Multifactorial aspects to explain variations of control group mortality rates of randomized controlled trials.
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Causality↗
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Control of selection bias in parallel-group controlled clinical trials in dogs and cats: 97 trials (2000-2005).
OBJECTIVE: To determine how selection bias (allocation bias) was controlled in published clinical trials. DESIGN: Retrospective study. SAMPLE POPULATION: 97 parallel-group controlled clinical trials published from January 2000 through December 2005 in 12 peer-reviewed journals. PROCEDURES: Journals were hand searched to identify eligible reports. Details concerning allocation of animals to study groups, baseline characteristics of the groups, and the number of animals allocated to each group were recorded. RESULTS: Randomization was the stated method of allocating animals to groups in 87% of the reports, yet in only 11% of reports were both randomization of the group allocation process and concealment of the allocation sequence described. Studies reported as randomized were more likely to report baseline characteristics of the study groups for comparison than studies that did not report randomization (88% vs 54%). Studies in which baseline group characteristics were reported had more subjects allocated to each study group (median, 16) than those that did not (median, 11). CONCLUSIONS AND CLINICAL RELEVANCE: Randomization was reported as the method of allocating study animals to groups in most publications, indicating that the potential power of randomization in controlling selection bias is appreciated by clinical investigators seeking to determine the efficacy of an intervention. However, in most reports, little corroborating information was included to support the claim. The absence of this information makes it difficult for practitioners to critically review the impact of bias on study results and make informed decisions regarding patients.
Animals↗
Carcinogenicity evaluation: comparison of tumor data from dual control groups in the Sprague-Dawley rat.
Following recent clarification in Europe that a single control group is now acceptable for rodent carcinogenicity studies, the use of dual controls may be reduced or disappear. To date, virtually nothing has been published on whether this latter situation has improved the identification of tumorigenic risk potential in these studies. In this paper, the results of 13 rat carcinogenicity studies, performed between 1991 and 2002, with 2 control groups, are presented. Although no major differences in tumor incidences between these dual control groups were found, some interstudy variation occurred. In cases where a notable difference was seen, the use of 2 control groups, as well as robust, contemporary background data, allowed an easier interpretation of findings in drug-treated groups. Thus, the continued use of dual control groups has a vital role in the assessment of tumoriogenic risk. The paper also presents an update on survival, on the range and extent of background spontaneous neoplasms, and comments on genetic drift in this commonly used rat strain.
Animals↗
Randomized controlled trials: the control group dilemma revisited.
In some randomised controlled trials the nature of the therapy means that subjects cannot or should not be blinded. Such studies need careful design. Particular attention needs to be given to the choice of control group and the nature of the informed consent obtained from subjects, because these affect the precise research question being addressed. A survey of published studies was carried to investigate how these issues had been tackled. The paper summarizes key findings from the survey. If the research question is about the specific effect of a therapy sometimes a good case can be made for a second control group which is 'attention-controlled'. There is a need for more detailed justifications of such design decisions in published studies.
Complementary Therapies↗
On choosing the control group in case-control studies.
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Epidemiologic Methods↗
The validity of different control groups in a case-control study. Oral contraceptive use and breast cancer in young women.
The possible selection bias due to the use of different series of controls in case-control studies has been analysed in the Norwegian part of a joint national case-control study in Sweden and Norway of oral contraceptive (OC) use and breast cancer in young women. A total of 105 cases diagnosed 1984-1985 were interviewed in addition to 210 population controls matched for age, 104 neighbourhood controls matched for age and postal address, and 96 hospitals controls matched for age. The relative risk was for each of the sets of controls 1.0 for 8 years and more of total use of OCs (adjusted for age at menarche, parity, age at first full term pregnancy, history of breast cancer in mother, history of benign breast biopsy). An additional questionnaire was sent to those who did not wish to participate (non-attenders). A slight selection bias was found for the population controls with more nulliparous never-users of OCs among the non-attenders than among interviewed controls.
Adult↗
Hepatitis cases in isoniazid treated groups and in a control group.
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Adult↗
[Choice of control group in case-control studies].
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Case-Control Studies↗
White matter lesions in patients with idiopathic normal pressure hydrocephalus and in an age-matched control group: a comparative study.
