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* From the Acute Pain Research Unit, Department of Anaesthesia and Pain Management, University Health Network and Mount Sinai Hospital, Toronto, Ontario, Canada;
the Department of Anesthesia, Our Lady's Hospital, Navan Ireland;
the Regional Anesthesia and Acute Pain Service, University Health Network, University of Toronto, Toronto, Ontario, Canada; and
the Acute Pain Research Unit, Department of Anaesthesia and Pain Management, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.
Address correspondence to: Dr. Joel Katz, Department of Anaesthesia and Pain Management, University Health Network, EN 3-440, 200 Elizabeth Street, Toronto, Ontario M5G 2C4, Canada. Phone: 416-340-3777; Fax: 416-340-3698; E-mail: jkatz{at}uhnres.utoronto.ca
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Abstract |
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Methods: Demographic and health history information was collected from 621 female patients who were screened for inclusion in a pain management trial involving epidural anesthesia. Patients who completed the clinical trial (n = 149) were compared to those who consented to provide screening information but did not enter the trial (n = 472).
Results: Sixty-seven percent of women who refused cited unwillingness to have an epidural as the reason for their decision. Non-Caucasians (P < 0.01), patients with no history of mood/anxiety disorders (P < 0.016) or systemic disease (P < 0.02), and patients with certain types of pain (P < 0.02) were more likely to refuse to participate in the clinical trial. A longer duration between recruitment and surgery was also found to be associated with higher participation rates (P < 0.01). A logistic regression equation significantly predicted which patients would participate or refuse (P < 0.0001), indicating that a specific set of health and demographic factors strongly influence the decision to participate in a trial.
Conclusions: The decision to participate in a clinical trial is viewed as a risk/benefit analysis. Factors such as short recruitment to surgery intervals and pre-existing pain, which increase the salience of risks associated with the trial, may result in lower participation rates. Overall, epidural anesthesia is a strong deterrent to participation in a clinical trial.
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Introduction |
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The aim of this study is to compare patients who agreed to participate in a clinical trial involving epidural anesthesia with those who declined.
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Methods |
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Population
The target population was women between 19 and 75 yr of age undergoing major gynecological procedures by laparotomy. Patients with ASA scores > 2 or contraindications to any of the trial procedures were excluded.
Recruitment
Patients at two large urban teaching hospitals were approached by a research nurse at their pre-admission appointment. During screening, patients were asked to provide verbal consent to answer demographic and health history questions and have their chart reviewed. Eligible patients were given a standardized description of the clinical trial and asked to sign informed consent.
Patients were asked to enter a pain management trial involving epidural anesthesia. Epidural anesthesia is not standard practice for abdominal-gynecological surgery at either hospital; only patients who participated in the trial would receive an epidural.
Sample
The present study consists of two groups of women: the refuser group (n = 472) who consented to provide demographic and health history information and have their chart reviewed but declined to participate in the clinical trial; and the participant group (n = 149) who signed consent and completed the study or were withdrawn for protocol violations occurring intra-operatively or postoperatively. Patients who initially consented but dropped out before surgery (n =60) were not included.
Statistical analysis
Continuous variables were analyzed by multivariate ANOVA. Categorical variables were analyzed using chi- squared tests. P < 0.05 was considered statistically significant. Eighteen cases with outliers more than three standard deviations from the mean were removed from analysis.
Binary logistic regression was performed to predict whether patients would be likely to refuse or participate. Since cases with missing data could not be evaluated using the logistic regression, missing values were replaced for the logistic regression analysis, but only for variables with less than 10% of data missing.
The database was split in half randomly, using the SPSS "select cases" function choosing the "random sample of cases" option from the entire database with one half used to generate the regression equation and the other used to test it. The final model was chosen for low log likelihood (a measure of the probability of obtaining the observed results given the parameter estimates), parsimony and the ability to predict refusers and participants equally.
