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Interpreting the term selection bias in medical research.

The issue of selection bias is often raised in the critical appraisal of medical studies, but it is often poorly defined and misunderstood. This paper, describes three common patterns of use of the term selection bias and their effects on study results. The three ways in which selection bias is used are related to 1) selection of representative subjects, 2) selection of subjects to exposures, and 3) selection of subjects at outcome. Avoidance of bias in the first of these issues, selection of representative subjects, enhances the ability to generalize a study's results. The other two uses of selection bias relate to the internal validity of studies. The selection of subjects to exposures without randomization in observational studies can distort results because of confounding variables. The selection of study subjects at outcome in case-control and cross-sectional studies can distort study findings if selection into the study is distorted according to exposure status. Readers of medical studies should understand the different implications of these uses to improve their critical evaluation of studies. Writers and discussants should be aware of these differences and provide clarifying details when they use the term.

Case-Control Studies↗

[Adaptation and normalization of the Alzheimer's disease Assessment Scale for Spain (NORMACODEM) (II)].

UNLABELLED: This report is part of a project for norming cognitive and functional instruments that assess dementia (NORMACODEM). To adapt and norm the Alzheimer's Disease Assessment Scale (ADAS) for use in Spain. Two hundred fifty-four controls, 86 patients with minor memory/cognitive disorders without dementia (deterioration without dementia, DWD), 111 patients with Alzheimer-type dementia (ATD). Statistical description. Multivariate linear regression. Crossed validation. Internal consistency and test-retest (n = 48). The mean scores (SD) obtained were as follows. CONTROLS: ADAS-Cog = 8.0 (3.4), ADAS-Noncog = 2.9 (2.9), ADAS-Tot = 10.9 (4.6). DWD: ADAS-Cog = 11.37 (5.1), ADAS-Noncog = 4.9 (4.3), ADAS-Tot = 16.2 (7.0). ATD: ADAS-Cog = 31.8 (5.1), ADAS-Noncog = 10.3 (4.3), ADAS-Tot = 42.2 (20.7). Multiple regression analysis revealed that educational level and age were significantly associated with the ADAS-Cog score. The internal consistency of the ADAS-Cog was 0.963. The test-retest procedure yielded linear correlation, coefficients of 0.93 for the ADAS-Cog, 0.86 for the ADAS-Noncog and 0.95 for the ADAS-Tot. Age and educational level/schooling are associated to the earned on the ADAS-Cog instrument. The present Spanish version of the ADAS has high internal consistency and reproducibility. The instruments can be use for assessment in Spanish populations.

Adult↗

[Experience with Health Quality of Life Questionnaire for the epileptic child (CAVE)].

INTRODUCTION: The practical application of a questionnaire designed to evaluate the quality of life of an epileptic child, known as the CAVE test, is described. This is the first scale of its kind. The test consists of 8 parameters: conduct, attendance at school, learning, independence, social relationships, frequency of crises, intensity of crises and parental opinion. Each aspect is given a score, from a minimum of 1 point to a maximum of 5 points. MATERIAL AND METHODS: A total of 203 tests were carried out. 179 of these were considered to be useful. Nine Spanish neuropediatric departments took part in this study. The age limits were from 0 to 14 years old. The best results showed a direct relationship to the children's age, idiopathic etiology and monotherapy as treatment. The quality of life worsened from those with partial simple crises to those with typical absences and generalized tonic-clonic crises. The lowest scores were found in children with infantile spasms and in those with Lennox-Gastaut syndrome. There was a clear statistical relationship between the highest score obtained and the best clinical condition, with regard to the frequency and intensity of crises. Parental opinion was in keeping with the clinical evaluation of the disorder to a certain extent. CONCLUSION: The study is still in progress, so as to interview 1000 children altogether. Then any modifications considered advisable will be made by the multicentre group of the Sociedad Española de Neurología Pediátrica, and may be validated internationally.

Adolescent↗

[Hemorrhagic complications and thrombotic phenomena in oral anticoagulation of elderly patients].

