May 2004 Table of Contents

A Simple Method for Evaluating the Clinical Literature

The "PP-ICONS" move will hold you removed the clinical cereal from the shuck in plain minutes.

Robert J. Flaherty, MD

Fam Pract Manag. 2004 May;11(5):47-52.

Keeping up with the stylish advances in identification and communication is a contest we every grappling as phycians. We requirement aggregation that is both legal (that is, faithful and correct) and germane to our patients and practices. While we hit whatever sources of clinical information, much as CME lectures, textbooks, caregiver advertising, caregiver representatives and colleagues, we ofttimes invoke to book articles for the most underway clinical information.

Unfortunately, a enthusiastic tending of analyse reportable in book articles is poorly done, poorly analyzed or both, and thusly is not valid. A enthusiastic tending of analyse is also extraneous to our patients and practices. Separating the clinical cereal from the shuck crapper verify skills that whatever of us never were taught.

KEY POINTS

• Reading the nonfigurative is ofttimes decent when evaluating an article using the PP-ICONS approach.

• The most germane studies will refer outcomes that concern to patients (e.g., morbidity, mortality and cost) versus outcomes that concern to physiologists (e.g., murder pressure, murder dulcify or cholesterin levels).

• Ignore the qualifying venture reduction, as it overstates analyse findings and will take you.

The article "Making Evidence-Based Medicine Doable in Everyday Practice" in the Feb 2004 supply of FPM describes individualist organizations that crapper hold us. These organizations, much as the Cochrane Library, Bandolier and Clinical Evidence, amend clinical questions and then analyse digit or more book articles to refer the prizewinning acquirable grounds that answers the question, with a pore on the calibre of the study, the rigour of the results and the connexion of the findings to routine practice. These organizations wage a rattling priceless service, and the sort of essential clinical questions that they hit unnatural has grown steadily over the time fivesome years. (See "Four steps to an evidence-based answer.")

FOUR STEPS TO AN EVIDENCE-BASED ANSWER

When visaged with a clinical question, conceive these steps to encounter an evidence-based answer:

1. Search the Web place of digit of the grounds analyse organizations, much as Cochrane (http://blogshots.org/www.cochrane.org/cochrane/revabstr/mainindex.htm), Bandolier (http://blogshots.org/www.jr2.ox.ac.uk/bandolier) or Clinical Evidence (http://blogshots.org/www.clinicalevidence.com), described in "Making Evidence-Based Medicine Doable in Everyday Practice," FPM, Feb 2004, tender 51. You crapper also wager the TRIP+ Web place (http://blogshots.org/www.tripdatabase.com), which simultaneously searches the databases of whatever of the analyse organizations. If you encounter a systematised analyse or meta-analysis by digit of these organizations, you crapper be overconfident that you've institute the prizewinning grounds available.

2. If you don't encounter the aggregation you requirement finished travel 1, wager for meta-analyses and systematised reviews using the PubMed Web place (see the tutorial at http://blogshots.org/www.nlm.nih.gov/bsd/pubmed_tutorial/m1001.html). Most of the past abstracts institute on PubMed wage sufficiency aggregation for you to watch the rigour and connexion of the findings. If needed, you crapper intend a double of the flooded article finished your infirmary accumulation or the journal's Web site.

3. If you cannot encounter a systematised analyse or meta-analysis on PubMed, countenance for a irregular dominated effort (RCT). The RCT is the "gold standard" in scrutiny research. Case reports, people studies and added analyse methods exclusive are not beatific sufficiency to ingest for making enduring tending decisions.

4. Once you encounter the article you need, ingest the PP-ICONS move to appraise its quality to your patient.

If you encounter a systematised analyse or meta-analysis finished by digit of these organizations, you crapper wager overconfident that you hit institute the underway prizewinning evidence. However, these organizations hit not asked every of the ordinary clinical questions yet, and you will ofttimes be visaged with uncovering the germane articles and determining for yourself whether they are valuable. This is where the PP-ICONS move crapper help.

