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Results for “Internal validation”

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At least 757 records · Page 42Linked to original sources

PubMed1986

How blind is blind? Assessment of patient and doctor medication guesses in a placebo-controlled trial of imipramine and phenelzine.

The purpose of the double blind is to protect the internal validity of a clinical trial by preventing knowledge of treatment conditions from influencing outcome or its assessment. We studied medication guesses of 137 depressed patients and/or their doctors at the end of a 6-week randomized trial of placebo, imipramine, and phenelzine. Overall, 78% of the patients and 87% of the doctors correctly distinguished between placebo and active medication. Clinical outcome, treatment condition, and their interaction each contributed to guessing accuracy, while medication experience and side effects assessed only in week 6 did not. Accuracy was high, however, even when cases were stratified for clinical outcome, indicating that other cues were available to the patients and doctors. These may include patterns and timing of side effects and clinical response not detectable in this end-point analysis.

Adolescent↗

PubMed1991

Issues for comparability of DRG statistics in Europe. Results from EURODRG.

DRG use has spread through most European countries thus offering an opportunity for improving hospital data bases at the European level. An EEC Concerted Action 'Use of DRGs to support Hospital Sector Management in the European Community' was approved by the Committee of Health Services Research of the EEC. A general overview of the project is presented as well as a detailed description of the results of the work on aspects related to DRG data production. These aspects (MBDS implementation and variables definition; coding systems and updating; mapping systems; data auditing; trimming methods; and DRG grouper versions) have been analyzed with the objective of increasing opportunities for valid international comparisons of DRG statistics between European countries.

Abstracting and Indexing↗

PubMed1985

The FRAME interlaboratory programme on in vitro cytotoxicology.

FRAME (the Fund for the Replacement of Animals in Medical Experiments) has established a research programme in collaboration with four research centres and a number of industrial companies, to determine whether cell cultures can reliably be used to replace live animal procedures in routine tests on the relative acute toxicities of chemicals. Following the development of the test protocol, initial trials were carried out to establish intralaboratory and interlaboratory reproducibility and the criteria for choice of cell types, end-points and metabolizing systems. A set of coded chemicals is being collected for use in blind trials and summaries of existing knowledge of the in vivo toxicity of these compounds are being produced. More recently, FRAME has established an international validation scheme for in vitro alternative methods.

Animal Testing Alternatives↗

PubMed1992

Statistical evaluation of the fixed-dose procedure.

The fixed-dose procedure (FDP) was proposed by the British Toxicology Society in 1984 as an alternative to the LD50 study in the assessment of the acute oral toxicity of a substance. This paper presents a statistical evaluation of this procedure. A mathematical description of the FDP shows that the starting dose can affect the toxic classification of a substance. The toxic classification based on the FDP is compared with that based on an LD50 test. This shows that, in general, the FDP is likely to result in the same classification or a less toxic one than the LD50 procedure. However, for substances with very shallow dose-response slopes, the FDP is likely to result in the same classification or a more toxic one. The expected number of animals that will be tested and will die using the FDP will be reduced compared with the LD50 study. The results from the international validation study carried out in 1989 showed agreement with the results predicted from the mathematical model.

Animals↗

PubMed1987

Stages of adolescent cigarette smoking acquisition: measurement and sample profiles.

A stage model of adolescent cigarette smoking acquisition was developed and an instrument to measure the stages was created. Internal validity was obtained based on principal component analysis, item analysis, and coefficient alpha. Three distinct components were labeled precontemplation, decision-making, and maintenance. The scales had reliability coefficients ranging from .86 to .94. External validity was obtained by relating the scale scores to measures of smoking behavior and intent to smoke. A cluster analysis resulted in nine distinct clusters, including profiles representing precontemplation, contemplation, decision-making, action, and maintenance stages. Further validity was obtained for the clusters by comparing groups on the perceived positive and negative consequences of smoking, and the derived pleasure from smoking.

Adolescent↗

PubMedDate not supplied

The cast-6: development of a short-form of the Children of Alcoholics Screening Test.