OBJECTIVE: To compare the occurrence of periventricular lesions (PVLs) and deep white matter lesions (DWMLs) in elderly patients with idiopathic normal pressure hydrocephalus (NPH) and in an age-matched control group. METHODS: PVLs and DWMLs were evaluated using T2-weighted magnetic resonance scans of 37 patients with idiopathic NPH and 35 participants from an age-matched control group. All patients with idiopathic NPH included in this study improved after shunting. The control group consisted of 16 healthy elderly persons and 19 patients with depression. To allow quantitative assessment and comparison, scores for PVLs and DWMLs were calculated. Furthermore, possible correlations between white matter lesion scores, ventricular width, and age were investigated. RESULTS: There was a significantly higher incidence of PVLs and DWMLs in patients with idiopathic NPH. The mean total PVL was 12.1 (range, 2-24) in the NPH group and 3.9 (range, 0-10) in the control group (P < 0.001). The mean total DWML score was 12.9 (range, 3-24) in the NPH group and 4.5 (range, 0-16) in the control group (P < 0.001). There were significant correlations between the severity of PVL and DWML scores in both groups. Only a weak positive correlation between the severity of DWMLs and age was found in the NPH group, whereas this correlation was significant in the control group. There was a significant negative correlation between the width of the anterior horns and the severity of both PVLs and DWMLs in patients with NPH; however, positive correlations were found in the control group. CONCLUSION: Elderly patients with idiopathic NPH have more frequent and more severe PVLs and DWMLs than people in age-matched control groups. Our data suggest a frequent co-occurrence of idiopathic NPH and vascular subcortical encephalopathy; however, they do not support a direct causal relationship.
Aged↗
A multicentre comparative study of serum lipids and lipoproteins in four groups of oral combined contraceptive users and a control group of IUD users. World Health Organization. Task Force on Oral Contraceptives.
A prospective clinical trial was conducted in three centres to assess the effects of the type and dose of progestogen, the dose of estrogen and the progestogen-to-estrogen ratio of oral contraceptives on lipid metabolism. The preparations selected contained levonorgestrel 250 micrograms + ethinyl estradiol 50 micrograms (Neogynon), levonorgestrel 250 micrograms + ethinyl estradiol 30 micrograms (Eugynon 30), levonorgestrel 150 micrograms + ethinyl estradiol 30 micrograms (Microgynon) or norethisterone acetate 1 mg + ethinyl estradiol 50 micrograms (Minovlar). Four-hundred-and-seven premenopausal women were randomly assigned to one of the four pill groups and compared to a control group of 119 users of a CuT220c intrauterine device. Total cholesterol, HDL-cholesterol, LDL-cholesterol and total triglycerides were monitored and the analysis includes the data of those who were followed over 48 weeks, 241 OC users and 87 IUD users. 250 micrograms of levonorgestrel were found to induce more unfavourable lipid changes in terms of atherosclerotic risk than 1mg of norethisterone acetate. Levonorgestrel was found to have a dose-effect on HDL-cholesterol and LDL-cholesterol serum levels, while ethinyl estradiol had a dose-effect on serum triglycerides. HDL-cholesterol was related to the progestogen-to-estrogen ratio. Most of these findings were consistent across centres. Finally, some comments are made on the implications of the study results on the design of future lipid studies.
Adolescent↗
Surgical treatment of atrial fibrillation through isolation of the left atrial posterior wall in patients with chronic rheumatic mitral valve disease. A randomized study with control group.
OBJECTIVE: To determine the effectiveness of surgical isolation of the left atrial posterior wall encompassing the ostia of the pulmonary veins for the treatment of atrial fibrillation of rheumatic etiology. METHODS: Prospective and randomized study of patients with rheumatic mitral valve disease, persistent atrial fibrillation for 6 months or longer, age < or = 60 years, and left atrial diameter < or = 65 mm. The patients were randomly distributed into 2 groups as follows: surgical valvular treatment (control group) and surgical valvular treatment associated with isolation of the left atrial posterior wall according to the "cut-and-sew" technique (treated group). RESULTS: Twenty-nine individuals were operated upon, 27 of whom (13 in the control group and 14 in the treated group) were regularly followed up. The patients of both groups did not differ in regard to their basal characteristics. The mean follow-up time was 11.5 months in the control group and 10.3 months in the treated group. The cumulative frequencies of the patients without atrial fibrillation were significantly greater in the treated group both in the perioperative (P = 0.0035) and late (P = 0.0430) phases. CONCLUSION: Surgical isolation of the left atrial posterior wall encompassing the ostia of the pulmonary veins is an effective form of treating atrial fibrillation in rheumatic mitral valve disease.
Aged↗
Healthy sleepers are rare: problems and success rates in establishing a control group for sleep studies.
