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Data collected retrospectively by reviewing the medical records may have poor data quality buy trihexyphenidyl 2 mg mastercard pain treatment center dr mckellar. The records used to collect data may contain inadequate detail and possess questionable reliability generic 2mg trihexyphenidyl otc treatment for dog neck pain. They may also use varying and sub- jective standards to judge symptoms cheap 2 mg trihexyphenidyl overnight delivery pain treatment endometriosis, signs of disease severity, or outcomes. The implicit review of charts introduces the researcher’s bias in interpreting both measurements and outcomes. If there are no objective and explicit criteria for evaluating the medical records, the infor- mation contained in them is open to misinterpretation from the observer. It has been shown that when performing implicit chart reviews, researchers subcon- sciously fit the response that best matched their hypothesis. Researchers came up with different results if they performed a blinded chart review as opposed to an unblinded review. Explicit reviews are better and can occur when only clearly objective outcome measures are reviewed. Even when the outcomes are more objective it is better to have the chart material reviewed in a blinded manner. The Hawthorne effect was first noticed during a study of work habits of employees in a light bulb factory in Illinois during the 1920s. It occurs because being observed during the process of making measurements changes the behav- ior of the subject. In the physical sciences, this is known as the Heisenberg Uncer- tainty Principle. If subjects change their behavior when being observed, the out- come will be biased. One study was done to see if physicians would prescribe less expensive antibiotics more often than expensive new ones for strep throat. In this case, the physicians knew that they were being studied and in fact, they prescribed many more of the low-price antibiotics during the course of the study. After the study was over, their behavior returned to baseline, thus they acted differently and changed their clinical practices when being observed. This and other observer biases can be prevented through the use of unobtrusive, blinded, or objective measurements. Misclassification bias Misclassification bias occurs when the status of patients or their outcomes is incorrectly classified. If a subject is given an inaccurate diagnosis, they will be counted with the wrong group, and may even be treated inappropriately due to their misclassifaction. For instance, in a study of antibiotic treatment of pneumonia, patients with bronchi- tis were misclassified as having pneumonia. Those patients were more likely to get better with or without antibiotics, making it harder to find a difference in the outcomes of the two treatment groups. Patients may also change their behaviors or risk factors after the initial grouping of subjects, resulting in misclassification bias on the basis of exposure. Misclassification of outcomes in case control studies can result in failure to correctly distinguish cases from controls and lead to a biased conclusion. One must know how accurately the cases and controls are being identified in order to avoid this bias. If the disorder is relatively common, some of the control patients may be affected but not have the symptoms yet. One way of compensating for Sources of bias 87 this bias is to dilute the control group with extra patients. This will reduce the extent to which misclassification of cases incorrectly counted as controls will affect the data. Let’s say that a researcher wanted to find out if people who killed themselves by playing Russian Roulette were more likely to have used alcohol than those who committed suicide by shooting themselves in the head. The researcher would look at death investigations and find those that were classified as suicides and those that were classified as Russian Roulette. However, the researcher suspects that some of the Russian Roulette cases may have been misclassified as suicides to “protect the victim. Obviously if Russian Roulette deaths are routinely misclassified, this strategy will not result in any change in the bias. Outcome classification based upon subjec- tive data including death certificates, is more likely to exhibit this misclassifica- tion. This will most likely result in an outcome that is of smaller size than the actual effect. This bias can be prevented with objective standards for classifica- tion of patients, which should be clearly outlined in the methods section of a study. Miscellaneous sources of bias Confounding Confounding refers to the presence of several variables that could explain the apparent connection between the cause and effect. If a particular variable is present more often in one group of patients than in another, it may be respon- sible for causing a significant effect. For example, a study was done to look for the effect of antioxidant vitamin E intake on the outcome of cardiovascular dis- ease. It turned out that the group with high vitamin E intake also had a lower rate of smoking, a higher socioeconomic status, and higher educational level than the groups with lower vitamin E intake. It is much more likely that those other variables are responsible for all or part of the decrease in observed cases of car- diovascular disease. There are statistical ways of dealing with confounding vari- ables called multivariate analyses. The rules governing the application of these types of analyses are somewhat complex and will be discussed in greater detail in Chapter 14. When looking at studies always look for the potential presence of confounding variables and at least make certain that the authors have adjusted for those variables. However, no matter how well the authors have adjusted, it can be very difficult to completely remove the effects of confounding from a study. Contimination is more commonly seen in randomized clin- ical trials, but can also exist in observational studies. In an observational study, it occurs if the control group is exposed to the same risk factor as the study group. However, there may be an environmental situation by which those classi- fied as not exposed to the risk factor are actually exposed.

