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PubMed1989

Stage-related behavioural problems in the 1-4 year old child: parental expectations in a child development unit referral group compared with a control group.

Behavioural problems in preschool (1-4 years) children are a common cause of referral to health services. Parents of children presenting to the child development unit with behavioural problems (n = 18) were compared with a control group (n = 45). A questionnaire was utilized to examine the parents' expectations of the children's behaviours. As might be expected, the parents of children presenting to the Unit rated their children as having more difficult behaviours. These parents had unrealistic expectations, particularly for the 'negative' behaviours (disobedience, temper tantrums, defiance and whinging). However, they were able to anticipate normal age-related difficulties in some problem areas (dawdling during mealtimes, masturbating, not sharing toys and being jealous of one's siblings). Counselling should address the issue of matching the expectations of parents with the individual rates of development of their children.

Adult↗
PubMed1986

Intravenous clonidine treatment in acute myocardial infarction (with comparison to a nitroglycerin-treated and control group).

This study describes the effects of intravenous clonidine treatment in a group of 24 patients with acute myocardial transmural anterior and/or lateral wall infarction. Clonidine was administered as a bolus injection of 1-2 micrograms/kg body weight and repeated every 1-3 h. The range of the time of administration varied from 20 min to 4 h, with the maximal range of doses from 37 to 150 micrograms, depending on the hemodynamic status. The effects were measured by precordial electrocardiographic mapping and compared with similar effects obtained in the nitroglycerin-treated group (30 patients) and a control group (12 patients). A large decrease in ST segment elevation was observed. The ST reduction after 24 h was 37% of initial value (compared with 52% in the nitroglycerin group, 140% in the control group); after 48 h there was a 30% reduction (compared with 55% in the nitroglycerin group and 120% in the control group). After 24 h there was a fall in NST of 45% (71% with nitroglycerin and 145% in the control group); after 48 h there was a 41% decrease (compared with 65% in the nitroglycerin group and 142% in the control group). New Q waves increased after 24 h to 135% of the initial value (compared with 122% in the nitroglycerin group and 156% in the control group); after 72 h this increased to 137% (128% in the nitroglycerin group and 167% in the control group). Detailed analysis revealed a correlation between the dosage and favorable dynamics of mapping parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

Intra- and interhemispheric EEG differences quantified by spectral analysis. Comparative study of two groups of schizophrenics and a control group.

In this work we have studied comparatively the relationships between alpha intensity, alpha frequency, root-mean-square amplitude and their standard deviations, versus the location of the four recorded EEG channels: left and right rolando-parietal, left and right parieto-occipital. Twenty-four spectral parameters were computed for each 5-min EEG recording, in the eyes closed situation. The hebephrenic group (36 EEGs from six patients) presented higher values of alpha intensity and RMS amplitudes with low coefficient of variation when compared with the other groups. The left/right rolando-parietal amplitude ratio was 0.73 versus 1.52 for the parieto-occipital ratio. An amplitude hypovariability in the central regions, probably associated with hyperarousal, especially in the left hemisphere, can then be observed in hebephrenics, together with high alpha intensity on the left parieto-occipital area. The two groups of schizophrenics differ from the control group (27 EEGs from 12 subjects) in terms of spectral parameters, the hebephrenic group presenting a possible interhemispheric dysfunction.

Adult↗
PubMed2004

A pilot study of quantitative aspiration in patients with symptoms of obstructive sleep apnea: comparison to a historic control group.