A large and representative control group is paramount for establishing normative values for sleep in middle-aged persons. However, it is very difficult to recruit normal sleepers. From 286 volunteers who responded to an advertisement for healthy sleepers, only 47 finished the study. We excluded 221 after evaluation of their medical sleep history, general health data, and results of physical examination. We further excluded 18 volunteers after nighttime polysomnography. We finally eliminated from the study 37.5% of the volunteers who entered the screening procedure, on grounds of their sleep disturbances. Our study reveals that investigators face major difficulties when trying to establish a control group of healthy sleepers from the middle-aged population. Sufficient interest on the part of potential test persons does in fact exist, but their general health-and, especially, previously undiscovered sleep disorders-frequently prohibit their inclusion. International and interdisciplinary cooperation is necessary to establish a sufficiently large control group for both clinical and research purposes.
Adult↗
Evaluating the impact of a disease management program for chronic complex conditions at two large northeast health plans using a control group methodology.
The objective of this study was to observe trends in payer expenditures for plan members with one of 14 chronic, complex conditions comparing one group with a disease management program specific to their condition (the intervention group) and the other with no specific disease management program (the control group) for these conditions. The authors used payer claims and membership data to identify members eligible for the program in a 12-month baseline year (October 2001 to September 2002) and a subsequent 12-month program year (October 2002 to September 2003). Two payers were analyzed: one health plan with members primarily in New Jersey (AmeriHealth New Jersey [AHNJ]), where the disease management program was offered, and one affiliated large plan with members primarily in the metro Philadelphia area, where the program was not offered. The claims payment policy for both plans is identical. Intervention and control groups were analyzed for equivalence. The analysis was conducted in both groups over identical time periods. The intervention group showed statistically significant (p < 0.01) differences in total paid claims trend and expenditures when compared to the control group. Intervention group members showed a reduction in expenditures of -8%, while control group members showed an increase of +10% over identical time periods. Subsequent analyses controlling for outliers and product lines served to confirm the overall results. The disease management program is likely responsible for the observed difference between the intervention and control group results. A well-designed, targeted disease management program offered by a motivated, supportive health plan can play an important role in cost improvement strategies for members with complex, chronic conditions.
Case-Control Studies↗
Visual and somatosensory event-related brain potentials in autistic children and three different control groups.
Event-related potentials (ERPs) to visual and somatosensory stimuli, generated during an oddball task, were obtained in a group of autistic children and 3 control groups (normal, attention-deficit, and dyslectic children, respectively). The task included the presentation of standard, deviant, and novel stimuli and had a (between-group) passive vs. active (counting) condition. Research questions were whether (a) autistic children differ from other children with respect to the processing of visual and/or somatosensory stimuli, as measured in the amplitude of the N1, mismatch activity, and P3, (b) autistic children specifically have problems in the processing of distal (visual) stimuli, compared to the processing of proximal (somatosensory) stimuli, and (c) autistic children have an atypical lateralization pattern of ERP activity. Only in the autistic group a task effect on the visual P2N2 (mismatch activity) and larger P3s to novels than to deviants were found, in both the visual and the somatosensory modality. There also was a smaller occipital P3 to visual standard stimuli in the passive condition in the autistic group than in 2 control groups. We concluded that autistics (a) differ from several other groups of children with respect to the visual P2N2 and the visual and somatosensory P3, (b) show abnormalities in the processing of both proximal and distal stimuli, and (c) show no indication of abnormal lateralization of ERPs.
Adolescent↗
Neurodynamic responses in children with migraine or cervicogenic headache versus a control group. A comparative study.
Headache in children with unknown aetiology is an increasing phenomenon in industrial countries, especially during growth spurts. During this growth phase, the Long Sitting Slump (LSS) can be a useful tool for measurement of neurodynamics and management. This study investigated the difference in cervical flexion and sensory responses (intensity and location) during the LSS tests in children (n=123) aged 6-12 years, between a migraine (primary headache group=PG), cervicogenic headache (secondary headache group=SG) and control group (CG). The results indicated that the intensities of the sensory response rate were highest in the PG and SG when compared to CG. The responses in the legs were predominantly found in the PG (81.9%) and responses in the spine in the SG (80%). The sacrum position varied significantly between both headache groups (PG and SG) and the CG (p<0.0001), but there was no significant difference between the CG and the PG (p>0.05). No significant difference in the neck flexion range was measured in LSS, nor in standardized knee flexion between the PG and CG (p>0.05). The cervical flexion ranges differed significantly (p<0.0001) between the SG on the one hand and the PG and CG on the other. The biggest difference in neck flexion during knee extension was between the SG and CG.
Case-Control Studies↗
Effects of intravenous cibenzoline on ventricular vulnerability and electrophysiology in patients with sustained ventricular tachycardia in comparison to a control group.
