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At least 19 recordsLinked to original sources
PubMed2001

[Comparative study on antibody levels of vaccination group and control group after 4 years of immunized with type B inactivated vaccine against hemorrhagic fever with renal syndrome].

OBJECTIVE: To compare the antibody level of vaccine group and control group in a randomized, controlled trial of type B inactivated vaccine against hemorrhagic fever with renal syndrome(HFRS) in Jiande County of Zhejiang Province and to find out if there is enhancement of subclinical infection about type B inactivated vaccine against HFRS. METHODS: The number of sera collected (July 1994-July 1998) in vaccine group immunized type B inactivated vaccine against HFRS and control group were 305 and 283 persons in Jiande County respectively, and indirect immunofluorescent antibody method(IFAT) was used for testing the titer of HFRS IgG in sera. The cut-off values were determined on IFA titer of the second sera in control group with positive and negative IFA before vaccine was given respectively, and the subclinical infection of positive and negative IFA of the first sera in vaccine group was evaluated. RESULTS: When taking different cut-off values of subclinical infection, there were no statistical differences in HFRS IFA positive rates between vaccine group and control group of positive IFA in the first sera. In vaccine group and control group of negative IFA before vaccine given, also the IFA positive rates were not statistically different in these groups. There were no statistical differences of IFA GMT and IFA sero-negative rate between vaccine group and control group. CONCLUSIONS: The investigation showed there was no statistical difference in antibody level between vaccine group and control group, so there could not be enhancement of subclinical infection of vaccine group receiving type B inactivated vaccine against HFRS.

Adolescent↗
PubMed1986

A comparison of randomized concurrent control groups with matched historical control groups: are historical controls valid?

The use of a historical control group is predicated on the assumption that survival and relapse-free survival in the historical control group closely approximate the survival and relapse-free survival in a randomized concurrent control group. This assumption has never been tested. This study compares survival and relapse-free survival in randomized control groups with historical control groups matched for disease, stage, and follow-up. Of the 43 matched control groups, 42% varied by more than 10 percentage points, 21% varied by more than 20 percentage points, and 5% varied by more than 30 percentage points. Of the 18 that varied by greater than 10 percentage points, 17 had superior survival or relapse-free survival in the randomized concurrent control group. This study indicates that the assumption that historical control groups may replace randomized concurrent control groups is not valid.

Humans↗
PubMed1982

Controlled group designs in biofeedback research: ask, "What does the control group control for?".

The extant literature on the specific role of biofeedback in promoting skeletal muscular relaxation is reviewed and found deficient with respect to the use of properly controlled group outcome research. The review emphasizes the failure of commonly used control procedures to adequately control a number of potentially confounding variables. Strengths and weaknesses of three types of controlled group design (attention placebo, pseudofeedback, and altered contingency) are discussed with respect to their relative usefulness in controlling certain nonspecific or placebo effects in biofeedback research. Many published biofeedback studies failed to measure the credibility of control procedures or the subject's ability to discriminate different feedback contingencies. The studies reviewed suggest that the various control procedures used are not inert and are not equivalent with respect to their effects on control group behavior. The suggestion is made that the controlled group outcome design be accepted as the minimum requirement for testing the specific effects of biofeedback, and possible methods for improving control procedures are discussed.

Biofeedback, Psychology↗
PubMedDate not supplied

A note on the selection of control groups and control variables in comorbidity research.

Recently, investigators have become interested in "comorbidity" in eating disorders (EDs). However, it appears that many investigators fail to appreciate that demonstrating that ED patients have more of a given type of concomitant psychopathology than would be expected by chance requires the rejection of the following two null hypotheses: H0-1, Persons with EDs have no more symptomatology of the putatively comorbid condition than do persons without ED; and H0-2, Persons with EDs have no more symptomatology of the putatively comorbid condition than they have other kinds of psychopathology not specific to ED. The choice of proper control group for testing H0-1 and the necessity of testing H0-2 are illustrated with simulated data. These same general issues apply to the assessment of comorbidity in other conditions, but the appropriate comparison group obviously changes according to the exact hypothesis being tested.

Borderline Personality Disorder↗
PubMed1990

Prolonged treatment (18 months) of chronic hepatitis C with recombinant alpha-interferon in comparison with a control group.