OBJECTIVE: To retrospectively analyze the hemorrhagic complications and thrombotic events associated with aging and the degree of anticoagulation in a series of ambulatory patients treated with acenocumarol and controlled in a specialized anticoagulant therapy unit. PATIENTS AND METHODS: A total of 1,613 ambulatory patients were studied. Patients were divided into two groups (group 1, 645 patients > 65 years old, mean age 71.7 +/- 4.5 years; INR, 2.1-2.8; group 2, 968 patients < or = 65 years, mean age 53.7 +/- 10 years; INR, 2.8-4.2) for a time period of twelve months. The prevalence of hemorrhagic complications and severity according to a validated international index (Bleeding Severity Index), as well as the thrombotic events occurred despite anticoagulation therapy. RESULTS: Fifty-two hemorrhagic events (8/100 patients-year) were recorded in the older group (group 1). Twenty-six cases were considered banal episodes, 24 minor hemorrhages and two major hemorrhages. Ten patients (1.5/100 patients-year) had thrombotic complications. In the younger group (group 2) 150 bleeding episodes were recorded (15 patients-year), of which 11 were banal, 39 minor hemorrhages and no major hemorrhages. Only eight patients 0.8/100 patients-year) had thrombosis. The presence of local factors predisposing to bleeding was more common in group 1 (p < 0.001). Older patients had in general more complications than younger patients (p < 0.001), but no significant differences were observed between the occurrence of hemorrhages or thrombosis independently analyzed between both groups. The rate in the therapeutic range was greater among the youngest individuals (p < 0.05). CONCLUSIONS: Our results support the idea that patients with advanced age can benefit from a less aggressive anticoagulation. A statistical trend was observed, although not significant, towards the presence of major hemorrhages and thrombosis in this group of patients. The presence of local or predisposing factors to hemorrhage (underlying disease and NSAIDs use) is more relevant in patients with advanced age.

Acenocoumarol↗

[Room air contamination with halothane during pediatric bronchoscopy].

Halothane anesthesia is frequently used for pediatric bronchoscopy. A disadvantage of the equipment used, a rigid bronchoscope together with inhalation anesthesia is the contamination of the working environment. The aim of this study was to determine the exposure of anesthetist and endoscopist during pediatric bronchoscopy under halothane anesthesia in a worst-case working environment and to compare these measurements with the currently valid international threshold values. Ten children (ASA I-III) scheduled for diagnostic bronchoscopy were included in the study. After induction with thiopentone and relaxation with atracurium all children were intubated with a rigid bronchoscope and manually ventilated through a bypass of the bronchoscope. Anesthesia was maintained by means halothane (0.5-2.0 vol%) in 100% oxygen with a flow of 10 l/min. The investigation was done in an operating room without air conditioning and scavenging system. Trace concentrations were measured every 2 minutes in the breathing zones of the anesthetist and the endoscopist by means of a highly sensitive direct reading instrument. Lower detection limit was 0.02 ppm. The mean age (+/- SD) of the children was 29.9 +/- 15.9 months (range: 4 weeks-48 months). Ventilation and oxygenation were stable throughout the bronchoscopic procedure. Mean exposure (+/- SEM) to halothane was 57.7 +/- 18.9 ppm for the anesthetist and 96.3 +/- 22.9 ppm for the endoscopist. The difference was statistically significant (ANOVA, P < 0.05). All international threshold values (2-50 ppm) were exceeded by far. Peak concentrations higher than 200 ppm halothane could be detected several times. The main result of the present study is that under the given situation in the operating room with insufficient room ventilation and no scavenging system halothane anesthesia for rigid bronchoscopy in children results in an occupational exposure that is higher than all known health regulation guidelines. Therefore, in case of insufficient working conditions total intravenous anesthesia might be a better alternative also in very small infants.

Air Pollutants, Occupational↗

[Exposure of the pediatric surgeon to inhalation-anesthetic during pediatric bronchoscopy procedures].