The 30-item Children of Alcoholics Screening Test (CAST) is shortened to a 6-item scale (CAST-6) using Principal Components Analysis of CAST responses for three distinct samples: outpatient substance abusers, outpatient psychiatric patients, and medical students. The face validity, internal consistency, and discriminatory ability of the CAST-6 are examined. The CAST-6 is judged to compare favorably with the full CAST and to provide a more efficient way to identify adult children of alcoholics.

Adult↗

PubMed1989

Is the published literature a reliable guide for deciding between alternative treatments for patients with early cervical cancer?

The quality of the methodology and reporting of studies on the treatment of early cervical cancer published in English and French language over the period 1975-1985 were examined using an explicit, pre-defined protocol aimed at assessing their internal validity and generalizability. One hundred and fifty-two articles reporting results on over 40,000 patients treated with surgery, radiotherapy, or the combination of the two, were examined. The astonishing lack of formal comparative studies together with the poor quality of those actually carried out were the two major findings of our study. More than half of the reviewed papers (54%) were single series studies. Among the remaining 46% only a few formally compared the two treatments (i.e. surgery vs. radiotherapy), the remainder dealing with comparisons of specific surgical or radiotherapeutic techniques. With reference to study quality, the existence of a pre-specified research protocol could not be ascertained in most studies. A description of patients' characteristics and information on the source population were deficient in most papers reviewed; information on the two aspects was in fact satisfactorily reported in only 7% and 47% of the papers, respectively. Finally, the lack of standardization of follow-up methods (i.e. type and modalities) and of information on treatment compliance were two other severe methodological deficiencies. In view of this poor quality and of the intrinsic difficulty of drawing firm scientific conclusions from non-experimental investigations, the reliability of this literature remains highly dubious. Another possible caveat is that what is published is a biased sample of the overall evidence because of the well known tendency of authors to write about and editors to publish positive results more frequently than negative ones.

Clinical Trials as Topic↗

PubMed1995

Ocular globe topography in radiotherapy.

PURPOSE: Ocular lens, retina, and olfactory bulb exposure are common concerns in contemporary radiotherapy practice. Methods to clinically localize soft tissue structures (i.e., lens and retina) are varied and often imprecise. We hypothesized that eyelid markers constituted a better reference point than the commonly used lateral canthus marker for lateral beam simulations, unless diagnostic computed tomography or ultrasound examinations were available and/or used. METHODS AND MATERIALS: Sixty-six pre-Magnetic Resonance Image, normal, orbital computed tomography scans from adult patients were used to measure (a) sagittal distances from eyelid to posterior lens surface, from lateral canthus to posterior lens surface and to the globe's posterior pole, (b) supero-inferior distances in the lateral projection from the lens to the cribriform plate, and (c) common dimensions to establish internal validity of the measurements. RESULTS: The eyelid to lens and retina topography is individually more constant than that from the canthus. There is little if any supero-inferior separation between the lens and the cribriform plate lateral projections. CONCLUSIONS: The lateral canthus does not specify lens or retina locations. Eyelid markers of known size provide more accurate anatomical information. Lateral beam ocular globe shielding has to be individualized. Lens shielding is questionable if the olfactory bulb needs to be irradiated by a lateral beam.

Adult↗

PubMed1981

Limitations of scalogram analysis as a method for investigating drug use behavior.

Scalogram analysis, a procedure developed for constructing attitude scales, has been recently applied to support certain conclusions about the typical development of drug use patterns. An examination of results from these applications revealed at least three potential limitations: (1) presumed drug usage patterns may not generalize to many drug users, especially adult users; (2) presumed patterns may not be supported if several commonly used psychoactive substances are included; and (3) measures of unidimensionality may not be sufficient for confirming actual unidimensionality of highly skewed drug use patterns. Therefore, the present study was designed to investigate further these potential limitations and to determine their bearing upon previous theoretical conclusions. Results confirmed the existence of all three limitations. In other words, typical applications of scalogram analysis based upon adolescent illicit drug use data have questionable external and internal validity. Therefore, previous conclusions based upon such applications should be re-evaluated and future research should employ alternative analytical procedures.