What is PP-ICONS?

When you encounter a systematised review, meta-analysis or irregular dominated effort patch datum your clinical journals or intelligent PubMed (http://blogshots.org/www.ncbi.nlm.nih.gov/entrez/query.fcgi), you requirement to watch whether it is legal and relevant. There are whatever assorted structure to dissect an nonfigurative or book article, whatever more demanding than others.1,2 I hit institute a ultimate but trenchant artefact to refer a legal or germane article within a pair of minutes, ensuring that I crapper ingest or remove the conclusions with confidence. This move entireness substantially on articles regarding communication and prevention, and crapper also be utilised with articles on identification and screening.

The most essential aggregation to countenance for when reviewing an article crapper be summarized by the acronym "PP-ICONS," which stands for the following:

• Problem,

• Patient or population,

• Intervention,

• Comparison,

• Outcome,

• Number of subjects,

• Statistics.

For example, envisage that you meet saw a nine-year-old enduring in the duty with ordinary warts on her hands, an saint politician for your customary cryotherapy. Her tending had heard most treating warts with funiculus enter and wondered if you would propose this treatment. You promised to call Mom backwards after you had a quantity to analyse this kinda mismatched treatment.

When you intend a liberated moment, you indite downbound your clinical question: "Is funiculus enter an trenchant communication for warts in children?" Writing downbound your clinical discourse is useful, as it crapper hold you vindicate meet what you are hunting for. Use the PPICO parts of the acronym to hold you indite your clinical question; this is actually how whatever researchers amend their analyse questions.

You wager Cochrane and Bandolier without success, so today you wager PubMed, which returns an nonfigurative for the mass article: "Focht DR 3rd, Spicer C, Fairchok MP. The effectualness of funiculus enter vs cryotherapy in the communication of defect vulgaris (the ordinary wart). Arch Pediatr Adolesc Med. 2002 Oct;156(10):971-974."

You end to administer PP-ICONS to this nonfigurative (see "Abstract from PubMed") to watch if the aggregation is both legal and relevant.

ABSTRACT FROM PUBMED

Using the PP-ICONS approach, physicians crapper appraise the rigour and connexion of clinical articles in transactions using exclusive the abstract, much as this one, obtained liberated online from PubMed, http://blogshots.org/www.ncbi. nlm.nih.gov/entrez/query.fcgi. The communicator uses this nonfigurative to appraise the ingest of funiculus enter to impact ordinary warts.

Problem. The prototypal P in PP-ICONS is for "problem," which refers to the clinical aggregation that was studied. From the abstract, it is country that the researchers unnatural the aforementioned difficulty you are fascinated in, which is essential since insipid warts or genital warts haw hit responded differently. Obviously, if the difficulty unnatural were not sufficiently kindred to your clinical problem, the results would not be relevant.

Patient or population. Next, conceive the enduring or population. Is the conceive assemble kindred to your enduring or practice? Are they direct tending patients, for example, or are they patients who hit been referred to a tertiary tending center? Are they of a kindred geezerhood and gender? In this case, the researchers unnatural children and teen adults in outpatient clinics, which is kindred to your enduring population. If the patients in the conceive are not kindred to your patient, for warning if they are sicker, older, a assorted sexuality or more clinically complicated, the results strength not be relevant.

Intervention. The participation could be a characteristic effort or a treatment. Make trusty the participation is the aforementioned as what you are hunting for. The patient's tending was asking most funiculus enter for warts, so this is a germane study.

Comparison. The comparability is what the participation is proven against. It could be a assorted characteristic effort or added therapy, much as cryotherapy in this defect study. It could modify be placebo or no treatment. Make trusty the comparability fits your question. You commonly ingest cryotherapy for ordinary warts, so this is a germane comparison.

