Interpeting the medical literature book reivew

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Medical Literature 
Interpreting the Medical Literature 

by Stephen H. Gehlbach, 5th ed, 293 pp, with illus, paper, $34.95, ISBN
0-07-143789-4, New York, NY, McGraw-Hill Medical Publishing, 2006. 

JAMA. 2006;296:1410-1411. 

Interpreting the Medical Literature guides us in trying to comprehend
scholarly medical publications. Journal articles have enormous potential
to inform but also to obfuscate. Gehlbach has long been teaching us how
to detect bias, confounding, and flawed analysis.1
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-1
#REF-JBK60120-1>  The past editions of his book were meant "not to daunt
tentative and curious readers but to escort them."2
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-2
#REF-JBK60120-2>  The new fifth edition augments the value of its
predecessors by adding examples from recently published journal articles
and replacing some earlier discussions. In fact, there are fewer pages,
a trend-bucking move for new editions of long-established works. 

During the past decade, readers have learned the principles of
evidence-based medicine (EBM) thanks to the valuable teachings of
Sackett,3
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-3
#REF-JBK60120-3>  Guyatt and Rennie,4
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-4
#REF-JBK60120-4>  and Jenicek.5
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-5
#REF-JBK60120-5>  These authors have variously emphasized evidence
collection, article evaluation, and logical fallacies. The superb detail
of their books, however, could daunt the willing but tentative initiate,
for whom Gehlbach's would instead be an ideal starting point. 

Among the partitions of scientific medical articles, the methods section
plays a vital role. Analysis of generated data and interpretive
discussion of the findings are equally critical aspects. Familiarity
with the underpinning concepts, although often assumed, is not the same
as a firm understanding of the fundamentals. In this area Gehlbach's
book excels over other currently available texts dealing with clinical
epidemiology or EBM.3
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-3
#REF-JBK60120-3> -5
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-5
#REF-JBK60120-5>  

Gehlbach begins with chapters detailing study designs: prospective,
retrospective, and experimental. He stresses the merits of each
depending on the type of inquiry one launches, availability of subjects,
funds, patience, and political will. He proceeds to a painless
evaluation of statistical methods and their shortcomings. Sections
detailing reliability, validity, correlation, diagnostic test
performance, and evaluations of treatment and harm follow. Reviews,
meta-analyses, reflections, and advice conclude the work. 

The volume's strength is the inclusion and discussion of abundant
examples from published works that have appeared in major journals, from
the 1950s through 2005. Postmenopausal hormone therapy, clinical metrics
to predict postmenopausal osteoporosis, sepsis in children, benefits of
exercise, risks from cyclooxygenase 2 inhibitors, the cost of universal
meningococcal vaccines, and many more are foci of discussion. We learn
in elegant and clear language the merits and flaws of each study
design-eg, prospective, experimental, retrospective case-control-subject
and control selection, data analysis, and authors' interpretations of
findings. Praise is prominent, and criticism, where due, is piquant. 

Gehlbach's forte is his ability to dissect effectively major published
articles dealing with common topics. He distills the original data,
analyzes strengths and faults, and reduces the authors' message to
universally understandable denominators. For instance, intake of  
-tocopherol but not  -carotene reduces angina, reaching a significant P
value; however, the low magnitude of this effect, less than 2 in 1000
cases per year, is of arguable clinical significance. Olestra intake,
contrary to initial impressions, seems no more conducive to
gastrointestinal adverse effects than dietary triglycerides when study
participants are ingeniously blinded. Numerous similar, important
research findings come under explicative scrutiny. Cardiac deaths are
lower among pet owners, calling for "perhaps prescriptions for beagles
rather than beta blockers." What is the reason for this observed
reduction in mortality? Is it the pets themselves or the personality
predisposing to pet ownership? Such confounders ("the epidemiologist's
eternal triangle") are explored with humor. The mantric aura around null
hypotheses is dispelled using a judicial analogy (assume "innocence
until guilt is proven" when considering intervention) and illustrative
examples. Greenhalgh's How to Read a Paper is another source that
approaches the art of reading and interpretation in a similar vein.6
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-6
#REF-JBK60120-6>  

Gehlbach's teaching and writing are skillful. When I find a topic
particularly ponderous as covered in other standard works on clinical
epidemiology, I often reach for Gehlbach's clarification. Thus, his book
leaves one hankering for discussions of certain topics that are missing.
These include Bayesian analysis, noninferiority study designs,7
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-7
#REF-JBK60120-7>  the STARD (Standards for Reporting of Diagnostic
Accuracy) initiative,8
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-8
#REF-JBK60120-8>  and the controversial journal impact factor.9
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-9
#REF-JBK60120-9> -10
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-1
0#REF-JBK60120-10>  (He does discuss CONSORT [Consolidated Standards for
Reporting of Trials],11
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#REF-JBK60120-1
1#REF-JBK60120-11>  the other standard for improving the quality of
reports of randomized controlled trials.) Perhaps Gehlbach might tackle
these subjects in future editions. 

