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Revista Española de Cardiología is an international scientific journal devoted to the publication of research articles on cardiovascular medicine. The journal, published sinceis what is statistical treatment in research example official publication of the Spanish Society of Cardiology statisttical founder of the REC Publications journal family. Articles are published in both English and Spanish in its electronic edition.
The Impact Factor measures the average number of citations received in a particular year by papers published in the journal during treatmenh two preceding years. SRJ is a prestige metric based on the idea that not all citations are the same. SJR uses a similar algorithm as the Google page rank; it provides a quantitative and what is statistical treatment in research example measure of the journal's impact.
SNIP measures contextual citation impact by wighting citations based on the total number of citations in a subject field. The evidence on the efficacy of a treatment or intervention derives from randomized clinical trials, which have the best design to assess treatment efficacy. Thus, there is a selection bias that may indicate that the observed treatment effect could be related to the baseline characteristics of the treated and untreated patients rather than to the treatment itself.
Multivariate statistical analysis is normally employed to control the differences, but these methods wxample not perfect. InRosenbaum and Rubin 5 proposed a new method for controlling this bias: calculating the individual probability, influenced by certain covariates, of receiving a treatment, the propensity score PS. In recent years, the use of this method in observational studies is increasing considerably.
The main objective of this report is to present a practical application of rewearch statistical method, discussing its advantages and limitations. We analyze the association between myocardial reperfusion therapy and day lethality what is a linear model meaning patients with acute myocardial infarction AMI ranging between 25 reseagch 74 years of age who reached a hospital alive within the first 12 hours of onset of symptoms and were enrolled in the IBERICA Research, Specific Search and Registry of Acute Coronary Events study.
The study design, methods and quality controls have been database best practices node.js in detail elsewhere. We present the data from patients who reached the hospitals of the participating localities alive.
The study period began on 1 January and ended on 31 December Case Identification and Classification. For the detection of patients hospitalized with AMI, a search was carried out in all the hospitals of the participating localities; the sources of information were the coronary care units CCUtreatmrnt cardiology service, hospital admission and emergency room records and death certificates. AMI was considered to be definite in living patients when a Q wave was present on an electrocardiogram or in the presence of electrocardiographic changes suggestive of ischemia, with typical symptoms and myocardial enzyme creatine kinase levels more than two-fold higher than the maximum reference value.
In those who died, AMI was considered to be definite when autopsy revealed signs of coronary thrombosis or recent myocardial necrosis. The possible AMI group consisted of individuals who did not meet the criteria for definite AMI and died with the typical symptoms or when autopsy revealed signs of coronary arteriosclerosis or ischemic heart disease. In each registered case, information was collected on the administration of reperfusion therapy, distinguishing between thrombolysis and percutaneous coronary intervention PCI.
In patients who underwent thrombolysis, the delay between hospital arrival and treatment door-to-needle time was recorded. In addition, information was gathered on their cardiovascular risk factors, history of ischemic heart disease reaearch heart failure, and clinical variables related to the AMI AMI site and Killip class on admissionas well as hospital type basic, without CCU or hemodynamic laboratory; intermediate, with CCU but no hemodynamic laboratory; or advanced, with both facilities and CCU admission.
The vital status at 28 days was ascertained by means of clinical follow-up and death records. The analysis of the association between reperfusion therapy and the day case lethality was performed using logistic regression models, including the confounding variables and certain clinically relevant variables. The PS for receiving thrombolysis, PCI or either of the 2 reperfusion therapies was calculated on the basis of the demographic and clinical characteristics of each patient.
The advantage of logistic regression is that the variables do not have to show a normal distribution. In our example, all the demographic and clinical characteristics what is statistical treatment in research example all the bivariate interactions between these variables were initially included in 3 different logistic regression models to predict the utilization of these reperfusion therapies. Where Z is the therapy analyzed and X 1 and X n are the covariables that predict its use.
The discriminatory power of each of these models was analyzed by calculating the area under the receiver operating characteristic ROC curve. The models were considered to have a good discriminatory power statisticak this area was greater than or equal to 0. Once the PS was calculated, one of three different analytical strategies could be employed.
Another possible strategy is to match treated and untreated patients. Several methods for achieving these matches have been proposed. These differences can be ezample by comparison of means and proportions or by calculating the standardized differences between treated and untreated patients. A third analytical strategy involves the stratification of the patients included in the analysis. The data corresponding to this analytical strategy are not presented here.
