Why the scientific literature is important
Why the scientific literature is important
? New knowledge generated by RCTs takes 17 years to be incorporated into practice (Institute of Medicine)
? Hodgkin ? Prior to 1970: 5-10% for 4 year survival ? 1970 study: 80% complete remission ? 11 years before results were disseminated
? Testicular cancer ? Cure rate 80% ? 3 years before results were disseminated
Concordance between clinical practice and published evidence Findings from The National Dental Practice-Based Research Network JADA 2014
But many readers do not know how to assess the evidence critically, she said. "To be completely honest, probably it does have a big impact because most people who use the literature are not accustomed to doing critical analysis of it."
Medscape Medical News > Conference News Conflicts of Interest Prevalent in Dental Research Laird Harrison March 27, 2013
1
Levels of Evidence
1906: Pure Food and Drug Act
? Product Labeling
? Cocaine ? Opiates ? Alcohol
? Electricity
1938: Federal Food, Drug, and Cosmetic Act
? diethylene glycol led to over a hundred deaths ? mostly children
? "The Radium water worked fine until his jaw came off" WSJ, 1932
1962: Kefauver-Harris Amendment
1976: Medical Device Amendment
? Dalkon Shield? 3
? TMJ implants: "... a new era in (ProplastTeflon) TMJ reconstruction has begun, resulting in increased benefits to the patients whom we all serve."
"GRASSLEY SECURES INDEPENDENT REVIEW OF FDA
APPROVALS"
? Torcetrapib (2006) raises HDL
? Avandia (2007) controls blood glucose
? Vytorin (2008) lowers cholesterol
? Trasylol (2008) lowers bleeding
Senator Charles Grassley (R, Idaho) Picture from Washington Post
2
50% failure rate at 6 years "One of the biggest disasters in orthopedic history" BMJ
1
SR of RCTs
RCT
All-or-none
SR cohort studies
2
Cohort studies
Ecological studies
3
SR case-control studies Case-control study
Case-reports and case-series
Expert opinion, Biological plausibility, Animal evidence, Bench research
Perio No tx
Pre-term
+
-
280(12.6%) 1948
2228
261(11.7%) 1968 2229
Randomized Controlled Trial
CHX
R
Placebo
tooth loss No tooth loss
tooth loss No tooth loss
3
Randomized Trial on Tooth Loss
? 1101 elders ? Randomly assign to
CHX (550) or placebo (551) ? Followed for 4.4 years ? Results:
? CHX: 14 teeth/1000 tooth-years
? Placebo: 13.7/1000 tooth-years
RCT Pre-natal fluoride/caries
Pre-natal F
caries caries-free
30
368
398
7.5%
Control
36
364
400
9.0%
Measures of Association
NNT, OR, RR, HR, RD, AR, p -values
RCT
Lesion at day 6
+
-
+ 376 (30%) 878 1254
Penciclovir
- 526 (41%)
757 1283
Data adapted from K. Kjaerheim et al., 1998
376/1254
OR
(1- 376/1254) 526/1283
376x757 526x878
0.62
(1- 526/1283)
Data adapted from K. Kjaerheim et al., 1998
RCT
Lesion at day 6
+
-
+ 376
878 1254
Penciclovir
- 526
757 1283
Data adapted from K. Kjaerheim et al., 1998
4
Odds ratio = 0.62
The odds for a non-healed lesion at day 6 among individuals on penciclovir is only 62% of that for someone who was on placebo.
% odds decrease = |1 - 0.62| * 100%
The odds for a non-healing lesion among individuals on penciclovier decreased by 38%
The Atlantic 2010
1
SR of RCTs
RCT
All-or-none
SR cohort studies
2
Cohort studies
Ecological studies
3
SR case-control studies Case-control study
Case-reports and case-series
Expert opinion, Biological plausibility, Animal evidence, Bench research
5
Effect size & 95% confidence interval Vertical "no-effect" line
Effect size & 95% confidence interval Vertical "no-effect" line
Effect size & 95% confidence interval Vertical "no-effect" line
Study ID
0.09Fdaily Driscoll (1982) Heifetz (1981) Ringelberg (1982) Subtotal (I-squared = 22.1%, p = 0.277) . 0.09Fweekly Driscoll (1982) Heifetz (1981) Craig (1981) Ringelberg (1982) Horowitz (1971) Chikte (1996) Subtotal (I-squared = 0.0%, p = 0.622) . 0.09Fbiweekly Torell (1965) Poulsen (1983) Subtotal (I-squared = 90.7%, p = 0.001) . Overall (I-squared = 57.6%, p = 0.009)
NOTE: Weights are from random effects analysis
ES (95% CI)
% Weight
21.43 (-1.40, 44.26) 40.69 (23.39, 57.98) 22.75 (3.79, 41.72) 29.54 (16.81, 42.26)
7.93 10.27 9.50 27.70
36.61 (16.02, 57.20) 30.64 (12.12, 49.15) 30.77 (-6.52, 68.06) 20.36 (0.60, 40.12) 35.92 (19.13, 52.72) 15.34 (-6.09, 36.78) 28.77 (20.40, 37.14)
8.81 9.70 4.19 9.16 10.51 8.47 50.84
49.10 (39.83, 58.38) 4.37 (-20.71, 29.45) 28.32 (-15.41, 72.04)
14.32 7.14 21.46
29.81 (21.01, 38.60) 100.00
A Systematic Review of Class IIs and Herbst Appliances -
AUTHORS' CONCLUSIONS: It is not possible to provide any evidencebased guidance to recommend or discourage any type of orthodontic treatment to correct Class II division 2 malocclusion in children.
Cochrane Database Syst Rev. 2006
6
"Caries of teeth is restricted to people and animals who eat liberally of carbohydrate containing foods. Carnivorous man and animals do not suffer from this disease"
McCollum, 1941
1
SR of RCTs
RCT
All-or-none
SR cohort studies
2
Cohort studies
Ecological studies
3
SR case-control studies Case-control study
Case-reports and case-series
Expert opinion, Biological plausibility, Animal evidence, Bench research
What is "normal" Blood Pressure
? Blood pressure history
? Age 55 : 169/98 ? Age 59: 188/105 ? Age 63: 226/118
? Physician assessment:
"no more than normal for a man his age"
New England Journal of Medecine 1995 (332): 1038-1039
7
CHD and Lipids, October 1966
? Framingham
? 2022 males ? 1689 females
? Livermore
? 1961 males
Gofman et al., Circulation, 1966; 679
Cohort Study Smoking/Oral Cancer
? Follow-up a cohort of 10960 individuals; 8857 smokers, 2103 nonsmokers
? Enumerate the number of smokers and nonsmokers that develop oral cancer during a 20 year period
? Tabulate the data in a 2x2 table
Ischemic Heart Disease, Atherosclerosis, and Longevity
Parameters
Incident Heart Disease
Systolic blood pressure Sign. Elevated
Diastolic blood pressure Sign. Elevated
Weight
Sign. Elevated
Cohort Study
Oral carcinoma
+
-
+ 56 (0.6%) 8801
Smoking
- 4 (0.2%) 2099
8857 2103
Data adapted from K. Kjaerheim et al., 1998
56/8857
OR
(1- 56/8857) 4/2103
56x2099 4x8801
3.3
(1- 4/1203)
Data adapted from K. Kjaerheim et al., 1998
Cohort Study
Oral carcinoma
+
-
+ 56
8801
8857
Smoking
-4
2099 2103
Data adapted from K. Kjaerheim et al., 1998
8
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