OBJECTIVE: It has been shown that many healthy people aspirate secretions at night. Patients with obstructive sleep apnea (OSA) have frequent episodes of gasping at night that may predispose them to aspiration. The purpose of this study was to determine whether patients with symptoms of OSA are predisposed to pharyngeal aspiration. STUDY DESIGN: A prospective study in which patients with symptoms of OSA were compared with a historic group of normal controls by using the same methodology. METHODS: The study was offered to patients with symptoms of OSA undergoing a sleep study. The radiotracer Technicium was infused through a plastic tube placed in the nasopharynx after the patient achieved stage II sleep. A chest radionuclide scan determined the amount of material aspirated. The Wilcoxon-rank sum test was used to compare the mean amount aspirated between the experimental and historic control groups. RESULTS: Fourteen patients successfully completed the study. One normal volunteer in our study aspirated a quantity similar to the historic normal control group. The amount of aspirated material in the study group ranged from 0.152 to 3.648 mL, with a mean of 1.24 mL +/- 0.905 (SD). When compared with the historic normal control group, the patients with symptoms of OSA aspirated significantly more radio-tracer (P <.01). There was a lack of association between respiratory disturbance index and amount aspirated. CONCLUSIONS: The results suggest there is an apparent risk of increased pharyngeal aspiration in patients with symptoms of OSA.

Adult↗
PubMed2000

Placebos, active control groups, and the unpredictability paradox.

Randomized controlled trials often rely on placebo control groups to estimate treatment differences. Recently, the high frequency of negative trials and ethical concerns surrounding the use of placebos have brought the use of placebo control groups under increased scrutiny. Although many psychiatric researchers argue that placebo control groups should be replaced with active control groups, we argue that preferential use of active control groups will not reduce the number of negative trials. Rather, we suggest that some of the variation and contradiction in randomized controlled trial results arises from the clinical heterogeneity of patient characteristics, disease severity, comorbidity, and cotherapies. Further characterization of patient heterogeneity, through improved disease taxonomies, severity indices, and classification of comorbid diseases, will serve to reduce clinical heterogeneity among patients and reduce the number of negative trials produced by wide variation in treatment and control response rates.

Clinical Trials as Topic↗
PubMed2003

The use of control groups in artificial grammar learning.

Experimenters assume that participants of an experimental group have learned an artificial grammar if they classify test items with significantly higher accuracy than does a control group without training. The validity of such a comparison, however, depends on an additivity assumption: Learning is superimposed on the action of non-specific variables-for example, repetitions of letters, which modulate the performance of the experimental group and the control group to the same extent. In two experiments we were able to show that this additivity assumption does not hold. Grammaticality classifications in control groups without training (Experiments 1 and 2) depended on non-specific features. There were no such biases in the experimental groups. Control groups with training on randomized strings (Experiment 2) showed fewer biases than did control groups without training. Furthermore, we reanalysed published research and demonstrated that earlier experiments using control groups without training had produced similar biases in control group performances, bolstering the finding that using control groups without training is methodologically unsound.

Adult↗
PubMed2002

Behavioral characteristics in delusional pregnancy: a matched control group study.

OBJECTIVE: False pregnancy or delusional pregnancy, is the condition of believing one is pregnant despite factual evidence to the contrary. This is the first study to utilize a standardized mental disorder assessment tool, The Brief Psychiatric Rating Scale (BPRS) to evaluate a group of women with delusional pregnancy compared to a group of controls. METHOD: Eleven-women with delusional pregnancy (DP) were compared to a control group matched for age, race and DSM-IV psychiatric diagnosis. All patients were receiving care in a state psychiatric hospital setting. RESULTS: Compared to matched controls, women with DP had significantly higher levels of hostility (p < .05), higher rates of prescribed polypharmacy (p < .05) and a trend toward higher antipsychotic medication dosages (t = 1.48, df = 20, p = .08). These findings may be suggestive of greater resistance to treatment in women with DP. CONCLUSIONS: Biologic and psychotherapeutic treatment interventions for women with DP may need to address factors of hostility and treatment resistance. Preliminary treatment issues include selection of specific categories of psychotropic agents, as well as psychotherapies that are cognitive and lead to modification of belief paradigm.

Adult↗
PubMed1985

Chlamydia, mycoplasmas, ureaplasmas, and yeasts in the lower genital tract of females. Comparison between a group attending a venereal disease clinic and a control group.