The effectiveness of recombinant alpha-interferon was evaluated in chronic non-A, non-B hepatitis of parenteral transmission. Thirty patients were randomly allocated two groups: control group (without treatment) and treatment group (alpha-interferon 5 mega units thrice weekly for 2 months, and then 1.5 mega units until the eighteenth month). Retrospectively, 26 patients had anti-hepatitis C antibodies. After the first month, 40% of the treated patients had normal serum alanine aminotransferase levels, and no one in the control group (p less than 0.05). After 18 months of treatment, 40% (6/15) of treated patients and 7% (1/14) of controls had normal serum transaminases (p less than 0.05). Interferon was well tolerated. A decrease in the Knodell Index score on final biopsy was found in treated patients (p less than 0.05), with no variations in the control group. Relapse within 7 months after the end of treatment occurred in two out of six complete responders. Thus, recombinant alpha-interferon therapy given for 18 months normalizes serum transaminases and improves histological lesions in chronic hepatitis C of parenteral epidemiology. This long-term interferon schedule is well tolerated.

Adult↗
PubMed2006

Prevalence and factors associated with use of placebo control groups in randomized controlled trials in psoriasis: a cross-sectional study.

BACKGROUND: The ethics and science of using placebo control groups in clinical trials have been widely debated. Few studies, however, have examined factors associated with choice of control group. OBJECTIVE: Our aim was to assess the prevalence of use of placebo controls in randomized controlled trials in psoriasis and to identify factors associated with use of placebo controls in these trials. METHODS: This is a cross-sectional study of randomized controlled trials in psoriasis published from January 1, 2001 to December 20, 2005 and indexed in the Cochrane Central Register of Controlled Trials. We extracted data on types of control groups used, design issues (number of patients enrolled, primary end point), disease characteristics (psoriasis type and severity), and extrascientific issues (trial location, funding source, and year of publication). We used bivariable and multivariable logistic regression to determine factors associated with use of a placebo control group. RESULTS: Of 194 citations, 187 were available for review. One hundred thirty-five trials from 134 articles in 38 journals met inclusion criteria. Eighty-three trials (61.5%) enrolling 8171 subjects (41.7%) used active controls only, and 52 trials (38.5%) enrolling 11,406 subjects (58.3%) used placebo controls. Adjusted for trial location and funding source, trials significantly more likely to have used placebo controls included those conducted in the United States (odds ratio [OR], 5.79; 95% confidence interval [CI], 2.45-13.68; P < .001) and those funded by pharmaceutical companies (OR, 2.61; 95% CI, 1.19-5.73; P = .02). Predicted frequencies of placebo use ranged from 77.6% (industry-funded, conducted trials in the United States) to 18.6% (non-industry-funded trials not conducted in the United States). LIMITATIONS: Our searches may not have identified all published trials, and we did not have access to data from unpublished trials. CONCLUSIONS: Use of placebo controls has been more common in psoriasis trials conducted in the United States and funded by pharmaceutical companies. The findings suggest that ethical and scientific issues related to choice of control group in psoriasis trials are interpreted markedly differently depending on trial location and funding source.

Cross-Sectional Studies↗
PubMed1997

Near fatal asthma and psychopathological characteristics: a group-control study.

Psychological factors may play a role in asthma. In particular, emotional upsets have been correlated with fatal asthma attacks, and an abnormal personality attitude is considered to be a risk factor in fatal asthma. Moreover, some authors have recently reported favourable asthma outcome in patients with severe asthma and psychiatric abnormalities, when psychoactive treatment was initiated. On the understanding that people with fatal and "near fatal asthma" (NFA) are components of the same subset of the asthmatic population, we undertook a study aimed at assessing the importance of personality and psychiatric factors in asthma mortality. Between June 1991 and December 1993, a sample of 17 patients with asthma who had experienced one or more near fatal asthma attacks (respiratory arrest, or need for respiratory assistance, or altered conscious state, or arterial carbon dioxide tension (Pa,CO2) > 6.7 kPa (50 mmHg)), and 17 control patients with asthma who had never experienced such an attack (control group) were enrolled. All patients underwent: 1) an interview concerning their personal and family psychiatric history; 2) a psychodiagnostic investigation by a battery of four of the most widely used psychiatric tools: Hamilton scales for anxiety and depression; Zung scales for anxiety and depression; and Minnesota Multiphasic Personality Inventory. No statistical difference was found in psychodiagnostic tests between study and control groups. The psychiatric history was similar in the two groups. Our results suggest that personality characteristics and psychiatric history are not related to asthma outcome, and that the psychiatric approach is not expected to be useful in preventing mortality in asthma.

Adult↗
PubMed1994

Associations between the mental health and social networks of children and parents in single-parent families. A comparison between a clinical group and a control group.