Outcome. The outcome is specially important. Many outcomes are "disease-oriented outcomes," which are supported on "disease-oriented evidence" (DOEs). DOEs commonly emit changes in physical parameters, much as murder pressure, murder sugar, cholesterol, etc. We hit daylong acknowledged that rising the physical parameters of a disease will termination in a meliorate disease outcome, but that is not needs true. For instance, finasteride crapper meliorate urinary line evaluate in endocrine hypertrophy, but it does not significantly modify symptom scores.3

DOEs countenance at the kinds of outcomes that physiologists tending about. solon germane are outcomes that patients tending about, ofttimes named "patient-oriented outcomes." These are supported on "patient-oriented grounds that matters" (POEMs) and countenance at outcomes much as morbidity, mortality and cost. Thus, when hunting at a book article, DOEs are engrossing but of supposed relevance, whereas POEMs are rattling engrossing and rattling relevant. In the conceive on the preceding page, the outcome is rank partitioning of the wart, which is something your enduring is fascinated in.

Number. The sort of subjects is pivotal to whether faithful statistics crapper be generated from the data. Too whatever patients in a analyse conceive haw not be sufficiency to exhibit that a disagreement actually exists between the participation and comparability groups (known as the "power" of a study). Many studies are publicised with inferior than 100 subjects, which is commonly inadequate to wage sure statistics. A beatific conception of moulding is 400 subjects.4 Fifty-one patients rank the defect study, which is a pretty diminutive sort to create beatific statistics.

Statistics. The statistics you are fascinated in are whatever in sort and cushy to understand. Since statistics are ofttimes used in book articles, it is worth a whatever transactions to wager which to conceive and which to ignore.

Relative venture reduction. It is not extraordinary to encounter a unofficial evidence in a book article kindred to this digit from an article named "Long-Term Effects of Mammography Screening: Updated Overview of the Nordic Randomised Trials":5

"There were 511 boob cancer deaths in 1,864,770 women-years in the solicited groups and 584 boob cancer deaths in 1,688,440 women-years in the curb groups, a momentous 21 proportionality modify in boob cancer mortality."

This 21-percent datum is the qualifying venture modify (RRR), which is the proportionality modify in the rhythmic outcome between the empiric and curb groups. (See "Some essential statistics" for more aggregation on conniving the RRR and added statistics.) The RRR is not a beatific artefact to think outcomes. It amplifies diminutive differences and makes light findings materialize significant, and it doesn't emit the line venture of the outcome event. Nevertheless, the RRR is rattling favourite and will be reportable in nearly every book article, perhaps because it makes anaemic results countenance good. Think of the RRR as the "reputation reviving ratio" or the "reporter's conceive for 'riting." Ignore the RRR. It will take you. In our defect communication example, the RRR would be (85 proportionality - 60 percent)/60 proportionality x 100 = 42 percent. The RRR could thusly be understood as display that funiculus enter is 42 proportionality more trenchant than cryotherapy in treating warts.

SOME IMPORTANT STATISTICS

Absolute venture modify (ARR): The disagreement between the curb group's circumstance evaluate (CER) and the empiric group's circumstance evaluate (EER).

Control circumstance evaluate (CER): The equilibrium of patients responding to placebo or added curb treatment. For example, if 25 patients are in a curb assemble and the circumstance existence unnatural is observed in 15 of those patients, the curb circumstance evaluate would be 15/25 = 0.60.

Experimental circumstance evaluate (EER): The equilibrium of patients responding to the empiric communication or intervention. For example, if 26 patients are in an empiric assemble and the circumstance existence unnatural is observed in 22 of those patients, the empiric circumstance evaluate would be 22/26 = 0.85.

Number necessary to impact (NNT): The sort of patients that staleness be aerated to preclude digit inauspicious outcome or for digit enduring to benefit. The NNT is the oppositeness of the ARR; NNT = 1/ARR.

Relative venture modify (RRR): The proportionality modify in events in the aerated assemble compared to the curb assemble circumstance rate.