162 women were investigated. Group I consisted of 85 women, who were partners to men with non-gonococcal urethritis (NGU) or presented macroscopic signs of cervicitis; patients who had harbored Neisseria gonorrhoeae were excluded from the study. Group II was a control group of 77 women without any complaints from the urogenital tract and with normal findings at pelvic examination. All the women were tested for infection with Chlamydia trachomatis, Mycoplasma hominis, Ureaplasma urealyticum, and Candida albicans. In group I, chlamydiae and mycoplasmas were recovered in 44% and 36%, respectively, the corresponding figures for the control group (group II) being 5% and 19%. The difference is highly significant. No such difference between the two groups was found for ureaplasmas. Sixteen percent of the patients in group I were positive for C. albicans; 12% were positive in group II. Fifty per cent of asymptomatic NGU-partners were chlamydia-positive, and about one-third of patients with either dysuria or vaginal discharge harbored the organism. No difference in the isolation frequency of mycoplasmas was observed between asymptomatic partners to male NGU carriers and women with increased vaginal discharge, whereas the organism was isolated more frequently from patients with dysuria. Fifty-nine per cent of patients with cervicitis were chlamydia-positive, compared with 30% of patients with normal cervical appearance and normal vaginal discharge. Samples obtained from the cervix were more often positive than samples from the urethra. In conclusion, if samples can be taken from only one of the two sites in patients with lower genital tract infection, the cervix is the optimal sampling site.

Adolescent↗
PubMed2005

Anterior midline point stop device (AMPS) in the treatment of myogenous TMDs: comparison with the stabilization splint and control group.

Two occlusal splints, the full-arch stabilization splint and the anterior midline point stop (AMPS) device, were evaluated for their efficiency in relieving myogenous temporomandibular disorders (TMD). One hundred and fourteen patients with myogenous TMD were distributed into 3 groups. The first group was treated with the AMPS device, the second with the stabilization splint, and the third group was the control group. Pain intensity was scored using the visual analogue scale before treatment and 1 month and 3 months after treatment. Statistical Package for the Social Sciences (SPSS, Chicago, Ill) and multiple comparisons tests were used to compare results before and after treatment and to compare the groups. The use of AMPS device in the first group resulted in a significant improvement after 1 month and 3 months (P < or = .001) and showed a 56.66% pain reduction. A significant improvement was also noticed in the second group (P = .001) with a 47.71% pain reduction. Although pain reduction percentage appeared more in the first group, this was not statistically significant. There was a highly significant difference between groups treated with both kinds of splints and the control group. It was concluded that both types of occlusal splints are beneficial to patients with myogenous TMD.

Adolescent↗
PubMed2000

Development of schoolchildren's smoking habits: questionnaire studies in intervention and control groups.

The objective of the present study was to describe the development of smoking from the sixth grade (age 12) to the eighth (age 14), for girls and for boys, and to study the effect of a simple anti-smoking intervention carried out in the sixth grade. All the roughly 2000 schoolchildren in Kronoberg County, born in 1982, completed an annual anonymous classroom questionnaire on smoking habits in the years 1994-96. In 1994, there were two visits, each lasting 80 min, by a campaigner from A Non-Smoking Generation to the 59 schools which opted for intervention, and no visits to the 21 schools which declined intervention. Before the intervention there were no differences in the frequency of smokers between the intervention group and the control group. In 2 y the proportion of smokers then rose among the girls from 1% to 12% and among the boys from 2% to 7%. Two years after the intervention, the proportion of smokers in the intervention group was approximately two-thirds of that in the control group. When the statistical analysis was based on the individual pupils, the difference between the two groups was statistically significant, but if the schools were used as the unit of analysis, the result was non-significant. Even a small-scale intervention may have an effect on the development of smoking among schoolchildren, but other preventive measures in the schools probably also contributed to the positive development of smoking in the intervention group.

Adolescent↗
PubMed2006

A comparison of the fast stimulation multifocal-ERG in patients with an IOL and control groups of different age.

