Medical Mythology

I. What is a “Medical Myth”?
Things we are taught that are just plain wrong.

II. Who are the Perpetrators?
A. In training
1. Faculty
2. Attendings
3. Senior residents

4. Other students - powerful vectors!
B. In practice
1. Consultants
2. Ourselves

III. How do Medical Myths develop?
A. The “Plausible Theory” model
1. It makes pathophysiologic sense, so it must be true

2. Myth: Treat acute otitis media in children with antibiotics to hasten resolution of pain and fever, and to prevent complications such as perforation, chronic effusion, recurrent acute otitis media and supperative complications.
3. Reality: Antibiotics offer only minimal or modest benefit with respect to pain and fever short term, and minimal or no benefit in pain, fever and significant complications beyond 48 hours. At best, the NNT is around 8.
Management of Acute Otitis Media. Summary, Evidence Report/Technology Assessment: Number 15, June 2000. Agency for Healthcare Quality and Research, Rockville, MD. [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]
B. The “Lazy I” model (A corollary of the “Plausible Theory” model)
1. It ought to work, and it sure is easy

2. Myth: Sliding scale insulin is effective and appropriate therapy for managing diabetes in the hospital.
3. Reality: Although sliding scale insulin regimens are prescribed for the majority of inpatients with diabetes, they appear to provide no benefit; in fact, when used without a standing dose of intermediate-acting insulin, they are associated with an increased rate of hyperglycemic episodes.
Queale WS et al, Glycemic control and sliding scale insulin use in medical inpatients with diabetes mellitus, Arch Intern Med 1997 Mar 10; 157(5): 545-52. PMID: 9066459
C. The “Dogma” model (AKA “The Blind Leading the Blind” model)
1. If the experts say so, it must be true

2. Myth: Narcotics can mask the signs and symptoms of an acute abdomen. (Cope’s Early Diagnosis of the Acute Abdomen, 1983)
3. Reality: Early administration of opiate analgesia to patients with acute abdominal pain can greatly reduce their pain. This does not interfere with diagnosis, which may even be facilitated despite a reduction in the severity of physical signs.
Attard AR et al, Safety of early pain relief for acute abdominal pain, BMJ 1992 Sep 5; 305(6853): 554-6. PMID: 1393034
D. The “Bad Research” model
1. Poor early research (e.g., non-RCT (often single case report!), no comparison arm (e.g., Swann-Ganz catheter), small number of subjects) suggested the myth, or
2. Initial research to refute the myth was poorly done (e.g., inadequate dosage of medication)
3. However, subsequent, more rigorous research has successfully refuted the myth

4. Myth: Vitamin B12 deficiency due to pernicious anemia cannot be treated orally.
5. Reality: In cobalamin deficiency, 2 mg of cyanocobalamin administered orally on a daily basis was as effective as 1 mg administered intramuscularly on a monthly basis and may be superior.
Kuzminski AM et al, Effective treatment of cobalamin deficiency with oral cobalamin, Blood 1998 Aug 15; 92(4): 1191-8. PMID: 9694707

E. The “Bad Researcher” model (Researcher interpretation bias)
1. "We've Shown Something Here" bias - Interpretation tainted by the researchers' enthusiasm for a positive result
2. "The Result We've All Been Waiting For" bias - The clinical and scientific communities' prior expectations (both medical and non-medical, e.g. political)
3. "Just Keep Taking the Tablets" bias - The tendency for clinicians to overestimate the benefits and underestimate the harms of drug treatment
4. "What The Hell Can We Tell The Public" bias - The political need for regular, high impact breakthroughs
5. "If Enough People Say It, It Becomes True" bias - The subconscious tendency for reviewers and editorial committees to "back a winner"

