The Impact Factor (IF): What Is It Good For?

Richard M. Rocco, PhDOctober 2013

1

A Student Challenge

• Find a clinical trial article in the medical literature on a drug or treatment protocol.

• Use that article for a class presentation or term paper.

• Blow the professor away, get an A.

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The Problem

• Where to find the best article. • Stack the odds in your favor with a high level

clinical trial article. • You have a better chance of getting to Chicago

in a 2013 Lexus rather than a broken down 1983 Honda Civic with a bad transmission.

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Hylauronic Acid Intra-articular Injections

• A few weeks ago some students were looking for a clinical trial article on hylauronic injections for a presentation.

• Finding articles on this subject is easy. Finding a high level article is a major challenge.

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Google, 215 000 hits

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Google Scholar, 11 800 hits

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PubMed, 563

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PubMed Clinical Trials, 188

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New England J Medicine, 11 hits

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How to Judge A High Level Clinical Trail

• Was power analysis used?• How were random and systematic errors

controlled for?• What was the stopping rule?• Was the odds ratio converted to risk?• What is the width of the confidence interval?• Was the follow-up sufficiently complete?• What was the likelihood ratio at 95% CI?

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Impact Factor (IF)

• In this presentation I will propose that the use of the IF in journal selection will increase the odds of obtaining a high level, evidence based clinical trial.

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What is the Impact Factor (IF)?

• A statistical calculation introduced by Eugene Garfield at the Institute for Scientific Information (Thomson Reuters) in 1975.

• Impact factors range from 0 to over 50. • The IF represents the number of times in a

journal that an article is cited by other articles. • If the article is good, others will use the data

and cite it in their publications.

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What the IF is Not.

• It is a surrogate marker, not a direct marker of journal quality.

• It is only an average measure of citation numbers.

• An IF of 3 means that the average number of citations received per paper published in the last two years in that journal was 3.

• Reviews, letters to the editor and editorials are not included in the calculations.

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IF Ranking 8238 Science JournalsImpact Factor No. Journals % of Total

< 1.0 3260 39.6 %

1.0 – 2.0 2210 26.8 %

2.1 – 5.0 2188 26.5 %

5.1– 10.0 385 4.7 %

10.1 – 20.0 104 1.3 %

20.1 – 30.0 26 0.3 %

30.1 – >50.0 19 0.2 %

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92.5 % of science journals have an IF of less than 5.0

The IF for Nature for 2011.

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NEJM, IF 53

• A clinical trial published in a high IF journal will not guarantee a high level Lexus clinical trial but it will increase the odds greatly.

• A clinical trial published in a high IF journal will increase the odds that the trial will hold up to careful review and that it will contain a minimum of errors.

• The student can then focus on the importance of the clinical trial and not have to work around the weaknesses of the trial. 16

Journal Impact Factors (IF) 2010-2011

• Jorgensen, A., et al. Ann Rheum Dis 69:1097-1102 (2010) IF = 9.1

• Mei-Dan, O., et al., JAPMA 100:93-100 (2010)

IF = 0.5

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Item Mei-Dan (2010) Jorgensen (2010)

Placebo Controlled No Yes, saline injections

Randomized No Yes

Drug 1% sodium hyaluronate 1% sodium hyaluronate

Dose/injection mg 25 mg 20 mg

Frequency/week 1 1

Number of weeks 5 5

Anesthesia 1% Lidocaine 1% Lidocaine 0.5 mL

Duration of study, weeks 32 52

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Item Mei-Dan (2010) Jorgensen (2010)

# PatientsPower Analysis

15No

335Yes, 151/groupDrug 165, placebo, 170

Informed Consent yes yes

Blinded no yes, double blinded

Age Range, years 20-80 50-72

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Item Mei-Dan (2010) Jorgensen (2010)

Exclusion criteria well defined

Yes Yes

ADR reported No Yes

Treatment Compliance Not given Drug 99%, Placebo 95%

Synovial fluid aspir. No Yes, to prevent drug dilution

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Item Mei-Dan (2010) Jorgensen (2010)

Follow-Up, weeks 32 52

Analgesics used during study

All allowed, pill count not recorded.

All drugs discontinued except for acetaminophen, pills counted.

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Item Mei-Dan (2010) Jorgensen (2010)

Main Outcome Measure Visual Analog Scale Questionnaire

Lequesne Algofunctional Index Score (LFI).

# Questions 6 11 questions

Score 0-10 0-24

Questionnaire administered weeks.

4,8,11,17, 32 4,8,11,17,32

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Item Mei-Dan (2010) Jorgensen (2010)

RESULTS: Visual Analog Scale Day 0 5.29Day 32 3.05 p< 0.001

All data mean, no SD given

Responder RatesHyal 67.9%Placebo 72.4%

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Results

• Mei-Dan, O. (2010)13 of 15 patients improvedimprovement by 20% in range of motion significant reduction in pain using the

visual analog scalehyaluronate is a valid conservative

treatment for…osteoarthritis

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Results

• Jorgensen, A. et al. (2010)time to recurrence showed no significant

treatment effect (p = 0.26)change from baseline pain showed no

treatment effectacetaminophen consumption, global

assessment, responder rates and adverse events, no significant

differencehyaluronan is without clinical effect

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