Finally, to evaluate what is statistical treatment in research example effect of missing data on the PS for receiving therapy, we compared the characteristics of the patients for whom the data was insufficient and those for whom complete valid data had been collected. Two strategies were used to analyze the effect of these cases. In one, the missing data required for the calculation of the PS were completed with the medians of each of these variables.
A total of AMI in patients between the ages of 25 and 74 years who reached a hospital alive were registered during the study period. Information concerning the time treatmment between the onset of symptoms and arrival at a hospital was not available in cases 8. In all, patients reached the hospital within 12 hours of the onset of symptoms; it was not known whether reperfusion had been performed in 26 of these cases 0. The differences between the patients who underwent myocardial reperfusion and those who did not are summarized in Table 1.
In the untreated group, the patients were older and there were higher proportions of women, of patients with histories of hypertension, diabetes, prior AMI, angina, and heart failure, of patients with non-Q wave myocardial infarction, higher Killip class on admission and a longer delay in reaching the hospital, while there were lower proportions of smokers resesrch patients admitted to the CCU.
The day case lethality of patients who did not undergo reperfusion therapy was higher than that of the treated patients. Table 2 shows the variables included in the logistic regression model to calculate the PS for receiving reperfusion therapies being evaluated and the area under the ROC curve, used to estimate the discriminatory wyat of the calculated PS, which was greater than or equal to 0. The treated and untreated patients were matched on the basis of the PS for receiving therapy, which resulted in the matching of patients.
Treatent within-pair differences were observed in the major variables of interest Table 3. The absolute standardized differences in the demographic and clinical variables of interest observed in the analysis of all the treated and untreated patients nearly disappeared when the matched patients were analyzed Figure what is statistical treatment in research example.
We were unable to match patients because the treated and untreated individuals differed widely in terms of both the distribution of cases according to the logit of the PS for treatment and the range of values of this PS Figure 2. Table 3 also shows the differences between unmatched treated and untreated patients. In the multivariate logistic regression analysis, after adjustment for confounding variables, thrombolysis and PCI, whether considered separately or together, were significantly associated with a lower day lethality rate Table 4A.
When the PS for receiving these reperfusion therapies was included in the models, only PCI was found to have a statistically significant association with a lower case lethality treatmet Table 4B. When the matched pairs of treated and untreated patients with the same PS for receiving researchh were analyzed, no statistically significant association was observed between the reperfusion therapies and the case lethality rate Table 4C.
The PS for undergoing thrombolysis, PCI or either of the 2 reperfusion therapies could not be calculated in cases in which the data for one or more of the variables included in the model was missing. These cases were associated with a higher risk than those in which the PS for receiving therapy could be calculated older age, greater comorbidity, more severe infarction and with statisticwl higher lethality rate Table 5. This group also had a lower proportion of patients who had received reperfusion therapy, although the differences were not statistically significant Table 5.
Table examppe shows the results of the analysis in which the missing data that impeded the calculation of the PS for receiving therapy were completed with what is the meaning of bad mood in tagalog corresponding medians, as well as the results of the multiple imputation analysis of values with missing data. The results of these two teatment strategies indicate that thrombolysis and PCI, whether considered separately or together, were associated with a lower day case lethality rate Table 6.
In this study, we present a practical application of a statistical method that involves the calculation of the probability of receiving therapy, the PS, in order to analyze the effectiveness of this approach in observational studies. The analysis of the association between a treatment and an event of interest in observational studies is complex since, in contrast to randomized ib trials, the treated and untreated groups may differ widely with respect to many covariates.
If these covariables are associated with the event of interest, it may prove difficult to determine whether the effect of the treatment can be attributed to the differences in these covariables. The calculation of the PS for receiv ing a treatment is a method that enables statisgical statistician to reduce the bias caused by the differences between treated and untreated patients. Thus, in the design of an observational study to analyze the effect of a treatment, it is important to gather information on all the variables that can be related to the use of exampl treatment being studied.
If the discriminatory power why is my video call not working the models predictive of treatment what is statistical treatment in research example adequate, it can be assumed that the regression models that include the calculated PS for receiving treatment will be able to provide unbiased estimations of the treatment effect.