Neurological exam A doctor will closely evaluate the person for problems that may signal brain disorders other than Alzheimer’s cheap 2mg trihexyphenidyl mastercard pain management in dogs and cats. The physician will also test: » Reflexes » Coordination » Muscle tone and strength » Eye movement » Speech » Sensation The doctor is looking for signs of small or large strokes trihexyphenidyl 2 mg online pain medication safe dogs, Parkinson’s disease generic 2 mg trihexyphenidyl with mastercard joint and pain treatment center lompoc ca, brain tumors, fluid accumulation on the brain, and other illnesses that may impair memory or thinking. Researchers are studying other imaging techniques so they can better diagnose and track the progress of Alzheimer’s. A diagnosis of Alzheimer’s reflects a doctor’s best judgment about the cause of a person’s symptoms, based on the testing performed. Find out if the doctor will manage care going forward and, if not, who will be the primary doctor. Alzheimer’s disease is life-changing for both the diagnosed individual and those close to him or her. While there is currently no cure, treatments are available that may help relieve some symptoms. Research has shown that taking full advantage of available treatment, care and support options can improve quality of life. A timely diagnosis often allows the person with dementia to participate in this planning. The person can also decide who will make medical and financial decisions on his or her behalf in later stages of the disease. This interactive tool evaluates needs, outlines action steps and links the user to local services and Association programs. Since Alzheimer’s affects people in different ways, each person may experience symptoms — or progress through the stages — differently. On average, a person with Alzheimer’s lives four to eight years after diagnosis, but can live as long as 20 years, depending on other factors. Changes in the brain related to Alzheimer’s begin years before any signs of the disease. The following stages provide an overall idea of how abilities change once symptoms appear and should be used as a general guide. Stages may overlap, making it difficult to place a person with Alzheimer’s in a specific stage. Early-stage Alzheimer’s In the early stage of Alzheimer’s, a person may function independently. Despite this, the person may feel as if he or she is having memory lapses, such as forgetting familiar words or the location of everyday objects. During a detailed medical interview, doctors may be able to detect problems in memory or concentration. As the disease progresses, the person with Alzheimer’s will require a greater level of care. You may notice the person with Alzheimer’s confusing words, getting frustrated or angry, or acting in unexpected ways, such as refusing to bathe. Damage to nerve cells in the brain can make it difficult to express thoughts and perform routine tasks. At this point, symptoms will be noticeable to others and may include: » Forgetfulness of events or about one’s own personal history. People can wander or become confused about their location at any stage of the disease. If not found within 24 hours, up to half of those who get lost risk serious injury or death. Late-stage Alzheimer’s In the final stage of the disease, individuals lose the ability to respond to their environment, carry on a conversation and, eventually, control movement. As memory and cognitive skills worsen, significant personality changes may occur and extensive help with daily activities may be required. At this stage, individuals may: » Need round-the-clock assistance with daily activities and personal care. But drugs and non-drug treatments may help with both cognitive and behavioral symptoms. A comprehensive care plan for Alzheimer’s disease: » Considers appropriate treatment options. By keeping levels of acetylcholine high, these drugs support communication among nerve cells. Three cholinesterase inhibitors are commonly prescribed: » Donepezil (Aricept®), approved in 1996 to treat mild-to-moderate Alzheimer’s and in 2006 for the severe stage. The second type of drug works by regulating the activity of glutamate, a different messenger chemical involved in information processing: » Memantine (Namenda®), approved in 2003 for moderate-to-severe stages, is the only drug in this class currently available. The third type is a combination of cholinesterase inhibitor and a glutamate regulator: » Donepezil and memantine (Namzaric®), approved in 2014 for moderate-to-severe stages. While they may temporarily help symptoms, they do not slow or stop the brain changes that cause Alzheimer’s to become more severe over time. Behavioral