By F. Ur-Gosh. Life Pacific College.
In interpreting "negative" trials naltrexone 50 mg cheap, one im portant thing you need to know is "would a m uch larger trial be likely to show a significant benefit? N ow ask yourself "W ould this level of difference 89 H OW TO READ A PAPER be clinically significant? If buy naltrexone 50mg, on the other hand 50mg naltrexone, the upper 95% confidence interval represented a clinically significant level of difference between the groups generic naltrexone 50 mg visa, the trial m ay be negative but it is also non-definitive. U ntil recently, the use of confidence intervals was relatively uncom m on in m edical papers. In one survey of 100 articles from three top journals (The New England Journal of Medicine, Annals of Internal Medicine, and Canadian Medical Association Journal), only 43% reported any confidence intervals at all, whereas 66% gave a p value. You should check carefully in the discussion section to see whether the authors have correctly concluded (a) whether and to what extent their trial supported their hypothesis and (b) whether any further studies need to be done. It is all very well to say that a particular intervention produces a "statistically significant difference" in outcom e but if I were being asked to take a new m edicine I would want to know how m uch better m y chances would be (in term s of any particular outcom e) than they would be if I didn’t take it. Four sim ple calculations (and I prom ise you they are sim ple: if you can add, subtract, m ultiply, and divide you will be able to follow this section) will enable you to answer this question objectively and in a way which m eans som ething to the non-statistician. The calculations are the relative risk reduction, the absolute risk reduction, the num ber needed to treat, and the odds ratio. To illustrate these concepts, and to persuade you that you need to know about them , let m e tell you about a survey which Tom Fahey and his colleagues conducted in 1995. Of the 140 board m em bers who responded, only three spotted that all four "program m es" in fact related to the sam e set of results. The other 137 all selected one of the program m es in preference to one of the others, thus revealing (as well as their own ignorance) the need for better basic training in epidem iology for health authority board m em bers. The final way of expressing the effect of treatm ent which I want to introduce here is the odds ratio. The general form ulae for calculating these "bottom line" effects of an intervention are reproduced in Appendix 4 and for a discussion on which of these values is m ost useful in which circum stances, see Jaenschke and colleagues’ article in the "Basic statistics for clinicians" series3 or Chapter 7 (D eciding on the best therapy) of Sackett et al’s clinical epidem iology textbook. Statistics can be an intim idating science and understanding its finer points often calls for expert help. But I hope that this chapter has shown you that the statistics used in m ost m edical research papers can be evaluated by the non-expert using a sim ple checklist such as that in Appendix 1. In addition, you m ight like to check the paper you are reading (or writing) against the com m on errors given in Box 5. Effect of coronary artery bypass surgery on survival: overview of ten year results from random ized trials by the Coronary Artery Surgery Triallists Collaboration. The m ost effective way of changing the prescribing habits of a clinician is via a personal representative (known to m ost of us in the U K as the "drug rep" and to our N orth Am erican colleagues as the "detailer"), who travels round with a briefcase full of "evidence" in support of his or her wares. Com m on (and hopefully trivial) adverse drug reactions m ay be picked up, and their incidence quantified, in the RCTs undertaken to dem onstrate the drug’s efficacy. But rare (and usually m ore serious) adverse drug reactions require both pharm acovigilance surveys (collection of data prospectively on patients receiving a 94 PAPERS TH AT REPORT D RU G TRIALS newly licensed drug) and case-control studies (see section 3. Ideally, individual rechallenge experim ents (where the patient who has had a reaction considered to be caused by the drug is given the drug again in carefully supervised circum stances) should be perform ed to establish causation. Preferably, find a surrogate endpoint that is heavily influenced by the drug, though it m ay not be strictly valid (see section 6. If you m ust com pare it with a com petitor, m ake sure the latter is given at subtherapeutic dose • Include the results of pilot studies in the figures for definitive studies ("Russian doll publication"), so it looks like m ore patients have been random ised than is actually the case • Om it m ention of any trial that had a fatality or serious adverse drug reaction in the treatm ent group. If possible, don’t publish such studies • G et your graphics departm ent to m axim ise the visual im pact of your m essage. It helps not to label the axes of graphs or say whether scales are linear or logarithm ic. M ake sure you do not show individual patient data or confidence intervals • Becom e m aster of the hanging com parative ("better" – but better than what? D r Andrew H erxheim er, who edited Drug and Therapeutics Bulletin for m any years, once undertook a survey of "references" cited in advertisem ents for pharm aceutical products in the leading U K m edical journals.
