Oft expectation fails, and most oft where most it promises;
and oft it hits where hope is coldest; and despair most sits.
~William Shakespeare
.
Screening asymptomatic men for PSA (prostate specific antigen) does more harm than good.
Ten years of screening healthy men for PSA (prostate specific antigen) as a marker for prostatic cancer has not reduced the death rate from cancer of the prostate (still very low). This single blood test has resulted in a lot of money and time spent for diagnostic tests (biopsies and their complications which “are not trivial”), physician office visits, and aggressive therapy which have been of little benefit to patients.. Even when a biopsy confirms the presence of prostate cancer in a high-PSA patient, there is very little evidence that there is any benefit in treating the patient that has a normal physical exam (digital rectal examination) and normal prostatic volume by ultrasound. While still controversial, recommendations from the U.S. Preventative Service Task Force include “just wait and see” if there is a bump in your annual PSA. If you as a patient can’t tolerate that, it is probably better to ask your physician to skip the blood test.
Screening for lung cancer with an annual chest x-ray doesn’t help either.
A thirteen year study of 155,000 people showed no difference in mortality rates between those who got annual chest x-rays and those who did not. In fact, 95% of the people with “positive findings” on x-ray did NOT have lung cancer. Low-dose CAT scanning of the lung may be a better screening tool, but the jury is still out on that.
What about the screening blood test (CA 125) for often-silent and frequently lethal ovarian cancer?
In a twelve and a half-year study of 68,000 U.S. women screened for ovarian cancer with a CA 125 blood level and vaginal ultrasound the women who were screened did no better in terms of earlier diagnosis, reduction in mortality, or increased longevity after diagnosis than those who were not screened. Serial measurement of CA 125 can be helpful in monitoring tumor activity in patients already diagnosed and treated for ovarian cancer, but it is of no benefit as a screening tool for ovarian cancer. Large scale clinical trials outside the U.S. are currently seeking confirmation or refuting of this viewpoint.
The vaccine against shingles (herpes zoster) is about 50% effective.
A large observational study of people who received the zoster vaccine confirmed that in the “real world”, as in the laboratory, about one-half of vaccine recipients were protected from developing the condition. In the natural course of shingles without the vaccine about 6% of people who have had shingles in the past have a recurrence within 8 years. Presumably the vaccination of someone who has had shingles in the past could reduce the recurrence rate by half to 3%. As with all medical statistics, of course, if you get shingles it is 100% for you.
If you get a mammogram every year for 10 years the chances of having a “false positive” finding is 50%.
During ten years of study of 160,000 women receiving either annual or biennial mammograms about half of the women during the 10 year period had at least one false positive finding; a non-cancerous abnormality that led to additional imaging without a biopsy. The probability that a false positive finding during the 10 years of annual testing led to a biopsy was about 7%.
Lowering cholesterol levels in the elderly can increase their mortality rate.
A 14-year study of nearly 6000 men with an average age of 69 showed that those with higher cholesterol had LESS non-cardiovascular and less cancer-associated deaths. There was NO association between a higher cholesterol and increased cardiovascular death rates in those men between 55 and 84 years of age. In those over 85 years old a HIGHER cholesterol level was associated with a LOWER death rate from cardiovascular disease. This means that cholesterol lowering medications (statins) are unnecessary for elderly with low coronary risk factors. So, if you or a family members are over 70 and have high cholesterol, just live with it and don’t take statins. You may live longer.
MRIs give lots of false positives in people with non-specific low back or shoulder pain.
A 1994 study of 98 normal people without back pain showed that 2/3 of them had significant and “potentially serious” findings suggesting back pain on their MRIs. But, they had no pain or other back symptoms. A more recent study of 31 professional baseball pitchers revealed that 90% had abnormal cartilage by MRI in their pitching shoulder; findings considered indications for surgery. But, none of the pitchers had shoulder symptoms, and all were in excellent health.
Lyme blood tests are misleading a lot of the time.
Guidelines for diagnosing Lyme disease by laboratory test requires a positive test of the same blood sample using two different techniques, one an “enzyme assay” (ELISA) and one an “immune blot”. The laboratory diagnosis of Lyme disease requires a positive test with both techniques. A Dutch study of 89 patients with suspected Lyme, syphilis, or mycoplasma pneumonia revealed a significant amount of cross reactivity (falsely positive Lyme test in those that had syphilis or mycoplasma pneumonia). Many samples from suspected Lyme patients had a positive ELISA test with only one of the eight commercial labs providing the test. Some tested negative on ELISA but had positive immune blot tests, and visa versa. Only 16 of the 89 had positive ELISA tests with all 8 laboratories. This inconsistency of results confirms the opinion of infectious disease clinicians that the diagnosis of Lyme disease is a clinical judgement, not a laboratory one. Reassuringly, all healthy people tested in this study had negative Lyme test results.
References:
1. Three PAS viewpoints, NEJM Nov. 24, 2011 and Year in Review 2011, Journal Watch Gen Med, pg.4 Jan 1, 2012.
2. Chest X-rays for lung cancer, NEJM Aug. 4, 2011 and JAMA Nov. 2, 2011 and Year in Review, Jour Watch Gen Med, pg.5 Jan. 1, 2012.
3. CA 125 in Ovarian Cancer, JAMA June 8, 2011.
4. Shingles vaccine, JAMA Jan 12, 2011 and Mayo Clin Proc February 2011
5. Mammogram false positives, Ann Int Med 2009; 151:716
6. High Cholesterol, J Am Geriatric Soc, Oct 2011
7. MRIs false positives, Wired, January 2012, pg.108
8. Lyme tests, Eur J Clin Microbiol Inf Dis, Aug 2011
HUB's LIST of medical fun facts 