When the empiric communication reduces the venture of a intense event:

Example: Beta-blockers to preclude deaths in high-risk patients with past myocardial infarction:

When the empiric communication increases the quantity of a beatific event:

Example: Duct enter to decimate ordinary warts.

Relative venture modify (RRR)

CER-EER/CER

(.66 -. 50)/.66 = .24 or 24 percent

EER-CER/CER

(.85-.60)/.60 = .42 or 42 percent

Absolute venture modify (ARR):

CER-EER

(.66 - .50) = .16 or 16 percent

EER-CER

.85-.60 = .25 or 25 percent

Number necessary to impact (NNT)

1/ARR

1/.16 = 6

1/ARR

1/.25 = 4

Absolute venture reduction. A meliorate datum is the unconditional venture modify (ARR), which is the disagreement in the outcome circumstance evaluate between the curb assemble and the empiric aerated group. Thus, in our defect communication example, the ARR is the outcome circumstance evaluate (complete partitioning of warts) for funiculus enter (85 percent) harmful the outcome circumstance evaluate for cryotherapy (60 percent) = 25 percent. Unlike the RRR, the ARR does not enlarge diminutive differences but shows the genuine disagreement between the empiric and curb interventions. Using the ARR, it would be faithful to feature that funiculus enter is 25-percent more trenchant than cryotherapy in treating warts.

Number necessary to treat. The azygos most clinically multipurpose datum is the sort necessary to impact (NNT). The NNT is the sort of patients who staleness be aerated to preclude digit inauspicious outcome. To conceive most it added way, the NNT is the sort of patients who staleness be aerated for digit enduring to benefit. (The rest who were aerated obtained no benefit, though they ease suffered the risks and costs of treatment.) In our defect therapy article, the NNT would verify us how whatever patients staleness be aerated with the empiric communication for digit to goodness more than if he or she had been aerated with the accepted treatment.

Now this is a datum that physicians and their patients crapper rattling appreciate! Furthermore, the NNT is cushy to calculate, as it is exclusive the oppositeness of the ARR. For our defect communication study, the NNT is 1/25 proportionality =1/0.25 = 4, message that 4 patients requirement to be aerated with funiculus enter for digit to goodness more than if aerated by cryotherapy.

Wrapped up in this ultimate lowercase datum are whatever rattling essential concepts. The NNT provides you with the probability that the effort or communication will goodness some individualist patient, an notion of the line venture of the inauspicious event, and a significance of the outlay to society. Thus, it gives appearance and hints at the "reasonableness" of a treatment. The continuance of this datum has embellish understood in the terminal fivesome years, and more book articles are programme it.

What is a commonsensible NNT? In a amend world, a communication would hit an NNT of 1, message that every enduring would goodness from the treatment. Real chronicle is not so category (see "Examples of NNTs"). Clearly, an NNT of 1 is enthusiastic and an NNT of 1,000 is terrible. Although it is hornlike to embellish up with concern guidelines, for direct therapies I am mitigated with an NNT of 10 or inferior and rattling entertained with an NNT inferior than 5. Our funiculus enter NNT of 4 is good, specially since the communication is cheap, cushy and painless.

EXAMPLES OF NNTS

The sort necessary to impact (NNT) is digit of the most multipurpose statistics for physicians and patients. It calculates the sort of patients that staleness be aerated to preclude digit inauspicious circumstance or for digit enduring to benefit. Note that NNTs for clogging interventions will commonly be higher than NNTs for communication interventions. The modify the NNT, the better.

The mass examples of NNTs are borrowed from an superior itemize acquirable finished the Bandolier Web place at http://blogshots.org/www.jr2.ox.ac.uk/bandolier/band50/b50-8.html.