symptoms Many find behavioral changes, like anxiety, agitation, aggression and sleep disturbances, to be the most challenging and distressing effect of Alzheimer’s disease. Other possible causes of behavioral symptoms include: » Drug side effects Side effects from prescription medications may be at work. Drug interactions may occur when taking multiple medications for several conditions. There are two types of treatments for behavioral symptoms: non-drug treatments and prescription medications. Non-drug treatments Steps to developing non-drug treatments include: » Identifying the symptom. Often the trigger is a change in the person’s environment, such as: » New caregivers. Because people with Alzheimer’s gradually lose the ability to communicate, it is important to regularly monitor their comfort and anticipate their needs. Prescription medications Medications can be effective in managing some behavioral symptoms, but they must be used carefully and are most effective when combined with non-drug treatments. Medications should target specific symptoms so that response to treatment can be monitored. Use of drugs for behavioral and psychiatric symptoms should be closely supervised. Some medications, called psychotropic medications (antipsychotics, antidepressants, anti-convulsants and others), are associated with an increased risk of serious side effects. These drugs should only be considered when non-pharmacological approaches are unsuccessful in reducing dementia-related behaviors that are causing physical harm to the person with dementia or his or her caregivers.

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The follow-up measurements and determination of the original outcomes are made when the data are finally analyzed at the end of the study purchase 2 mg trihexyphenidyl otc chronic pain treatment guidelines 2013. The data will then be used for another purchase 2mg trihexyphenidyl otc knee pain treatment ligament, later study and analyzed for a new risk factor other than the one for which the original study was done buy 2mg trihexyphenidyl overnight delivery pain and headache treatment center in manhasset ny. For example, a cohort of patients with trauma due to motor- vehicle-accident is collected to look at the relationship of wearing seat belts to death. After the data are collected, the same group of patients is looked at to see if there is any relationship between severe head injury and the wearing of seat belts. In general, for a non-concurrent cohort study, the data are available from databases that have already been set up. The data should be gathered in an objec- tive manner or at least without regard for the association which is being sought. Since non-concurrent cohort studies rely on historical data, they may suffer some of the weaknesses associ- ated with case–control studies regarding recall bias, the lack of uniformity of data recorded in the data base, and subjective interpretation of records. To review Subjects in case–control studies are initially grouped according to the pres- ence or absence of the outcome and the ratio between cases and controls is arbitrary and not reflective of their true ratio in the population. Subjects in cohort studies are initially grouped according to the presence or absence of risk factors regardless of whether the group was assembled in the past or the present. Clinical trials A clinical trial is a cohort study in which the investigator intervenes by manipu- lating the presence or absence of the risk factor, usually a therapeutic maneuver. Tradi- tional cohort and case–control studies are observational studies in which there is no intentional intervention. An example of a clinical trial is a study in which a high-soy-protein diet and a normal diet were given to middle-aged male smok- ers to determine if it reduced their risk of developing diabetes. A cohort study of the same ‘risk factor’ would look at a group of middle-aged male smokers and see which of them ate a high-soy-protein diet and then follow them for a period of time to determine their rates of developing diabetes. Clinical trials are characterized by the presence of a control group identical to the experimental patients in every way except for their exposure to the inter- vention being studied. Patients entering controlled clinical trials should be ran- domized, meaning that all patients signed up for the trial should have an equal chance of being placed in either the control group (also called the comparison group, placebo group, or standardized therapy group) or the experimental group, which gets the intervention being tested. Subjects and experimenters should ide- ally be blinded to the therapy and group