6. Myth: The United Kingdom Prospective Diabetes Study (UKPDS) of 5000+ patients followed over 20 years, showed:
a. Hyperglycemia in Type II diabetes is a continuous, modifiable risk factor for clinically important outcomes and that reduction in glucose is the key to improving outcomes
b. Tight blood glucose control is an important goal in Type II diabetes
c. Intensive treatment of Type II diabetes is beneficial
7. Reality: A closer and more objective look at the UKPDS data clearly shows:
a. The medications used (glibenclamide, chlorpropamide and/or insulin) to lower blood glucose concentrations produced no significant benefit on any single macrovascular end point for any group of patients
b. Metformin reduced progression of retinopathy and reduced the frequency of the aggregated diabetes-related endpoints, all cause mortality, and stroke compared with the sulphonylureas and insulin or diet alone
c. The benefit of metformin is not necessarily related to its hypoglycemic effect
d. Decreasing HgbA1c using medication did not improve any clinical endpoint
McCormack J, Greenhalgh T, Seeing what you want to see in randomised controlled trials: versions and perversions of UKPDS data, BMJ 2000 June 24, 320:1720-3. PMID: 10864554
Shaughnessy AF, Slawson DC. What happened to the valid POEMs? A survey of review articles on the treatment of type 2 diabetes. BMJ 2003 Aug 2; 327(7409): 266. PMID: 10864554

IV. Why are Medical Myths so resistant to change?
A. Particularly Persuasive Pearls of Punditry: They have the
a. Ring of truth
b. Aura of wisdom
c. Flavor of logic
B. Knowledge inertia
1. We mostly practice what we learned in medical school and residency
2. Supplemented by experiential learning
3. As adults, we don’t learn well from CME courses, home study and journal reading

C. Medical Myths are Memes
1. Memes are self-replicating units of culture that have a life of their own. (Dawkins, The Selfish Gene, 1976)
2. Examples: Tunes, ideas, catchphrases, fashions, ways of making French toast or driving screws, techniques for diagnosis and treatment
3. “Memes (discrete units of knowledge, gossip, jokes and so on) are to culture what genes are to life. Just as biological evolution is driven by the survival of the fittest genes in the gene pool, cultural evolution may be driven by the most successful memes.” (Dawkins, Time Magazine, 1999)
4. Memes are “viral” as they infect a culture like medicine
a. Spontaneous generation (more probably mutation from other medical concepts)
b. Evolution from pathophysiologic principles
c. Horizontal spread - throughout the medical education culture
d. Vertical spread - down through generations of health professionals
e. Like a virus, a meme can live forever (e.g., “Democracy”)

V. Some examples of medical myths:

A.Myth: Rectal temperature can be accurately estimated by adding 1°C to the temperature measured at the axilla.
Reality: In children and young people temperature measured at the axilla does not agree sufficiently with temperature measured at the rectum to be relied on in clinical situations where accurate measurement is important.
Craig JV et al, Temperature measured at the axilla compared with rectum in children and young people: systematic review. BMJ 2000 April 29; 320:1174-1178. PMID: 10784539

B.Myth: In asthma, a nebulizer is a more effective way to deliver medication than is a metered dose inhaler (MDI) with spacer.
Reality: A MDI with a spacer for the administration of albuterol is at least as effective as a nebulizer in children and adults with acute and stable asthma.
Ram FS et al. Systematic review of clinical effectiveness of pressurised metered dose inhalers versus other hand held inhaler devices for delivering beta (2 ) agonists bronchodilators in asthma. BMJ. 2001 Oct 20;323(7318):901-5. PMID: 11668134

C.Myth: A urinary tract infection in a young man requires evaluation with imaging and other studies.
Reality: Extensive evaluation appears unnecessary for young men with bacteriuria who respond to antimicrobial therapy.
Krieger JN et al, Urinary tract infections in healthy university men. J Urol 1993 May; 149(5): 1046-8. PMID: 8483206

D.Myth: Prenatal care clearly improves pregnancy outcome.
Reality: From a meta-analysis of 50 studies involving 669,876 women, prenatal care has not been demonstrated to improve birth outcomes conclusively.
Fiscella K, Does prenatal care improve birth outcomes? A critical review, Obstet Gynecol 1995 Mar; 85(3): 468-79. PMID: 7862395