Plantar Stress Injury Plantarly directed forces may result in sprains to the mid- tarsal region with avulsion fractures of the dorsal lip of the navicular buy discount naltrexone 50 mg online, talus purchase naltrexone 50mg with amex, or anterior process of the calcaneus 50mg naltrexone visa. Crush injuries Navicular Fractures Eichenholtz And Levin Classiﬁcation Type I: Avulsion fractures of tuberosity Type II: A fracture involving the dorsal lip Type III: A fracture through the body Sangeorzan Classiﬁcation (Figure 3 buy cheap naltrexone 50mg line. Sangeorzan BJ, Benirschke SK, Mosca V, Mayo KA, and Hansen ST Jr: Displaced intra-articular fractures of the tarsal navicular. Continued 74 FRACTURE CLASSIFICATIONS IN CLINICAL PRACTICE Type III: Comminuted fracture pattern with naviculo-cuneiform joint disruption; associated fractures may exist (cuboid, anterior calcaneus, calcaneocuboid joints). Cuboid Fractures OTA Classiﬁcation Of Cuboid Fractures Higher letters and numbers denote more signiﬁcant injury. Type A: Extraarticular Type A1: Extraarticular, avulsion Type A2: Extraarticular, coronal Type A3: Extraarticular, multifragmentary Type B: Partial articular, single joint (calcaneocuboid or cubotarsal) Type B1: Partial articular, sagittal Type B2: Partial articular, horizontal Type C: Articular, calcaneocuboid and cubotarsal involvement Type C1: Articular, multifragmentary Type C1. PELVIS AND LOWER LIMB 75 Tarsometatarsal (Lisfranc) Joint Quenu and Kuss Classiﬁcation (Figure 3. Fracture-dislocations of the tarsometatarsal joints: end results correlated with pathology and treatment. Copyright © 1986 by the American Orthopaedic Foot and Ankle Society (AOFAS), originally published in Foot and Ankle Interna- tional, April 1986, Volume 6, Number 5, page 228 and reproduced here with permission. Divergent Partial Total Fractures of the Base of the Fifth Metatarsal Dameron Classiﬁcation (Figures 3. Reprinted from The Journal of the American Academy of Orthopaedic Surgeons, Volume 3 (2), pp. Type II: Transphyseal fracture that exits the metaphysis; the metaphyseal fragment is known as the Thurston- Holland fragment; the periosteal hinge is intact on the side with the metaphyseal fragment; prognosis is excel- lent, although complete or partial growth arrest may occur in displaced fractures. Type III: Transphyseal fracture that exits the epiphysis, causing intraarticular disruption; anatomic reduction and ﬁxation without violating the physis are essential; pro- gnosis is guarded because partial growth arrest and resultant angular deformity are common problems. Type IV: Fracture that traverses the epiphysis and the physis, exiting the metaphysis; anatomic reduction and ﬁxation without violating the physis are essential; pro- gnosis is guarded, because partial growth arrest and resultant angular deformity are common. Type V: Crush injury to the physis; diagnosis is generally made retrospectively; prognosis is poor because growth arrest and partial physeal closure commonly result. It can cause scaring, tethering and arrest of the periphery of the epiphyseal plate, producing angular deformity. SUPRACONDYLAR HUMERUS FRACTURES Classiﬁcation of Extension Type Gartland Classiﬁcation Based on degree of displacement: Type I: Nondisplaced Type II: Displaced with intact posterior cortex; may be slightly angulated or rotated Type III: Complete displacement; Posteromedial or postero- lateral Wilkins Modiﬁcation