assignment during the study, such that the experimenters and subjects are unaware if the patient is in the control or experimental group, and are thus unaware whether they are receiving the exper- imental treatment or the comparison treatment. They can show that the cause and effect are associated more than by chance alone, that the cause precedes the effect, and that altering the cause alters the effect. When properly carried out they will have fewer methodological biases than any other study design. The most common weakness of controlled clinical trials is that they are very expensive. Because of the high costs, multi- center trials that utilize cooperation between many research centers and are funded by industry or government are becoming more common. Unfortunately, the high cost of these studies has resulted in more of them being paid for by large biomedical (pharmaceutical or technology) companies and as a result, the design of these studies could favor the outcome that is desired by the sponsoring agency. This could represent a conflict of interest for the researcher, whose salary and research support is dependent on the largess of the company providing the money. Other factors that may compromise the research results are patient attri- tion and patient compliance. There may be ethical problems when the study involves giving potentially harmful, or withholding potentially beneficial, therapy. It is still the reader’s responsibility to determine how valid a study is based upon the methodology. In addition, the fact that a study is a ran- domized controlled trial does not in itself guarantee validity, and there can still be serious methodological problems that will bias the results. Albert Einstein (1879–1955) Learning objectives In this chapter you will learn: r different types of data as basic elements of descriptive statistics r instrumentation and measurement r precision, accuracy, reliability, and validity r how researchers should optimize these factors All clinical research studies involve observations and measurements of the phe- nomena of interest. The instruments used to make them are subject to error, which may bias the results of a study. The first thing we will discuss is the type of data that can be generated from clinical research. This chapter will then introduce concepts related to instruments and measurements. They can be classified by their function as independent or dependent variables, their nature as nominal, ordi- nal, interval, or ratio variables, and whether they are continuous, discrete, or dichotomous variables. When classifying variables by function we want to know what the variable does in the experiment. The independent variable is under the con- trol of or can be manipulated by the investigator. Generally this is the cause we 67 68 Essential Evidence-Based Medicine are interested in, such as a drug, a treatment, a risk factor, or a diagnostic test. The dependent variable changes as a result of or as an effect of the action of the independent variable. It is usually the outcome of exposure to the treatment or risk factor, or the presence of a particular diagnosis. We want to find out if chang- ing the independent variable will produce a change in the dependent variable. The nature of each variable should be evident from the study design or there is a serious problem in the way the study was conducted. When classifying variables by their nature, we mean the hierarchy that describes the mathematical characteristics of the value generated for that vari- able. The choice of variables becomes very important in the application of statis- tical tests to the data. One can assign a number to each of these categories, but it would have no intrinsic significance and cannot be used to compare one piece of the data set to another. Exam- ples of nominal data are classification of physicians by specialty or of patients by the type of cancer from which they suffer. There is no relationship between the various types of specialty physicians except that they are all physicians and went to medical school. Ordinal data are nominal data for which the order of the variables has impor- tance and intrinsic meaning. Typical examples of ordinal data include certain pain scores that are measured by scales called Likert scales, severity of injury scores as reflected in a score such as the Trauma Score where lower numbers are pre- dictive of worse survival than higher ones, or the grading and staging of a tumor where higher number stages are worse than lower ones. Common questionnaires asking the participant to state whether they agree, are neutral, or disagree with a statement are also examples of an ordinal scale.