Data were analyzed using SPSS for Windows 9.0, Chicago, IL, USA.
Additional information regarding the clinical trial, a full list of variables analyzed, methods of replacing missing data and the logistic regression analysis are available at www.cja-jca.org.
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Results |
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To investigate the hesitation of many patients to receive an epidural, results were collapsed into two groups: those who refused to participate because of the epidural and those who refused for other reasons (Table I
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shows the results of the comparison between participants and refusers.
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). The area under the receiver-operator characteristics curve for the model was 0.7, indicating the model performed significantly better than chance (P < 0.0005). Table IV shows the variables included in the logistic regression equation.
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Discussion |
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Several factors were associated with lower participation rates in this sample. The fewer days before surgery patients were approached, the more likely they were to refuse. As the patient's surgery approached, it is possible that the potential risks weighed more heavily in the decision making process.
In addition, patients with certain types of pain were more likely to refuse. Patients with abdominal and back pain had higher rates of refusal than patients without pain. This was not observed for patients with headache or other types of pain. Patients with back pain may have been more hesitant to have an epidural, while patients with abdominal pain may have been more apprehensive about their impending abdominal surgery and unwilling to undergo additional interventions.
The data also suggest that prior experience in a medical setting may increase the likelihood that a patient will consent. Patients with a history of systemic disease, diagnosed mood or anxiety disorders or greater number of previous surgeries were more likely to participate. These patients likely had more contact with the medical system than asymptomatic patients. This may have reduced the perceived risk and uncertainty associated with participating. While these results do not conclusively support this interpretation, they suggest an area for future research.
The salience of reduced postoperative pain as a potential benefit of research also merits further study. The clinical trial studied here involved no treatment for the patient's primary diagnosis. The potential for improved treatment increases the likelihood that a patient will participate in research.4 Determining the importance to the patient of improved pain management may help predict whether a patient will participate in a clinical trial of this type.
The results confirm previous findings5 that epidural anesthesia is a deterrent to participation in a clinical trial. Resistance to epidural anesthesia as presented in the context of a clinical trial appears to be related to age, with younger persons more likely to refuse because of unwillingness to have an epidural. The nature and origins of these attitudes require study.
The unpopularity of epidural anesthesia also raises questions about the generalizability of these results. Would patients who refused due to the epidural have participated in other research that did not involve epidural anesthesia? Would they have consented to an epidural had it been in the context of routine clinical practice? Further research is needed to determine the extent to which the results obtained here can be generalized to clinical trials with different risk/benefit profiles.
Finally, there is an inherent difficulty in obtaining an accurate portrait of patients who refuse to participate in clinical trials. Our refuser group consisted of patients who agreed to be screened. However, there is no ethical way of obtaining data from the "true refusers" who will not provide any information for research purposes.
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Footnotes |
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Institutes of Health, Bethesda, Maryland. Presented in part at the 20th Annual Scientific Meeting of the American Pain Society, Phoenix, Arizona, USA (April 20, 2001).
Revision received March 13, 2002. Accepted for publication January 14, 2002.
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References |
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2 Ross S, Grant A, Counsell C, Gillespie W, Russell I, Prescott R. Barriers to participation in randomised controlled trials: a systematic review. J Clin Epidemiol 1999; 52: 1143–56.[Medline]
3 Barofsky I, Sugarbaker PH. Determinants of patient nonparticipation in randomized clinical trials for the treatment of sarcomas. Cancer Clin Trials 1979; 2: 237–46.
4 Charlson ME, Horwitz RI. Applying results of randomised trials to clinical practice: impact of losses before randomisation. Br Med J Clin Res Ed 1984; 289: 1281–4.
5 van den Berg L, Lobatto RM, Zuurmond WWA, de Lange JJ, Wagemans MFM, Bezemer PD. Patients' refusal to participate in clinical research. Eur J Anaesthesiol 1997; 14: 287–9.[Medline]
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