The parents and children in single-parent families were studied. A group of 39 children ages 9-16 years who had been patients at a child and adolescent psychiatric clinic and a control group with an equal number of children were interviewed together with their single parent regarding social network and mental health. The networks of children and parents in the control group were more similar to each other than the networks of parents and children in the patient group. The crosswise influence of parents' mental health, children's behavioral disturbances and social networks showed associations between parents' mental health and children's behavioural disturbances, between parents's social networks and children's behavioural disturbances and between parents' mental health and their social networks. There was, on the other hand, no association between parents' mental health and the social networks of their children.

Adolescent↗
PubMed1996

Non-parametric methods for comparing multiple treatment groups to a control group, based on incomplete non-decreasing repeated measurements.

In the comparison of two or more treatment groups to a control group, consider a study with non-decreasing repeated measurements of the same characteristic taken over a common set of time points for each subject. Based on the vector of possibly incomplete responses from each subject, this paper considers asymptotically distribution-free tests of the equality of the groups. I propose consistent point estimators of the overall treatment differences and I derive non-parametric simultaneous confidence regions for the treatment effects. An example using data from a bladder cancer study illustrates the proposed methods.

Chi-Square Distribution↗
PubMed1983

Changes in personal construing in three psychotherapy groups and a control group.

Two repertory grids were administered at four-weekly intervals to members of three psychotherapy groups and one waiting-list control group. Individualized and general predictions of possible therapeutic change were made. More individualized than general predictions were confirmed, adding further support to the use of client-centred outcome measures. The outcome data indicated significant improvement in each therapy group. Process results were consonant with Yalom's (1970) curative factors of universality, modelling and family re-enactment and Malan's (1979) resolution of triangle of person. Finally, a model for further evaluation of group psychotherapy is outlined developing personal construct methodology within a group setting.

Adult↗
PubMedDate not supplied

[Prevention of caries in a district. Comparison of a target group with a control group at 7 years].

In the trial of the Ussl n. 19 it is developing since a period a specific program for prevention of the caries on a target group (Progetto città murata). For the verification of the efficiency, it was compared the oro-dental situation of the same group in a territory near and similar in socio-economic characteristics. It was emerged a better oro-dental situation in the target group with respect to the control-group. In fact the children who have undergone the therapy of the PCM do not only demonstrate better indices of DMF at seven years, but also a major adhesion to the fluorophylaxis.

Child↗
PubMed2003

Comparison of the cardiopulmonary response to exercise in recipients of dual sensor DDDR pacemakers Versus a Healthy control group.

The authors previously have shown in healthy subjects that age related loss of muscular strength did not alter the chronotropic response during treadmill exercise, whether with sudden onset of effort, as in the chronotropic assessment exercise protocol (CAEP) or more gradual effort as in the Harbor exercise protocol. This study was performed to verify that in patients suffering from chronotropic insufficiency, and in absence of other effort-limiting disorders, "physiologic" pacing enables a cardiorespiratory response comparable to that of age-matched healthy subjects. Furthermore, the aim of the study was to confirm that the response of a new dual sensor-based pacing system was properly adapted to the metabolic demand, whether during CAEP or during Harbor test, by subjecting patients to both protocols. All study participants were able to undergo treadmill exercise testing, had normal cardiopulmonary function tests at rest, and no cardiac, muscular, or pulmonary disease. A healthy group (control) included 16 subjects (mean age 70.4 +/- 3.9 years), and the test group (pacemaker [PM] included 9 subjects (mean age 67.1 +/- 10.8 years) permanently paced for isolated chronotropic insufficiency with a dual sensor pacing system. All subjects underwent CAEP and Harbor tests with measurements of gas exchange, 24 hours apart, in randomized order. All subjects reached an appropriate level of exercise, as expressed by mean lactate plasma concentrations, which were slightly higher in the control than the PM group during CAEP (4.9 +/- 1.9 vs 3.7 +/- 1.9 mmol/L, NS) and Harbor (5.3 +/- 1.9 vs. 3.8 +/- 1.8 mmol/L, P < 0.05) tests. No statistical difference was observed in VO2 and VE at peak exercise between the two groups during either test. In the PM group, heart rate at peak exercise and metabolic reserve slope were higher during the CAEP than the Harbor protocol. These two measurements were significantly lower than in the control group. The PM group also had lower plasma lactate concentrations and dyspnea/fatigue scores. The Harbor test seems less suitable than the CAEP test to study the chronotropic response of pacemakers with dual sensors during exercise. A high performance of the new dual sensor-based pulse generator was confirmed in this physically fit patient population, whose peak heart rate was considerably higher than in other similar studies.

Aged↗
PubMed1995

Measuring effectiveness. What to expect without a randomized control group.