PURPOSE: It has been shown that a cataract significantly reduces mfERG responses in the central 4-14 degrees . Removing the cataract, leads to a significant increase in the response of the central 4 degrees . In this study we compare the mfERG of Woerdehoff et al.'s patients' [Doc Ophthalmol 2004; 108(1): 67-75] following cataract surgery to a healthy control group in order to assess whether, in the elderly, further influences of age need to be considered in addition to optical effects. METHODS: Eighteen patients with an IOL following cataract surgery and 29 healthy volunteers (without clouding of the media or retinal changes) underwent testing of the mfERG (103 hexagons stimulating the central 50 degrees , M-sequence 2(15), Lmax: 200 cd/m2, Lmin<1 cd/m2). For the first order response component we compared the latencies of N1,P1 and N2 as well as the natural logarithm (ln) of the amplitudes N1P1 and P1N2 for four group averages: I. the central 4 degrees, II. 4-7 degrees, III. 7-10 degrees and IV. 10-15 degrees. RESULTS: Mean age was 67 years (SD 10.1) for the IOL patients, 28.5 years (SD 5.6) for a young group of controls (n=15) and 60.2 years (SD 9.2) for the older control group (n=14). Patients with an IOL did not differ in latency from either control group (ANOVA, Tukey). Interestingly, at 10-15 degrees eccentricity, the latency of N2 differed significantly between the younger (41.4 ms, SD 1.4) and the older (43.0 ms, SD 1.9) control group. In the central 4 degrees LnN1P1 amplitudes were significantly lower in the IOL group (mean: 3.7, SD 0.2) than either the younger (mean: 3.9, SD 3.3) or the older (mean: 4.0, SD 0.3) control group. In all other amplitude measures, the older control group had slightly larger mean amplitudes than the younger control group and significantly larger amplitudes than the patients with an IOL, whose amplitudes were lowest. DISCUSSION: Both, primarily optical but also neural phenomena have been described to affect the mfERG changes observed with age. Our results, are in support of this, as the improvement of the mfERG response following cataract surgery does not seem to reach the level of a healthy control group of equal age. Thus, our results suggest, that a control group with an IOL should be used when retinal function is tested in subjects with an IOL.

Adult↗
PubMed1979

[Use of the control group selected by a method of matched samples in the evaluation of the health status of children from complicated pregnancies].

A method of matched samples consisting in selection of "a partner" for each examined individual according to the established criteria of similarities is one of the methods used owing to its apparent organizational ease in selecting of the control group. The control group selected in this way was used in the evaluation of the effect of bleeding during the first 16 weeks of pregnancy on the health status and physical development of children. The paper points out the advantages of using the control group selected by the method of matched samples. It also presents the difficulties encountered in practice. Typical of this study technical methods and statistical tests used in evaluation of the results were juxtaposed and discussed, then compared to those used when a group was randomly selected. Special attention was paid to 3 basic problems: Time stability is selection of criteria for matched samples. Adjustment of age differences within pairs. Two methods were used for comparison of the anthropometric measurements. The first one consisted in levelling of the differences by the method of regression, the second in the use of various available growth curves. The results obtained by both methods were compared by means of statistical tests. The third problem concerned adequacy of the tests used when the control group was selected by the method of matched samples. Results obtained by application of t-Student test for paired samples were compared to those obtained by t-Student test for independent variables. The merits of the method of matched samples were presented using some examples (table I, II, III). Eleven conclusions were drawn from evaluation of suitability of selecting the control group according to the method of paired samples. These can be put into three main groups: Showing in what kind of studies the control group selected by the method of matched samples is payable . Showing various inconveniences caused by selection of the control group by the method of matched samples, Conclusions concerning methodological or other benefits drawn from this method. It is clearly indicated in this paper that the control group selected by the method of matched samples is recommended only in certain investigations. Before the final decision is taken all pros and cons should be considered.

Anthropometry↗
PubMed2005

Importance of control group selection for evaluating antimicrobial use as a risk factor for methicillin-resistant Staphylococcus aureus bacteremia.