In the real-world example we describe, using the classical multivariate analysis, thrombolysis, PCI and reperfusion with either of the 2 methods were associated with lower day lethality rates. When the PS for receiving these therapies was included, what is statistical treatment in research example presented no association with lethality, while PCI continued to be associated with a lower rate. The disappearance of this association between thrombolysis and lethality may be related to a more precise control of the confounding what is client relationship management software achieved with the introduction of the calculated PS or, as we will discuss below, to a selection bias in the analysis produced by the exclusion of a group of patients for whom data required for the calculation of the PS was missing.
In theory, the same results should be obtained whether the Statisticl for receiving therapy or all the covariates employed to calculate this PS are included in the models utilized to analyze the treatment effect. In the second stage, only this PS what is statistical treatment in research example a group of more relevant variables are included. If we were to include all the variables and interactions in the model to analyze the association between treatment and the event of interest, the interpretation of the final model and the analysis of its validity would be much more complex.
The matching of treated and untreated patients with the same PS for receiving treatment is a widely used analytical strategy. With this approach, the treated and untreated groups are found to have highly similar characteristics with respect to all the covariables, an ideal situation for analyzing the association between treatment and the event of interest, similar to that obtained in randomized clinical trials. In any case, we should take into account the fact that patients were matched on the basis of the variables introduced into the model to calculate the PS for receiving treatment and that, depending on the treatment, there may be within-pair differences with regard to other variables that were not considered in this calculation.
In our study, matching was highly effective and we obtained a subgroup of patients that differed only in the use of reperfusion therapy Table 3 and Figure 1. Matching is limited by the fact that if the degree of overlap of the distribution of the PS for receiving treatment in treated and untreated patients is small, as occurs in our study Figure 2many patients cannot be matched.
Moreover, these unmatched patients differ widely depending on whether or not they received therapy and differ with syatistical to the matched patients Table 3. This means that the individuals included what is statistical treatment in research example the matched-pair analysis are a selection of patients from the overall group with given characteristics, thus limiting the generalization of the results obtained what is causal logic in english the population, which was the ultimate objective of our analysis.
In the data from our real-world example, we observe what is statistical treatment in research example neither thrombolysis nor reperfusion using PCI was associated with lethality in the matched-pair analysis Table 4C. Such widely atatistical results are probably due to the patient selection carried out for this matched-pair analysis, and do not represent a valid estimator of the association between reperfusion and lethality.
Figure 1. Absolute standardized differences between patients treated or not treated with reperfusion when the overall group wyat considered b and when matched according to the propensity score for receiving reperfusion therapy j. An absolute difference of between 1 and 10 was considered to be statistically what is statistical treatment in research example vertical dashed line.
Figure 2. What is statistical treatment in research example of the logit of the probability of receiving reperfusion therapy for all the treated A and untreated B patients. One of the limitations of the analysis based on the PS for receiving treatment is the exclusion statitical a group of patients in whom this PS could not be calculated because the data for one or more of the variables included in the model predictive of treatment were missing.
As we mentioned above, the disappearance of this association may have occurred because, with the introduction of the PS for undergoing reperfusion, we excluded a subgroup of patients with missing data relative to this variable, thus introducing a potential selection bias into the analysis. Indeed, there was a group of patients with a greater risk, higher case fatality and a trend toward a lower utilization of reperfusion therapy that was not included in the analysis because the PS for receiving treatment could not be calculated due to missing data relative to one or more of the variables of the predictive model Table 5.
The exclusion of these patients may have introduced a bias in the results that would reduce the efficiency of the estimator of the effectiveness of reperfusion. Both the analysis that assigned the corresponding median to the variables for which the data was missing and the multiple imputation analysis Table 6 support the existence of this bias. They also demonstrate the effectiveness of thrombolysis, PCI or reperfusion using either of the 2 methods in reducing lethality associated with AMI in our population Table 6.
Statlstical data are consistent with those observed in clinical trials. Characteristics, Clinical Implications and Limitations of the Study. The IBERICA study enables the what does associate mean before a job title of the care provided to AMI patients on a population-wide scale, as well as its effectiveness which are the healthiest fast food restaurants real-world conditions in clinical practice.
There are certain limitations due to the unavailability of a the electrocardiographic features of the infarction at the time of hospital admission ST-segment elevation, etc. However, when the analyses were repeated after selecting cases of Q wave AMI as an estimate of patients with ST-segment elevation and introducing the median delay where this information was missing, the results were very why wont my laptop find internet connections data not shown.
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