By I. Ressel. Medical College of Wisconsin.

Appendix 1 lists som e sim pler checklists which I have derived from the users’ guides and the other sources cited at the end of this chapter 20mg tadacip amex, together with som e ideas of m y own discount tadacip 20 mg line. If you are an experienced journal reader order tadacip 20 mg with mastercard, these checklists will be largely self explanatory tadacip 20mg generic. If tadacip 20 mg, however, you still have difficulty getting started when looking at a m edical paper, try asking the prelim inary questions in the next section. The introductory sentence of a research paper should state, in a nutshell, what the background to the research is. For exam ple, "G rom m et insertion is a com m on procedure in children and it has been suggested that not all operations are clinically necessary". This statem ent should be followed by a brief review of the published literature, for exam ple, "G upta and Brown’s prospective 41 H OW TO READ A PAPER survey of grom m et insertions dem onstrated that. It is irritatingly com m on for authors to forget to place their research in context, since the background to the problem is usually clear as daylight to them by the tim e they reach the writing up stage. U nless it has already been covered in the introduction, the m ethods section of the paper should state clearly the hypothesis which the authors have decided to test, such as "This study aim ed to determ ine whether day case hernia surgery was safer and m ore acceptable to patients than the standard inpatient procedure". Again, this im portant step m ay be om itted or, m ore com m only, buried som ewhere m id-paragraph. If the hypothesis is presented in the negative (which it usually is), such as "The addition of m etform in to m axim al dose sulphonylurea therapy will not im prove the control of type 2 diabetes", it is known as a null hypothesis. The authors of a study rarely actually believe their null hypothesis when they em bark on their research. Being hum an, they have usually set out to dem onstrate a difference between the two arm s of their study. But the way scientists do this is to say "Let’s assume there’s no difference; now let’s try to disprove that theory". If you adhere to the teachings of Karl Popper, this hypotheticodeductive approach (setting up falsifiable hypotheses which you then proceed to test) is the very essence of the scientific m ethod. Rem em ber, however, that not all research studies (even good ones) are set up to test a single definitive hypothesis. Qualitative research studies, which are as valid and as necessary as the m ore conventional quantitative studies, aim to look at particular issues in a broad, open-ended way in order to generate (or m odify) hypotheses and prioritise areas to investigate. Even quantitative research (which the rest of this book is about) is now seen as m ore than hypothesis testing. Prim ary studies report research first hand, while secondary 42 G ETTIN G YOU R BEARIN G S (or integrative) studies attem pt to sum m arise and draw conclusions from prim ary studies. Prim ary studies, the stuff of m ost published research in m edical journals, usually fall into one of three categories. The m ore com m on types of clinical trials and surveys are discussed in the later sections of this chapter. M ake sure you understand any jargon used in describing the study design (see Box 3. Secondary research is com posed of: • overviews, considered in Chapter 8, which m ay be divided into: (a) (non-systematic) reviews, which sum m arise prim ary studies (b) systematic reviews, which do this according to a rigorous and predefined m ethodology (c) meta-analyses, which integrate the num erical data from m ore than one study • guidelines, considered in Chapter 9, which draw conclusions from prim ary studies about how clinicians should be behaving • decision analyses, which are not discussed in detail in this book but are covered elsewhere;16, 17, 34–36 these use the results of prim ary studies to generate probability trees to be used by both health professionals and patients in m aking choices about clinical m anagem ent or resource allocation • economic analyses, considered in Chapter 10, which use the results of prim ary studies to say whether a particular course of action is a good use of resources. Exam ples of the sorts of questions that can reasonably be answered by different types of prim ary research study are given in 43 H OW TO READ A PAPER Box 3. In this case, results are analysed by com paring groups Paired (or m atched) Subjects receiving different treatm ents are com parison m atched to balance potential confounding variables such as age and sex. Results are analysed in term s of differences between subject pairs W ithin subject Subjects are assessed before and after an com parison intervention and results analysed in term s of within subject changes Single blind Subjects did not know which treatm ent they were receiving D ouble blind N either investigators nor subjects knew who was receiving which treatm ent Crossover Each subject received both the intervention and control treatm ents (in random order) often separated by a washout period of no treatm ent Placebo controlled Control subjects receive a placebo (inactive pill), which should look and taste the sam e as the active pill. Placebo (sham ) operations m ay also be used in trials of surgery Factorial design A study that perm its investigation of the effects (both separately and com bined) of m ore than one independent variable on a given outcom e (for exam ple, a 2 x 2 factorial design tested the effects of placebo, aspirin alone, streptokinase alone or aspirin plus streptokinase in acute heart attack37) 44 G ETTIN G YOU R BEARIN G S the sections which follow. One question which frequently cries out to be asked is this: was a random ised controlled trial (see section 3. Before you jum p to any conclusions, decide what broad field of research the study covers (see Box 3. Then ask whether the right type of study was done to address a question in this field. For m ore help on this task (which som e people find difficult until they have got the hang of it) see the Oxford Centre for EBM website38 or the journal article by the sam e group. Therapy – testing the efficacy of drug treatm ents, surgical • procedures, alternative m ethods of patient education or other interventions.

