could be crafted for financially stressed hospitals, it’s unclear what effect reductions in payments would have in quality, but it would be hard to imagine that quality in general would improve. And it’s not clear to me that this really addresses the key drivers of cost: wasteful and redundant care, as opposed to more-expensive-than-it-needs-to-be inefficient care. Given the volume incentive of the fee-for-service game, reductions in compensation usually just drive increases in utilization, not the other way around.
Ultimately on this point, I have to concede ignorance. I know that the Medicare Professional Fee Schedule for phyicians is woefully inadequate and needs to be increased. I do not know if the same applies to the hospital fee schedule — I’m just not well-enough versed in the economics of that game. I should point out that while medicare payments to physicians have been essentially frozen since 2001, the facility fees, unconstrained by the SGR, have risen year over year to keep pace with inflation. I never did see any disagreement with my original points, by the way, that for professional services, the underfunding of Medicare is leading to decreased access as physicians close their practices to new Medicare patients, and that hospital-based physicians are unable to opt out due to the nature of their relationships with the hospitals who employ them.
*This blog post was originally published at Movin' Meat*
We’ve Tried Single-Payer Healthcare, And It Has Failed
Contrary to what you may have been led to believe, the United States has already tried its hand at a pseudo-single-payer system. The VA is one example. Another, albeit less highly publicized, is the Indian Health Service. (via WhiteCoat)
Based on an agreement in 1787, the government is responsible to provide free health care to Native Indians on reservations. And, as you can see from this scathing story from the Associated Press, that promise has not been kept.
The numbers don’t lie:
American Indians have an infant death rate that is 40 percent higher than the rate for whites. They are twice as likely to die from diabetes, 60 percent more likely to have a stroke, 30 percent more likely to have high blood pressure and 20 percent more likely to have heart disease.American Indians have disproportionately high death rates from unintentional injuries and suicide, and a high prevalence of risk factors for obesity, substance abuse, sudden infant death syndrome, teenage pregnancy, liver disease and hepatitis.
And, after Haiti, where in the Western hemisphere do men have the lowest life expectancy? It’s on Indian reservations in South Dakota.
The primary reason, not surprisingly, is lack of money, compounded by a difficult time recruiting physicians and other clinicians. Indeed, many Indian health clinics cannot “deal with such high rates of disease, and poor clinics do not have enough money to focus on preventive care.”
So, if you’re in the camp that supports a Medicare-for-all-type solution to our health care woes, consider how that same government, whom you’re entrusting to be the single-payer, has neglected the Indian Health Service.
*This blog post was originally published at KevinMD.com*