Interpreting the Medical Literature is about understanding the
methodology and logic of scientific inquiry. It teaches interpretational
skills needed for understanding medical articles. It has a long and
deserving tradition of clarity in discussing research designs. Its
inimitable merit is the inclusion and analysis of illustrative examples
from major published articles. It is light on jargon, sparing in
statistical complexity, and solid in emphasis of the fundamentals.
Anyone with trepidations about the complexities of epidemiology and EBM
must reach for this gentle book for an auspicious start. 

Financial Disclosures: None reported. 

Saty Satya-Murti, MD, Reviewer 
Robert J. Dole Medical Center 
Wichita, Kan 
University of Kansas Medical Center 
Kansas City 
smurti at cox.net <mailto:smurti at cox.net>  

REFERENCES 

1.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
1#RREF-JBK60120-1>  Gehlbach SH. Interpreting the Medical Literature.
4th ed. New York, NY: McGraw-Hill Medical Publishing Division; 2002. 

2.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
2#RREF-JBK60120-2>  Satya-Murti S, reviewer. Review of: Gehlbach SH.
Interpreting the Medical Literature. 4th ed. JAMA. 2002;288:3169. FREE
FULL TEXT
<http://jama.ama-assn.org/cgi/ijlink?linkType=FULL&journalCode=jama&resi
d=288/24/3169>  

3.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
3#RREF-JBK60120-3>  Sackett DL. Evidence-Based Medicine: How to Practice
and Teach EBM. 2nd ed. New York, NY: Churchill Livingstone; 2000. 

4.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
4#RREF-JBK60120-4>  Guyatt G, Rennie D. Users' Guides to the Medical
Literature: A Manual for Evidence-Based Clinical Practice. Chicago, Ill:
AMA Press; 2002. 

5.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
5#RREF-JBK60120-5>  Jenicek M. Foundations of Evidence-Based Medicine.
New York, NY: Parthenon Publishing Group; 2002. 

6.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
6#RREF-JBK60120-6>  Greenhalgh T. How to Read a Paper: The Basics of
Evidence-based Medicine. 3rd ed. Malden, Mass: BMJ Books; 2006. 
http://bmj.bmjjournals.com/collections/read.shtml. Accessed June 15,
2006. 

7.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
7#RREF-JBK60120-7>  Piaggio G, Elbourne DR, Altman DG, Pocock SJ, Evans
SJ. Reporting of noninferiority and equivalence randomized trials: an
extension of the CONSORT statement. JAMA. 2006;295:1152-1160. FREE FULL
TEXT
<http://jama.ama-assn.org/cgi/ijlink?linkType=ABST&journalCode=jama&resi
d=295/10/1152>  

8.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
8#RREF-JBK60120-8>  Rennie D. Improving reports of studies of diagnostic
tests: the STARD initiative. JAMA. 2003;289:89-90. FREE FULL TEXT
<http://jama.ama-assn.org/cgi/ijlink?linkType=FULL&journalCode=jama&resi
d=289/1/89>  

9.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
9#RREF-JBK60120-9>  Garfield E. The history and meaning of the journal
impact factor. JAMA. 2006;295:90-93. FREE FULL TEXT
<http://jama.ama-assn.org/cgi/ijlink?linkType=FULL&journalCode=jama&resi
d=295/1/90>  

10.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
10#RREF-JBK60120-10>  The PLoS Medicine Editors. The impact factor game:
it is time to find a way to assess the scientific literature. PLoS Med.
doi:10.1371/journal.pmed.0030291. Accessed June 17, 2006. 2006;3:e291. 
FULL TEXT
<http://jama.ama-assn.org/cgi/external_ref?access_num=10.1371/journal.pm
ed.0030291&link_type=DOI>  | PUBMED
<http://jama.ama-assn.org/cgi/external_ref?access_num=16749869&link_type
=MED>  

11.
<http://jama.ama-assn.org/cgi/content/full/296/11/1410?ct#RREF-JBK60120-
11#RREF-JBK60120-11>  CONSORT. The CONSORT statement. 
http://www.consort-statement.org. Accessibility verified June 27, 2006. 

Book and Media Reviews Section Editor: Harriet S. Meyer, MD,
Contributing Editor, JAMA. 

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