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Additional investigators identified associations between cervical spine fracture and mechanism of injury (26 discount tadacip 20mg with mastercard,27) buy discount tadacip 20mg on-line, level of consciousness (20 20 mg tadacip with amex,21 discount tadacip 20 mg otc,27) tadacip 20 mg without a prescription, and intoxi- cation (20,28). However, all of these investigations involved small numbers of subjects with fracture and a single or small number of centers. NEXUS Prediction Rule The first major cohort investigation of clinical indicators for cervical spine imaging was the National Emergency X-Radiography Utilization Study (NEXUS) (5,29). This was a large Level I study performed at 23 different emergency departments across the United States. The goal of the NEXUS study was to assess the validity of four predetermined clinical criteria for cervical spine injury (Table 17. These criteria were (1) altered neurologic function, (2) intoxication, (3) midline posterior bony cervical spine tender- ness, and (4) distracting injury. The NEXUS investigators prospectively enrolled over 34,000 patients who underwent radiography of the cervical spine following blunt trauma. Canadian Cervical Spine Prediction Rule A second level I clinical prediction rule, the Canadian C-spine rule for radi- ography (25) was published subsequent to the NEXUS trial, but with a similar objective: to derive a clinical decision rule that is highly sensitive for detecting acute cervical spine injury. The Canadian C-spine rule was a prospective cohort study of 8924 subjects from 10 community and univer- sity hospitals in Canada. Excluded were patients who had neurologic impairment, decreased mental status, or penetrating trauma. Like the NEXUS study, the Canadian C-Spine Study was an observational study performed without informed patient consent. However, patients who were eligible for the study but did not undergo radiography were followed up with a structured telephone interview 14 days following their discharge from the emergency department (ED). Thus, any patients who had not undergone radiography, and who had missed fracture would potentially be discovered during the investigation. The Canadian study investigated the predictive ability of 20 factors, and based on the reliability and pre- dictive properties of these factors, developed a prediction rule consisting of three questions. The Canadian C-spine rule was validated using a prospective cohort study of 8283 patients presenting at the same 10 Canadian community and academic hospitals as the original study (32). Diagnostic performance Potential decrease Test (reference) Sensitivity Specificity in radiography C-spine prediction rules NEXUS (29) 99. It was noted during the course of this study that physicians failed to evaluate neck range of motion, as required by the Canadian C-spine rule, in 10. While virtually all of this group of incompletely evaluated patients underwent cervical spine imaging (98. The data supporting the adoption of one cervical spine prediction rule over the other is limited. Two studies, the validation study for the Canadian C-spine rule and a retrospective analysis of the Canadian C-spine derivation cohort have attempted to compare the NEXUS and Canadian rules (32,33). However, both cohorts excluded those with altered levels of consciousness, effectively eliminating one of the NEXUS criteria. In addi- tion, others have voiced concerns regarding physician familiarity with the various rules, side-by-side comparison, and the definitions of the NEXUS criteria used in these trials (34,35). The choice of clinical prediction rule in a broader clinical context is also unclear, as no trial has examined the impact of implementing these prediction rules outside of the research setting. Applicability to Children Evidence for who should undergo imaging is less complete in children than in adults. Determination of clinical predictors of injury in pediatric patients is complicated by the decreased incidence of injury in children, requiring a larger sample size for adequate study (36,37). In addition, chil- dren may sustain serious cervical cord injuries that are not radiographi- cally apparent (37,38). Among the level I studies, the Canadian clinical prediction rule development study excluded children (31). The NEXUS trial included children, but there were only 30 injuries in patients under age 18, and only four in patients under age 9 (36). Although no pediatric injuries were missed in the NEXUS study, sample size was too small to adequately assess the sensitivity of the prediction rule in this group. Therefore, no adequate evidence exists regarding appropriate criteria for imaging in children. Summary of Evidence: Cervical spine CT is more sensitive than radiogra- phy, and more specific in patients at high risk of fracture. However, cost-effectiveness analysis demon- strates that CT is cost-effective, and may actually be cost-saving from the societal perspective in patients at high probability of fracture.

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