Adolescent↗

PubMed1994

The cytotoxicity of 50 chemicals from the MEIC study determined by growth inhibition of ascites sarcoma BP8 cells: a comparison with acute toxicity data in man and rodents.

In this study, 50 chemicals selected on the basis of existence of particularly reliable human toxicity data were screened in a cytotoxicity test involving inhibition of the growth of Ascites Sarcoma BP8 cells. These test results are part of an international validation program, the Multicenter Evaluation of In Vitro Cytotoxicity (MEIC), the aim of which is to recommend batteries of in vitro tests to be used for prediction of human toxicity. The cytotoxicities (expressed as the concentrations causing 50% inhibition of cell growth) were compared to acute toxicity data in humans (LDL0) and rodents (LD50), showing the best correlation to rodent data. The results are discussed in relationship to what is usually referred to as basal cytotoxic mechanisms as a cause of in vivo toxicity. It could be concluded that the predicted results on the basis of mechanistic reasoning were not always obtained.

Animals↗

PubMed1994

Etest for routine clinical antimicrobial susceptibility testing of rapid-growing mycobacteria isolates.

The Etest has become a widely accepted alternative susceptibility-testing method for difficult-to-assess organisms, including rapid-growing Mycobacterium spp. Following an internal validation and literature reviews, the Etest was applied as the routine method for testing Mycobacterium chelonae and Mycobacterium fortuitum isolates. Results from testing 31 strains confirmed the utility of the Etest and the simplicity of the procedure. Mycobacterium chelonae were generally more resistant to all drugs except amikacin (MIC90, 32 micrograms/ml), compared with M. fortuitum strains that were inhibited (MIC50 in the susceptible range) by amikacin (1 microgram/ml), ciprofloxacin (0.032 microgram/ml), doxycycline (0.125 microgram/ml), and trimethoprim-sulfamethoxazole (0.032 microgram/ml). The polymyxin-B disk used as an identification method was confirmed (> or = 10 mm = M. fortuitum). The Etest provides a simple and accurate method for selecting appropriate therapy for infections caused by rapid-growing mycobacteria (a typical case report is presented).

Amikacin↗

PubMed1992

Effects of psychoeducational care for adult surgical patients: a meta-analysis of 191 studies.

A quantitative review of the literature (meta-analysis) was conducted with 191 studies of the effects of psychoeducational care on the recovery, postsurgical pain and psychological distress of adult surgical patients. Studies issued between 1963 and 1989 were included in the review. Statistically reliable, small to moderate sized beneficial effects were found on recovery, postoperative pain and psychological distress. In further analyses it was shown that these beneficial effects were not an artifact of the biases associated with the decision whether to publish a paper, low internal validity, measurement subjectivity, or a Hawthorne effect. The overall efficacy of psychoeducational care provided to adult surgical patients has been reconfirmed with this larger sample of studies. It is particularly noteworthy that these findings are of more than strictly historical interest. Despite changes in health care delivery, beneficial effects continue even in studies issued between 1985 and 1989. Implications for clinical practice are drawn.

Adult↗

PubMed1991

Researching and evaluating model geriatric mental health programs, Part I: Design of mental health evaluation studies.

The first article in this three-part series on researching and evaluating geriatric mental health programs focuses on issues related to the design of studies for summative evaluations of geriatric mental health programs. Experimental and quasi-experimental designs are discussed in terms of their advantages and disadvantages, and threats to internal validity are highlighted.

Aged↗

PubMed1987

Oddity performance in preschool children at risk for mental retardation: transfer and maintenance.