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Consistency of evidence The next feature to consider when looking at levels of evidence is the consistency of the results buy 2 mg trihexyphenidyl free shipping pain medication for dogs with osteosarcoma. Overall 2mg trihexyphenidyl free shipping treatment for nerve pain after shingles, it is critical that different researchers in different settings and at different times should have done research on the same topic cheap trihexyphenidyl 2 mg on line dfw pain treatment center. The results of these comparable studies should be consistent, and if the effect size is similar in these studies, the evidence is stronger. Be aware that less consistency exists in those studies that use different research designs, clinical settings, or study pop- ulations. A good example of the consistency of evidence occurred with studies looking at smoking and lung cancer. For this association, prior to the 1965 Sur- geon General’s report, there were 29 retrospective and 7 prospective studies, all of which showed an association between smoking and lung cancer. A single study that shows results that are discordant from many other stud- ies suggests the presence of bias in that particular study. However, sometimes a single large study will show a discordant result compared with multiple small studies. This may be due to lack of power of the small studies and if this occurs, the reader must carefully evaluate the methodology of all the studies and use those studies with the best and least-biased methodology. If a study is small, a change in the outcome status of one or two patients could change the entire study conclusion from pos- itive to negative. This means making sure that the cause in the study is the actual factor associated with the 194 Essential Evidence-Based Medicine effect. Often, the putative risk factor is confused with a confounding factor or a surrogate marker may produce both cause and effect. Specificity can be a problematic feature of generalization as there are usually multiple sources of causation in chronic illness and multiple effects from one type of cause. For example, before the advent of milk pasteurization, there were multiple diverse diseases associated with the consumption of milk. To attribute the cause of all these diseases to the milk ignores the fact that what they have in common is that they are all caused by bacteria. The milk is simply the vehicle and once the presence of bacteria and their role in human diseases were determined, it could be seen that ridding milk of all bacteria was the solution to preventing milkborne transmission of these diseases. Then the next step was inspecting the cows for those same diseases and eradicating them from the herd. For most causes of death, the increase in death rate in smokers is about double (200%) that of nonsmokers. However, for lung cancer specifically, the increase in the death rate in smokers is almost 2000%, an increase of 20 times. This lung cancer death rate is more specific than the increased death rate for other diseases. In those other diseases, smoking is a less significant risk factor, since there are multiple other factors that contribute to the death rate for those diseases. Temporal relationship The next characteristic that should be considered is the temporal relationship between the purported cause and effect. In order to have a temporal relationship, there should be an appropriate chronological sequence of events found by the study. The disease progression should follow a predictable path from risk-factor exposure to the outcome and that pattern should be reproducible from study to study. For example, some smokers quit smoking just prior to getting sick with lung cancer. While they may attribute their illness to quitting, the illness was present long before they finally decided to quit. In this case, the cancer may appear to be the cause and the cessation of smoking the effect. The causality may be difficult to determine in many cases, especially with slowly progressive and chronic diseases. Dose–response The dose–response gradient can help define cause and effect if there are varying concentrations of the cause and varying degrees of association with the effect. Usually, the association becomes stronger with increasing amounts of exposure Applicability and strength of evidence 195 to the cause. However, some cause-and-effect relationships show the opposite correlation, with increasing strength of association when exposure decreases. An example of this inverse relationship is the connection between vitamin intake and birth defects. As the consumption of folic acid increases in a population, the incidence of neural tube birth defects decreases. The direction and magnitude of the effect should also show a consistent dose–response gradient. This gradient can be demonstrated in randomized clinical trials and cohort studies but not in case–control or descriptive studies. In general, we would expect that an increased dose or duration of the cause would produce an increased risk or severity of the effect. The risk of lung cancer decreases among former smokers as the time from giving up smoking increases. In these cases, the risk is highest at both increased and decreased rates of exposure while it is lowest in the middle. For example, a recent study of the effect of obesity on mor- tality showed a higher mortality among patients with the highest and lowest body mass index with the lowest mortality among people with the mid-range levels of body mass index. Biological plausibility When trying to decide on applicability of study results, biological plausibility should be considered. The results of the study should be consistent with what we know about the biology of the body, cells, tissues, and organs, and with data from various branches of biological sciences. There should be some basic science in- vitro bench or animal studies to support the conclusions and previously known biologic mechanisms should be able to explain the results. Is there a reason in biology that men and women smokers will have different rates of lung cancer? For some medical issues, gender, ethnicity, or cultural background has a huge influence while for other medical issues the influence is very little. To determine which areas fall into each category, more studies of gender and other differences for medical interventions are required.