of Gartland’s Classiﬁcation Type 1: Undisplaced 4. FRACTURES IN CHILDREN 81 Type 2 Type 2A: Intact posterior cortex and angulation only Type 2B: Intact posterior cortex, angulation and rotation Type 3 Type 3A: Completely displaced, no cortical contact, posteromedial Type 3B: Completely displaced, no cortical contact, posterolateral LATERAL CONDYLAR PHYSEAL FRACTURES Milch Classiﬁcation (Figure 4. Type II: Fracture line extends into the apex of the trochlea, rep- resenting a Salter-Harris type II fracture. Group B: Lateral condyle ossiﬁed (7 months to 3 years); Salter- Harris type I or II (ﬂeck of metaphysis). Group C: Large metaphyseal fragment, usually exiting laterally (ages 3 to 7 years). T-CONDYLAR FRACTURES Wilkins and Beaty Classiﬁcation Type I: Nondisplaced or minimally displaced Type II: Displaced, with no metaphyseal comminution Type III: Displaced, with metaphyseal comminution 4. FRACTURES IN CHILDREN 83 RADIAL HEAD AND NECK FRACTURES Wilkins Classiﬁcation (Figure 4. Continued PEDIATRIC FOREARM Descriptive Classiﬁcation Location: Proximal, middle, or distal third Type: Plastic deformation, incomplete ("greenstick"), com- pression ("torus" or "buckle"), or complete displacement angulation Associated physeal injuries: Salter-Harris Types I to V SCAPHOID Classiﬁcation Type A: Fractures of the distal pole Type A1: Extraarticular distal pole fractures Type A2: Intraarticular distal pole fractures Type B: Fractures of the middle third Type C: Fractures of the proximal pole 86 FRACTURE CLASSIFICATIONS IN CLINICAL PRACTICE FIGURE 4. FRACTURES IN CHILDREN 87 TIBIAL SPINE (INTERCONDYLAR EMINENCE) FRACTURES Meyers and McKeever Classiﬁcation (Figure 4. FRACTURES IN CHILDREN 89 CALCANIAL FRACTURES Schmidt and Weiner Classiﬁcation of Calcaneal Fractures Type I: Fracture of the tuberosity of apophyses Type IA: Fracture of the sustentaculum Type IB: Fracture of the anterior process Type IC: Fracture of the anterior inferolateral process Type ID: Avulsion fracture of the body Type II: Fracture of the posterior and/or superior parts of the tuberosity Type III: Fracture of the body not involving the subtalar joint Type IV: Nondisplaced or minimally displaced fracture through the subtalar joint Type V: Displaced fracture through the subtalar joint Type VA: Tongue type Type VB: Joint depression type Type VI: Either unclassiﬁed or serious soft-tissue injury, bone loss, and loss of the insertions of the Achilles tendon Chapter 5 Periprosthetic Fractures PERIPROSTHETIC HIP FRACTURES Vancouver Classiﬁcation (Duncan and Masri) Type A: Involve the trochanteric area (AG involve the greater trochanter, AL involve the lesser trochanter) Type B: Fractures around the stem or extending slightly dis- tal to it (B1 implant well ﬁxed, B2 implant loose, bone stock adequate, B3 implant loose, bone stock inadequate) Type C: Fractures distal to the stem that the presence of the femoral component may be ignored Johansson Classiﬁcation Type I: Fracture proximal to prosthetic tip with the stem remain- ing in the medullary canal Type II: Fracture extending beyond distal stem with dislodge- ment of the stem from the distal canal Type III: Fracture entirely distal to the tip of the prosthesis Cooke And Newman (Modiﬁcation Of Bethea) (Figure 5. Cooke and Newman classiﬁcation of periprosthetic fracture about total hip implants. Reproduced with permission and copyright © of The Journal of Bone and Joint Surgery, Inc.