Randomized controlled trials or studies are often considered the ideal way to evaluate the effectiveness of a treatment compared to a control. In such a study, the randomization procedure ensures that the subjects receiving the treatment and control are equal with respect to all conditions except for receiving the treatment or the control. Differences found by statistical comparisons of the results of such a study can be attributed to the effect of the treatment or how much the treatment differs from the control when all other things are held constant. Randomized controlled trials are not always possible, and even when possible they are often performed with such restrictions that they do not provide the true measure of the effectiveness of the treatment in the "real world" or under "conditions of usual practice." This article reviews the use of nonrandomized studies to measure effectiveness when a randomized control group is not available. Various types of nonrandomized studies are reviewed, along with their advantages and disadvantages. Often, these studies require statistical adjustments such as matching or covariance analysis to adjust for inequalities or to remove biases between the treatment and control groups; these are reviewed as well.

Clinical Trials as Topic↗
PubMed2004

Control group selection in critical care randomized controlled trials evaluating interventional strategies: An ethical assessment.

BACKGROUND: Ethical concern has been raised with critical care randomized controlled trials in which the standard of care reflects a broad range of clinical practices. Commentators have argued that trials without an unrestricted control group, in which standard practices are implemented at the discretion of the attending physician, lack the ability to redefine the standard of care and might expose subjects to excessive harms due to an inability to stop early. OBJECTIVE: To develop a framework for analyzing control group selection for critical care trials. METHOD: Ethical analysis. RESULTS: A key ethical variable in trial design is the extent with which the control group adequately reflects standard care practices. Such a control group might incorporate either the "unrestricted" practices of physicians or a protocol that specifies and restricts the parameters of standard practices. Control group selection should be determined with respect to the following ethical objectives of trial design: 1) clinical value, 2) scientific validity, 3) efficiency and feasibility, and 4) protection of human subjects. Because these objectives may conflict, control group selection will involve trade-offs and compromises. Trials using a protocolized rather than an unrestricted standard care control group will likely have enhanced validity. However, if the protocolized control group lacks representativeness to standard care practices, then trials that use such groups will offer less clinical value and could provide less assurance of protecting subjects compared with trials that use unrestricted control groups. For trials evaluating contrasting strategies that do not adequately represent standard practices, use of a third group that is more representative of standard practices will enhance clinical value and increase the ability to stop early if needed to protect subjects. These advantages might come at the expense of efficiency and feasibility. CONCLUSION: Weighing and balancing the competing ethical objectives of trial design should be done for each trial.

Control Groups↗
PubMed1991

Bacteriological autopsy. II. Comparison of a group of cancer patients with a control group.

A study of the results of bacteriological autopsy in a group of cancer patients compared with a control group was carried out. Autopsy was performed on 42 bodies within 24 hours of death. Thirty-two patients had died with a cancer and the remaining ten had died of cardiovascular disease. Tissue for microscopy and material and culture were taken from the same sites. The results of the inoculations were semiquantified, resulting in a culture score, and the results of the microscopy were classified according to presence of bacteria and kind of inflammation. Furthermore, grading was done according to the degree of inflammation and whether bacteria were seen at microscopy. The culture scores were significantly higher in the cancer group than in the control group. We found a significant correlation between score and presence of acute inflammation. Likewise, a significant correlation was found between score and presence of bacteria at microscopy. As a difference between the cancer group and the control group was seen, further research on bacteriological autopsy seems worthwhile.

Adult↗
PubMed2003

[Comparison of fat consumption by patients with large bowel adenomas and control group].

STUDY AIM: Analysis of differences in fat consumption (total fat, saturated, monounsaturated and polyunsaturated acids) and cholesterol between patients with large adenomas (study group, GB) and control group (GK). MATERIAL AND METHODS: GB and GK patients were recruited from the patients undergoing full colonoscopy during routine work of endoscopy unit. The whole material included 111 patients: 57 patients with large bowel adenomas and 54 without large bowel adenomas. The intake of fat was assessed using a method calculating intake during 30 days preceding the study. RESULTS: In the group of studied women versus control group women no significant differences were found in consumption including energy value of diet (1755.8 kcal vs 1925.0 kcal), total protein (69.1 g vs 76.1 g), carbohydrates (237.2 g vs 258.0 g). Similarly, in the group of studied men no significant differences were found in the consumption of total protein (84.6 g), carbohydrates (275.7 g) and energy (2126.9 kcal) in relation to control group in which the respective values were: 98.4 g, 336.1 g and 2612.8 kcal. In the group of studied women the mean fat consumption was 67.2 g while in the control group it was 73.4 g. The mean intake of saturated fatty acids was 24.0 g and 25.2 g respectively. The consumption of monounsaturated and polyunsaturated fatty acids was in these group 27.1 g and 10.5 g vs 30.5 g and 11.9 g. The differences were statistically not significant. No difference was found in cholesterol intake between women in the study group and those in control group (245.8 mg and 280.0 mg respectively). The male study group was not differing significantly from the control group in the consumption of total fat (83.6 g vs 102.3 g), saturated fatty acids (29.7 g vs 37.5 g), monounsaturated and polyunsaturated fatty acids (34.2 g vs 42.1 and 13.0 g 14.7 g) and cholesterol (335.0 mg vs 420.4 mg). CONCLUSION: No correlation was found between the consumption of total fat, saturates, monounsaturated and polyunsaturated fatty acids and the occurrence of large bowel adenomas.