E.Myth: The bimanual pelvic exam provides useful information when evaluating gynecologic disease
Reality: The literature suggests that it is unwise to base decisions on a clinical examination of the female pelvis, regardless of the practitioner's level of experience. A positive examination may raise the probability of disease but does not ensure the diagnosis. A negative examination certainly does not rule out disease. The idea that the clinical examination of the female pelvis is an adequate, reliable and reproducible method for evaluating significant pelvic pathology is a dangerous myth.
Brown T, Herbert ME, Medical myth: Bimanual pelvic examination is a reliable decision aid in the investigation of acute abdominal pain or vaginal bleeding. Can J Emerg Med 2003 Mar; 5: 120-22. [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]

F.Myth: Antibiotics decrease the effectiveness of oral contraceptives (OCs).
Reality: The difference in failure rates of OCs when taken concurrently with common antibiotics versus OC use alone suggests that these antibiotics do not increase the risk of pregnancy.
Helms SE et al, Oral contraceptive failure rates and oral antibiotics. J Am Acad Dermatol 1997;36:705-10s. PMID: 9146531
Burroughs KE, Chambliss ML, Antibiotics and oral contraceptive failure, Arch Fam Med. 2000 Jan; 9(1):81-2. PMID: 10664647

G.Myth: The most cost-effective treatment strategy for urinary tract infection in young women is full urinalysis and culture.
Reality: For the treatment of UTI in symptomatic young women, the following strategies are listed in order of decreasing cost-effectiveness:
•Most cost-effective (least expensive) strategy:
oEmpirical treatment of symptomatic women
•Less cost-effective (more expensive) strategy:
oTreatment based on full urinalysis
oTreatment with office culture to confirm sensitivity
oTreatment with reference lab culture to confirm sensitivity
oTreatment after office culture results available
oTreatment after reference lab results available
•Least cost-effective (most expensive) strategy:
oTreatment based on dipsticks
Barry HC et al, Evaluation of suspected urinary tract infection in ambulatory women: A cost-utility analysis of office-based strategies. J Fam Pract 1997;44:49-60. PMID: 9010371
Fenwick EA et al, Management of urinary tract infection in general practice: a cost- effectiveness analysis. Br J Gen Pract 2000 aug; 50(457): 635-9. PMID: 11042915
Saint S et al, The effectiveness of a clinical practice guideline for the management of presumed uncomplicated urinary tract infection in women, Am J Med, 1999; 106 (6): 636-641. PMID: 10378621

H.Myth: These tests have all been shown to be useful screening tests (i.e., improve survival) in asymptomatic adults:
Chest X-ray in older patients, smokers and travelers
Hemoglobin for anemia
ESR for inflammatory, infective or malignant disease
Liver function tests in blood
Renal function tests
Calcium in blood
Uric acid in blood
Glucose in blood
Cholesterol
HDL/LDL ratio
Mammography in women over 40 years
Ultrasound examination of the ovaries
Bone density in women
Resting ECG
Exercise ECG on a treadmill
Ultrasound examination of the aorta in men over 55 years
PSA in men over 50 years
Helicobacter pylori
Reality: There is no scientific evidence supporting the value of these studies as screening tests in asymptomatic populations.
Evidence-Based Journalism. Bandolier Jun 1995; 16-5. [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]
I.Myth: Bed rest is a useful adjunctive therapy.
Reality: A meta-analysis of 39 studies of the use of bed rest versus early mobilization for prevention and treatment of a variety of medical conditions showed bed rest to be at best not beneficial and at worst harmful.
Allen C et al, Bed rest: a potentially harmful treatment needing more careful evaluation, Lancet 1999 Oct 9; 354(9186): 1229-33. PMID: 10520630