Do not insult the audience by presenting them with a jumble of slides purchase 50 mg naltrexone amex, sometimes known as "pick-and-mix" slides generic naltrexone 50 mg, which you have obviously used before for many different talks discount 50mg naltrexone visa. Instead of listening to the content of the lecture safe 50 mg naltrexone, the audience will be wondering on whom you last inflicted that dreadful, rainbow-coloured, illegible slide. Never use more than eight lines per slide and if at all possible stop at six lines. If necessary, divide the content between two slides rather than cram in extra lines. It is always preferable to keep to a single line for each point that you are making: you lose impact by using two or, even worse, three lines. Select a clear uncluttered typeface that can be read easily, scan some of the newspapers to gain ideas about those typefaces that can be read best at a distance. Avoid upper case text (capital letters) as this is more difficult to read quickly than lower case text. If you wish to emphasise a point, underline the relevant word; a different typeface occasionally works but can distract from the rest of the slide. If you have to explain the layout of a slide to the audience then you have failed. The same general principles apply to figures as to the text: the colour combinations must be consistent throughout the presentation and it is essential to avoid overcrowding the figures. Because the editor of a journal insisted that you combine four small graphs into a single figure does not mean that you should inflict the same layout on the audience. The decision of the editor was based on the need to save space in the journal; your objective is completely different – that of imparting information with clear, unambiguous slides, so the rule is one graph for one slide. Complicated pie charts often look impressive in publications but are not suitable for slides because it is difficult for the audience to assimilate the information rapidly. It is preferable to use different symbols for different lines on a graph rather than different colours. Although it seems instinctive to consider different colours for different lines, this only works if the lines are well separated. If possible try to give an indication of the variability of the data but look carefully to be certain that this does not make the slide messy and detract from the message. If necessary, you simply tell the audience that the data on the variability of the results are available and that they will have to trust your statistical analysis for the presentation. All labels should be written horizontally, abbreviated if necessary – unless you like inducing neck injuries in the audience – and should be self-explanatory. You undoubtedly remember whom groups 1-4 were, but most of the audience forgot 15 minutes ago, so label them appropriately – for example: sober, mildly drunk, very drunk, and members of college council. Avoid whizzy 3-D options: in most instances they add nothing to the presentation and just tell the audience that you are an anorak who reads the software manual. Alignment of the columns is essential in a table, otherwise the eye is drawn inevitably to the misalignment and obvious kinks. It is almost always true to say that a table prepared for publication is totally unsuitable for presentation as a slide. There is far too much information and most of it will be illegible when viewed from a distance. Check very carefully for mistakes, they occur commonly, and are more likely to be spotted by a colleague who has not seen the material before. Your colleague should sit in the back row of the lecture theatre to ensure that all the information can be seen easily. It is sometimes hard to admit that your favourite slide is less than perfect, but it is important to find out well before the presentation. As you rehearse check that the slides fulfil the basic functions list on page 16 to ensure that they develop a coherent story. There is still the small matter of rehearsal, rehearsal, and, when you think that the talk is polished, even more rehearsal. Summary • Visual aids are essential when giving medical presentations • Only use board and coloured pens if you have the necessary talent; flipcharts are also not encouraged • Videos are occasionally valuable in demonstrating a new practical technique • Slides are the most common form of visual aid used, especially in PowerPoint • Remember that the fewer slides used the better, keep them simple and make figures and tables easy to understand 33 HOW TO PRESENT AT MEETINGS 5 Computer-generated slides: how to make a mess with PowerPoint GAVIN KENNY You have been asked to present the essence of your life’s work to date, to give a description of the last patient you treated who exhibited some rare form of eruption, or to summarise and explain the item which caught your tutor’s eye in the most recent copy of a journal. It is important to remember that if you do not have good data, then your audio-visual aids must be outstanding.