OBJECTIVE: We investigated the importance of control group selection during an evaluation of antimicrobial use as a risk factor for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia at our institution. METHODS: We performed a case-control study. A case was defined as any patient admitted between January 1997 and May 2001 who developed nosocomial MRSA bacteremia. We used two control groups; control group I consisted of patients with nosocomial methicillin-susceptible S. aureus (MSSA) bacteremia and control group II included only patients without bacteremia. We matched control-patients to case-patients using age, gender, time at risk, and hospital ward. Data collected on all patients included demographics, comorbidities, antibiotic use, time at risk, length of stay, severity of illness, and outcome. RESULTS: We evaluated 63 patients (21 in each group). The three groups were well matched regarding age, gender, underlying diseases, and severity of illness. Patients in the MRSA group were more likely to have received a fluoroquinolone and had a higher mean number of days of fluoroquinolone use than did patients in the MSSA group (P = .027 and P = .015, respectively). However, all measures of fluoroquinolone use were similar for case-patients and for control-patients who did not have nosocomial bloodstream infection. CONCLUSIONS: Control group selection is important in evaluating antimicrobial use as a risk factor for MRSA bacteremia. Using control-patients infected with MSSA, rather than uninfected control-patients, may overestimate the association between antimicrobial use and MRSA infection.

Anti-Bacterial Agents↗
PubMed1990

[Four-week training of patients with large anterior wall infarct: comparison with a randomized untrained control group].

Thirty-nine male patients (average age 50.8 years +/- 8.4 years) with a large anterior myocardial infarction (average 45.6 days +/- 10.5 days ago) and with moderate to severe left-ventricular dysfunction (RNVA EF less than 50%) participated in the study. The patients were randomly assigned to either a training group or to a control group. They were also subdivided into training/control groups (EF less than 30% and EF = 30-50%). The training program consisted of three to four sessions per day, 5 days a week, at an intensity of up to 1 W/kg body wt. (approximately 4-5 METS). The following evaluations were recorded prior to and following the 4-week training program: relative heart volume (x-ray), echocardiographic data (enddiastolic diameter, ES-distance, and shortening fraction), and exercise stress test (work capacity, heart rate). Filling pressures, cardiac outpout, and stroke volume index were calculated from right-heart catheterization (Swan-Ganz) at rest and during exercise. Results indicate that there were no significant changes in relative heart volume, end-diastolic volume, ES-distance, resting heart rate, PCP at rest, and ejection fraction during exercise as a result of the training program. Shortening fraction showed a tendency to improve (not significant). Work capacity increased by 15 W (p less than 0.05) in the training group and by 28 W (1.5 METS, p less than 0.05) in the EF less than 30% training-group as compared with the control group. Cardiac output at rest decreased by 10% (p less than 0.05). Stroke-volume index increased in the EF greater than 30% training-group, while heart rate was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMed2000

[Roaming through methodology. XVIII. Selection of control groups].

The selection of a valid control group is important in case control studies and has therefore generated a fair amount of discussion in the epidemiologic literature. The proposal of the study usually determines the type of control group that should be selected. It is possible to select population controls, hospital controls, friends or relatives of patients or a variant of these. Each method has specific advantages and disadvantages. Random-digit dialing can be used to select population controls by telephone. This method is a valuable alternative when no registry exists.

Case-Control Studies↗
PubMed1995

Selecting control groups for studies of familial aggregation of disease.

In genetic-epidemiologic studies to determine the association between the disease status of family members, this association is measured by comparing rates of the disease in relatives of probands (index cases) with the disease, with the rates of the disease among individuals in a control group. Either of two types of control groups are generally used: (1) a control group consisting of a random sample from the population or the entire population if available or (2) a control group consisting of relatives of individuals without the disease under study. We examine the advantages and disadvantages of using these different types of control groups. We show two major results for family studies: (1) when there are no other factors associated with the disease status of an individual other than the disease status of a family member, both types of control groups will give a valid test of the null hypothesis of no familial aggregation. However, tests using a population control group will always be less efficient statistically, than those performed with a control group of relatives of probands without the disease under study, the degree of efficiency decreasing with increasing population prevalence of the disease. (2) When factors other than the disease status of a family member are also associated with the disease status of an individual, if this factor is a proband characteristic (which is not shared by relatives) population control groups cannot be adjusted to eliminate possible bias due to the potential confounding effect of this factor (unlike control groups consisting of relatives of probands without the disorder).

Bias↗