J.Myth: COX-2 inhibitors are more effective and have far fewer GI side effects than earlier NSAIDs.
Reality: COX-2 inhibitors produced similar results with respect to symptom control and withdrawl rates for adverse effects as with other NSAIDs.
McCormack J, Rango R. Digging for data from the COX-2 trials. CMAJ. 2002 Jun 25;166(13):1649-50. PMID: 12126315.
Wooltorton E, What's all the fuss? Safety concerns about COX-2 inhibitors rofecoxib (Vioxx) and celecoxib (Celebrex). CMAJ. 2002 June 25; 166 (13). PMID: 12126328

K.Myth: Niacin can aggravate blood sugar control and should not be used in hyperlipidemic diabetics.
Reality: Lipid-modifying dosages of niacin can be safely used in patients with diabetes. Niacin therapy may be considered as an alternative to statin drugs or fibrates for patients with diabetes in whom these agents are not tolerated or fail to sufficiently correct hypertriglyceridemia or low HDL-C levels.
Elam MB et al. Effect of niacin on lipid and lipoprotein levels and glycemic control in patients with diabetes and peripheral arterial disease: The ADMIT study: A randomized trial. JAMA 2000 Sept 13; 284(10): 1263-70. PMID: 10979113

L.Myth: Pulmonary artery catheterization is useful for diagnosing and managing shock and acute respiratory distress syndrome.
Reality: Clinical management involving the early use of a pulmonary artery catheter in patients with shock, ARDS, or both did not significantly affect mortality and morbidity.
Richard C et al. Early use of the pulmonary artery catheter and outcomes in patients with shick and acute respiratory distress syndrome: A randomized controlled trial. JAMA 2003 Nov 26; 290: 2713-2720. PMID: 14645314

M.Myth: Stretching before and after exercise decreases muscle soreness, prevents injury, and improves exercise performance.
Reality: Stretching before or after exercising does not confer protection from muscle soreness. Stretching before exercising does not seem to confer a practically useful reduction in the risk of injury, but the generality of this finding needs testing. Insufficient research has been done with which to determine the effects of stretching on sporting performance.
Herbert RD, Gabriel M. Effects of stretching before and after exercising on muscle soreness and risk of injury: Systematic review. BMJ 2002 Aug 31; 325(7362): 468. PMID: 12202327

N.Myth: Hand lacerations require suturing for proper healing.
Reality: Similar cosmetic and functional outcomes result from either conservative treatment or suturing of small (<2cm) uncomplicated lacerations of the hand, but conservative treatment is faster and less painful.
Quinn J et al. Suturing versus conservative management of lacerations of the hand: Randomised controlled trial. BMJ 2002 Aug 10; 325(7359): 299. PMID: 12169503

O.Myth:"Figure-of-Eight" dressings or similar appliances are the preferred treatment for clavicle fractures.
Reality:No statistical difference was found in the speed of recovery when clavicle fractures were treated by either a figure-of-eight bandage or broad arm sling.
Stanley D, Norris SH, Recovery following fractures of the clavicle treated conservatively. Injury 1988 May; 19(3): 162-4. PMID: 3248891

P.Myth: Antidepressant medications provide significant and unique benefits in treating depression.
Reality: From a meta-analysis of 19 studies of 2318 patients treated with antidepressants for depression, the response to inert placebos is approximately 75% of the response to active antidepressant medication. Whether the remaining 25% of the drug response is a true pharmacologic effect or an enhanced placebo effect cannot yet be determined.
Kirsh I, Sapirstein G. Listening to Prozac but hearing placebo: A meta-analysis of antidepressant medication. Prevention & Treatment 1998 June 26; v1, Article 00002a [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]
Kirsh I et al. The emperor’s new drugs: An analysis of antidepressant medication data submitted to the U.S. Food and Drug Administration. Prevention & Treatment 2002 July 15; V5, Article 23. [ندعوك للتسجيل في المنتدى أو التعريف بنفسك لمعاينة هذا الرابط]

Q.Myth: The size of a man’s penis can be estimated from his shoe size.
Reality: The supposed association of penile length and shoe size has no scientific basis.
Shah J, Christopher N. Can shoe size predict penile length? BJU Int 2002 Oct; 90(6): 586-7. PMID: 12230622