We inquire in order to decide not only what information is relevant purchase naltrexone 50mg on line, but what and how much can or should be called into question at one time generic 50 mg naltrexone otc. Should we evaluate "experimental" or "heroic" new treatments primarily as they affect the lives of the patients treated or in terms of possible future benefits to society? How do we present these considerations to the patients themselves discount 50 mg naltrexone fast delivery, when we know that no presentation can be completely neutral? Were attempts to mechanically ventilate premature babies weighing less than 1 order 50mg naltrexone amex,000 grams, uniformly failures in the 1960’s, justified by the learning which resulted in frequent successes today? What considerations were considered relevant to the rationale for early heart transplants? Exactly how and when is an arduous and painful diagnostic and treatment course justified for any particular person? Are resources spent on major surgery for pets justified when they could be diverted to the care of people? How much does a cultural or psychological attitude toward death influence care at the end of life in any particular case? Should an aged Inuit be subjected to a medical or psychological evaluation if she feels ready to depart into the snow? Descriptions report and narratives explain but there are multiple possible levels and extensions of reporting, and many possible narratives for explaining meaning. One act can be assessed in terms of a narrow or a broad descriptive focus and also can be subsumed under several narratives. Thus the "preventing a lawsuit" narrative and the "making a living" narrative can diverge from the "giving the best care" JOHN DEWEY’S PERSPECTIVES ON MEANS AND ENDS 91 narrative. Recipes for clinical care are supposed to dictate choices when doing so is really helpful, but they always involve assumptions about narrative and descriptive context which need, at the proper time, to be examined. The fact that rigidity and automaticity work sometimes does not mean that they work all the time. Even in the greatest emergencies conditions may arise which demand that we not be creatures of protocol. The two great pitfalls around context which Dewey identifies are failing to consider context and its particularities, so that our actions become inappropriate in the light of it, and discounting central concerns and priorities because considerations are too diffuse. There is a time to discount and ignore and a time to pay attention to some individual fact; a time to accept the obvious and a time to question it. There is a time to concentrate and a time to look around; a time to make a judgment and a time to withhold one. Bayesian reasoning, with its controversial concept of prior probability is one attempt to assess, semi-formally, the importance of context. In a nutshell, it offers a method for weighting the significance of an individual piece of data given certain aspects of the context in which it occurs. Informally, we do this all the time, for example when we decide to double check a laboratory value which makes no sense in light of what we know already about a case. When studies come out "proving" that penicillin does not shorten the course of streptococcal pharyngitis, that antibiotics do not help cat scratch disease, that triglycerides do not affect heart disease, that ibuprofen is as safe as acetaminophen in children over six months and that post-menopausal estrogen causes breast cancer (or does not), that a high fiber diet can (or cannot) prevent colon cancer or that personality does or does not affect heart attack risk, we take all with "a grain of salt. No matter how compelling the statistical evidence internal to one study may be, it does not exist in a contextual vacuum. For example, suppose that a serologic test for HIV is positive in 95% of people actually infected with HIV and in 1% of people who are not infected. When such a test is used in a population "previously known" to have a low incidence of HIV infection, say "worried well college students" who havea1in1,000 chance of being infected, a positive test has much less predictive value than it does in a population of 1,000 prisoners whose "prior probability" of being infected is, say, 10%. When prior probabilities are actually applicable to the group being tested, and in this lies the controversy, the predictive value of the test comes out as follows: For the 1,000 college students 92 CHAPTER 3 there is one who will likely have a true positive test result and there are 10 who will have false positive tests. After the test, the probability of anyone testing positive actually being infected is about. The predictive value of a negative test only improves the odds that one is not infected in this group from. In contrast, for the prisoners, out of the 100 actually infected, 95 will test positive and out of the 900 not infected, 9 will test positive. A test is most useful when it most strongly changes the odds that a disease is present, and that depends on the setting in which it is used.
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