The electrophysiologic effects of intravenous (i.v. 1.5 mg/kg) cibenzoline were investigated in 13 patients with organic heart disease and supraventricular arrhythmias (control group) and 13 patients with drug refractory sustained ventricular tachycardia (VT group). In both groups, cibenzoline increased the effective refractory period (ERP) of the right ventricle (p less than or equal to 0.05), QRS duration (p less than or equal to 0.01), and QTc duration (p less than or equal to 0.01). Cycle length of the VT was increased from 311 +/- 73 to 393 +/- 119 ms (p less than or equal to 0.05) as well. The increase in QTc duration was more pronounced (p less than or equal to 0.05) in the VT group as compared with the control group. In four patients in the VT group with the largest increase in QRS-, QTc duration and cycle length of the VT proarrhythmia was noted after i.v. cibenzoline. Cibenzoline plasma levels were not significantly different between the two study groups. In the VT group, induction of VT was prevented in 2 patients, more difficult in 2 patients, easier in 1 patient, and unchanged in 5 patients. Spontaneous occurrence of the VT or induction by atrial stimulation was noted in 4 patients. In the control group, ventricular vulnerability remained unchanged. Cibenzoline may be effective in selected patients with drug refractory VT. In such patients, the increase in QTc duration was more pronounced as compared with a control group.
Anti-Arrhythmia Agents↗
Does a joint development and dissemination of multidisciplinary guidelines improve prescribing behaviour: a pre/post study with concurrent control group and a randomised trial.
BACKGROUND: It is difficult to keep control over prescribing behaviour in general practices. The purpose of this study was to assess the effects of a dissemination strategy of multidisciplinary guidelines on the volume of drug prescribing. METHODS: The study included two designs, a quasi-experimental pre/post study with concurrent control group and a random sample of GPs within the intervention group. The intervention area with 53 GPs was compared with a control group of 54 randomly selected GPs in the south and centre of the Netherlands. Additionally, a randomisation was executed in the intervention group to create two arms with 27 GPs who were more intensively involved in the development of the guideline and 26 GPs in the control group. A multidisciplinary committee developed prescription guidelines. Subsequently these guidelines were disseminated to all GPs in the intervention region. Additional effects were studied in the subgroup trial in which GPs were invited to be more intensively involved in the guideline development procedure. The guidelines contained 14 recommendations on antibiotics, asthma/COPD drugs and cholesterol drugs. The main outcome measures were prescription data of a three-year period (one year before and 2 years after guideline dissemination) and proportion of change according to recommendations. RESULTS: Significant short-term improvements were seen for one recommendation: mupirocin. Long-term changes were found for cholesterol drug prescriptions. No additional changes were seen for the randomised controlled study in the subgroup. GPs did not take up the invitation for involvement. CONCLUSION: Disseminating multidisciplinary guidelines that were developed within a region, has no clear effect on prescribing behaviour even though GPs and specialists were involved more intensively in their development. Apparently, more effort is needed to bring about change.
Adult↗
Yearling trait comparisons among inbred lines and selected noninbred and randomly bred control groups of Rambouillet, Targhee and Columbia ewes.
Inbreeding with concurrent selection was used to develop 26 Rambouillet, 20 Targhee and 10 Columbia inbred lines of sheep. Inbreeding coefficients averaged 30, 29 and 30% for the three breeds, respectively, at the conclusion of the study. A selected noninbred control group and a randomly bred unselected control group were maintained for each breed. Yearling traits were evaluated for 545 Rambouillet, 572 Targhee and 411 Columbia yearling ewes, each belonging to one of the inbred lines or control groups. In each breed, the selected controls were generally of greatest overall merit, the unselected controls intermediate and the inbred lines of least merit. Only a few yearling traits of only a few inbred lines were superior (P less than .05) to those of their appropriate selected control groups. Selection within inbred lines was generally ineffective in offsetting inbreeding depression. However, single trait selection for traits of high heritability, notably yearling weight, clean fleece weight and staple length, appeared to compensate for inbreeding effects on those traits. Deleterious consequences of inbreeding were particularly apparent in yearling weight, average daily gain, type and condition scores, grease and clean fleece weights and index of overall merit. Inbreeding also resulted in fewer neck folds among inbreds of all three breeds. Correlations between the rankings of inbred lines at weaning and yearling ages were high for traits of higher heritability. Superiority of the selected controls in most traits was of about the same magnitude at weaning and yearling ages. In no case did the final overall merit (index value) of an inbred line of any of the three breeds significantly exceed the overall merit of its respective selected control group.
Age Factors↗