Adenoma↗
PubMed2005

Impact of severity of illness bias and control group misclassification bias in case-control studies of antimicrobial-resistant organisms.

BACKGROUND: Case-control studies often analyze risk factors for antibiotic resistance. Recently published articles have illustrated that randomly selected control-patients may be preferable to those with the susceptible phenotype of the organism. A possible methodologic problem with randomly selected control-patients is potential bias due to control group misclassification. This occurs if some control-patients did not have clinical cultures performed and thus might have been unidentified case-patients. If this bias exists, these studies might be expected to report lower odds ratios (ORs) because control-patients would be more like case-patients. OBJECTIVE: To analyze potential biases that might arise due to control group misclassification and potentially larger selection biases that may be introduced if control-patients are required to have at least one clinical culture. PATIENTS: One hundred twenty case-patients, 770 control-patients in group 1, and 510 control-patients in group 2. METHODS: Two case-control studies. Case-patients had clinical cultures positive for imipenem-resistant Pseudomonas aeruginosa. The first group of control-patients were random. The second group of control-patients were identical to those in group 1 except being required to have at least one clinical culture. RESULTS: Univariate analyses showed higher ORs for case-patients versus control-patients in group 1 (imipenem [OR, 12.5], piperacillin-tazobactam [OR, 3.7], and vancomycin [OR, 4.7]) as compared with case-patients versus control-patients in group 2 (imipenem [OR, 8.0], piperacillin-tazobactam [OR, 2.5], and vancomycin [OR, 3.0]). CONCLUSION: Requiring control-patients to have at least one clinical culture introduces a selection bias likely because it eliminates patients with less severe illness.

Anti-Bacterial Agents↗
PubMed2006

Improving the quality of randomized controlled trials in Chinese herbal medicine, part II: control group design.

OBJECTIVE: To discuss the types of control groups in randomized controlled trials (RCTs) of Chinese herbal medicine (CHM), and to provide suggestions for improving the design of control group in future clinical studies in this therapeutic area. METHODS: A search of the Cochrane Library was conducted in July 2005 to identify RCTs of CHM, and 66 RCTs with CHM for type 2 diabetes mellitus were obtained as the basis for further analysis. RESULTS: Of 66 RCTs with CHM for type 2 diabetes mellitus, 61 (92.4%) trials had both a treatment group and a control group. Twenty-seven (40.9%) RCTs compared CHM plus conventional drug vs conventional drug, 24 (36.4%) compared CHM vs conventional drug, 5 (7.6%) compared CHM vs placebo, 3 (4.5%) compared CHM plus conventional drug vs conventional drug plus placebo, 3 (4.5%) compared CHM plus conventional drug vs other CHM, 1 (1.5%) compared CHM vs no treatment, 1 (1.5%) compared CHM plus placebo vs conventional drug plus placebo, 1 (1.5%) compared CHM vs CHM plus conventional drug vs conventional drug vs placebo, and 1 (1.5%) compared CHM vs conventional drug vs CHM plus conventional drug. CONCLUSION: A variety of control groups were used in RCTs of CHM for type 2 diabetes mellitus, including placebo, active, and no treatment control groups. Justification for selecting particular types of control groups were not provided in the trials reviewed in this study. Different control groups may be appropriate according to the study objectives, and several factors should be considered prior to selecting control groups in future RCTs of CHM. RECOMMENDATIONS: (1) Investigators of CHM who design clinical trials should understand the rationale for selecting different types of control groups; (2) Control groups for RCTs should be selected according to study objectives; (3) Active control groups should select interventions for comparisons that have the strongest evidence of efficacy and prescribe them as recommended; (4) Placebo control groups should select a placebo that mimics the physical characteristics of test intervention as closely as possible and is completely inert; (5) No treatment control groups should only be used when withholding treatment is ethical and objectives outcomes will not be subject to bias due to absent blinding; (6) Crossover control groups may be appropriate in chronic and stable conditions.

Control Groups↗