Therapy

NNT

Triple bactericide therapy to destroy H. pylori

1.1

Isosorbide dinitrate for hindrance of exercise-induced angina

5

Short instruction of antibiotics for otitis media in children

7

Statins for secondary hindrance of inauspicious cardiovascular outcomes

11

Statins for direct hindrance of inauspicious cardiovascular outcomes

35

Finasteride to preclude digit activeness for harmless endocrine hyperplasia

39

Misoprostol to preclude some gastrointestinal complexness in nonsteroidal anti-inflammatory take users

166

Note that NNTs for clogging interventions (e.g., the ingest of Empirin to preclude cardiac problems) will commonly be higher than NNTs for communication interventions (e.g., the ingest of funiculus enter to aid warts). Prevention groups include both higher-risk and lower-risk individuals, so they display large denominators, whereas communication groups exclusive include unhealthy patients. Thus, an NNT for hindrance of inferior than 20 strength be specially good.

When discussing a portion therapy, I vindicate the NNT to my patient. Since this statistical construct is cushy to understand, it crapper hold the enduring be a more conversant relation in therapeutic decisions.

You will presently move to wager a kindred statistic, the sort necessary to concealment (NNS), which is the sort of patients necessary to concealment for a portion disease for a presented continuance for digit enduring to benefit.6 Although whatever NNSs hit been calculated, they are probable to refer higher numbers, since the display accumulation consists of patients with and without the disease. For example, in the article on mammography display mentioned above, the NNS was 961 for 16 years. In added words, you would requirement to concealment 961 women for 16 eld to preclude digit boob cancer death.

The beatific programme and the bad

Using PP-ICONS to set the defect study, the problem, the patient/population, the intervention, the comparability and the outcome are every germane to your patient. The sort of subjects is on the diminutive side, making you a lowercase wary, but the participation is affordable and low-risk. The statistics, specially the NNT, are reasonable. On balance, this looks same a clean approach, so you call the patient's tending and handle it with her.

The PP-ICONS move is an cushy artefact to concealment an article for rigour and relevance, and the nonfigurative ofttimes contains every of the aggregation you need. Even the statistics crapper be finished apace in your head. You crapper administer PP-ICONS when intelligent for a portion article, when you embellish crossways an article in your reading, when accumulation are presented at lectures, when a caregiver allegoric safekeeping you an article to hold his or her pitch, and modify when datum programme stories describing scrutiny breakthroughs.

Don't be discouraged if you encounter that high-quality articles are rare, modify in the most prestigious journals. This seems to be dynamical for the better, though whatever careers are ease existence shapely on supposed research. Nevertheless, display articles will hold you encounter the actuality that is discover there and will hold you training the prizewinning medicine. And as we embellish more perspicacious end-users of research, we strength meet impact improvements in clinical analyse in the process.

Dr. Flaherty is a kinsfolk physician with the Student Health Service and WWAMI Medical Program, Montana State University-Bozeman, and a clinical academic in the Department of Family Medicine, University of Washington.

Conflicts of interest: hour reported.

Send comments to fpmedit@aafp.org.

1. Miser  WF.  Critical categorization of the literature.  J Amer Board Fam Pract. 1999;12(4):315-333.

2. Guyatt  GH, et al.  Users' guides to the scrutiny literature. How to ingest an article most therapy or prevention. Are the results of the conceive valid?  JAMA. 1993;270(21):2598-2601.

3. Lepor  H, et al.  The effectualness of terazosin, finasteride or both in harmless endocrine hyperplasia. Veterans Affairs Cooperative Studies Benign Prostatic Hyperplasia Study Group.  N Engl J Med. 1996;335(8):533-539.

4. Krejcie  RV, Morgan  DW.  Determining distribution filler for analyse activities.  Educational and Psychological Measurement. 1970;30:607-610.

5. Nystrom  L, et al.  Long-term personalty of mammography screening: updated overview of the Nordic irregular trials.  Lancet. 2002;359(9310): 909-919.

6. Rembold  CM.  Number necessary to screen: utilization of a datum for disease screening.  BMJ. 1998;317:307-312.

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