The oddity performance of five preschool children at risk for mental retardation was facilitated by increasing the number of nonodd elements in a visual array. A combination intrasubject reversal and multiple baseline across subjects design indicated the internal validity of interventions designed to enhance the perceptual salience and consequent stimulus control of the odd stimulus. Results demonstrate that transfer and maintenance of oddity learning can be obtained even with individuals for whom correct oddity responding is uncommon. The typically poor performance of young and developmentally delayed children as compared to nondelayed children on tasks such as the oddity task may be attributable to a lower sensitivity to relational information.

Attention↗

PubMed1991

The Toronto Breast Self-Examination Instrument (TBSEI): its development and reliability and validity data.

The Toronto Breast Self-Examination Instrument (TBSEI) was developed out of the need for a self-administered survey that is reliable and valid. This article describes the development of the TBSEI, its dimensions, and reliability and validity data to support its continued use. To analyze the reliability and validity properties of the three TBSEI scales, we surveyed 729 Toronto, Ontario women. The TBSEI was found to have good face and content validity, internal consistency reliability (0.91, 0.69, 0.85), and test-retest reliability (0.89). Age norms for each of the three scales are also provided. These results are consistent with previous research findings in breast cancer and breast self-examination research.

Adult↗

PubMed1994

Patterns of academic competence in adults with epilepsy: a cluster analytic study.

Cluster analysis was used in the attempt to derive a meaningful taxonomy of academic competence in 117 adults with temporal lobe epilepsy. Reading, spelling and arithmetic achievement scores from the Wide Range Achievement Test-Revised were subjected to hierarchical complete linkage cluster analysis, and the stability of the obtained solution was examined by the application of two additional clustering procedures. A six cluster solution was obtained, and tests of internal validity showed membership in four of the clusters to be extremely stable (Moderate and Marked Reading/Spelling Underachievement, Above Average Achievement, Reading/Arithmetic Underachievement), while the remaining two clusters showed some exchange of cases (Arithmetic Underachievement, Average Achievement). Modest evidence of external validity was found through the comparison of specific clusters to the Average Achievement group on measures of neuropsychological function, neurological and demographic characteristics. It is concluded that cluster analysis may be helpful in developing taxonomies of psychosocial impairment in epilepsy, and may facilitate an understanding of the determinants of variable quality of life outcomes associated with epilepsy.

Adult↗

PubMed1996

Quality of prostate cancer data in the cancer registry of Norway.

Completeness of reporting and internal validity of the coding of prostate cancer in the Cancer Registry (CR) in Norway were examined. Data were matched and evaluated against diagnostic indices at eight selected hospitals in the country and against death certificates from Statistics Norway. Validity control was based on detailed re-analysis of an approximately 1% sample of the registered data during the period 1957-1986. The deficiency in reporting of prostate cancer was less than 1%. The grave deficiencies in hospital patient registers were considered to be of non-systematic nature and should, therefore, not impair the reliability of our investigation of incompleteness. The validity control revealed errors in 0.5% of the data elements, or, illustrated differently, 6% of the patient files had an error, of importance or not, in one of the data elements. One false positive registration was found among 298 controlled patient files (0.3%).

Evaluation Studies as Topic↗

PubMed1995

Problems in interpreting HIV sentinel seroprevalence studies.

Estimating human immunodeficiency virus (HIV) prevalence from sentinel seroprevalence studies is difficult. We characterize these studies and show that most are investigations of incompletely defined (hypothetical) cohorts and are usually based on nonprobability samples. Prevalence in HIV sentinel serosurveys is also time-averaged and vulnerable to several time-dependent sources of bias (e.g., migration, deaths, and changes in incidence). Assumptions must be made that these time-dependent biases did not meaningfully affect the data, and this can be helped by reducing the period of investigation. Furthermore, we show that "reliability" can not be adequately measured by standard error, that "internal validity" is vulnerable to self-selection bias and laboratory problems, and that "generalizability" is limited. We propose that what is needed is a procedure (like formal metaanalysis methods) incorporating information from several separate HIV sentinel seroprevalence studies, in a manner that is reproducible and can take into consideration the differences between studies.

Acquired Immunodeficiency Syndrome↗