BACKGROUND: General anaesthetic agents are frequently used for paediatric bronchoscopy. A disadvantage of this open system anaesthesia seems to be the contamination of the working environment. The aim of this study was to determine the exposure of the endoscopist during paediatric bronchoscopy under general anaesthesia in different working environments and to compare these measurements with the currently valid international threshold limit values. MATERIAL AND METHODS: 25 children (ASA I-III) scheduled for diagnostic bronchoscopy were included in the study. After inhalational induction all children were intubated with a nonflexible bronchoscope and manually ventilated through a side arm of the bronchoscope. Maintenance of anaesthesia was achieved with sevoflurane (2-3 vol%) in 80% oxygen. Trace concentrations were measured every 90 seconds in the breathing zones of the paediatrician by means of a highly sensitive direct-reading instrument (Brüel & Kjaer 1302). The lower detection limit was 0.02 ppm. The investigation was done in an OT with and without air conditioning and scavening system. RESULTS: The mean age of the children was 50.3 months (range: 3-109 months). Ventilation and oxygenation were stable throughout the bronchoscopic procedure. Mean exposure of the paediatrician without air-conditioning and scavening system to sevoflurane was over 50 ppm for the endoscopist. All international threshold limit values were exceeded. Peak concentrations higher than 100 ppm sevoflurane were detected repeatedly in 40% of anaesthesias. During bronchoscopy in the operating room equipped with laminar air flow (20.2 air exchanges per hour) and narcotic gas evacuation (30 l/min) the mean exposure of the paediatrician was 26.4 ppm sevoflurane. CONCLUSIONS: The main finding of the present study is that under inhalation anaesthesia with sevoflurane for paediatric bronchoscopy occupation exposure is higher than the limits stated in all known health regulation guidelines. Therefore, in case of such working conditions, the use of total intravenous anaesthesia is advocated also in very small infants.

Adult↗

Population pharmacokinetics of ciprofloxacin in patients with liver impairments analyzed by NPEM2 algorithm--a retrospective study.

In order to develop a population pharmacokinetic model for ciprofloxacin after single oral dosing in patients with liver impairments, a retrospective population analysis of already published data was undertaken. The purpose of the study was to compare the population model parameter estimates for ciprofloxacin obtained with the non-parametric expectation maximization (NPEM2) algorithm based on a full data set (NPEM2-FULL) with those based on a set of 3 randomly chosen time/concentrations data (NPEM2-3RPs). Parameter values generated by the standard two-stage (STS) approach using traditional data-rich situation were used as a "gold standard" for comparative purposes. There was no significant difference between parameter means at p < 0.05 for Gauss-Newton and maximum a posteriori Bayesian (MAPB) estimators. The values of k(s) (min/ml/h) as estimated by STS and NPEM2-FULL models, on the one hand, and by STS and NPEM2-3RPs population models on the other hand (0.001, 0.00095, and 0.001, respectively), were not significantly different (p = 0.1457, respectively p = 0.6276). The population models values of k(s) suggest that good approximation between ciprofloxacin renal clearance and creatinine clearance could be expected for most of the patients and support previous observations that creatinine clearance is a meaningful predictor for ciprofloxacin elimination from the body. The 3 population models estimated Vs/F (l/kg) without significant difference. The predictive performance of these population models was subsequently assessed using internal validation approach. The 3 population models demonstrated comparable accuracy and precision in Bayesian forecasting of drug plasma levels of validation group patients based on 1 random and 2 suboptimal prior drug concentrations. There was, however, a one-order of magnitude decrease in population models bias when 2 suboptimal data points were used as Bayesian priors.

Administration, Oral↗

A descriptive study of verocytotoxigenic Escherichia coli (VTEC) cases reported in Ontario, 1990-1994.

Characteristics of VTEC cases identified through routine surveillance in Ontario between 1990 and 1994 are described. Information was extracted from the Reportable Disease Information System (RDIS) of Ontario and was evaluated for its completeness and internal validity. A total of 2,441 VTEC cases were identified for the five-year study period corresponding to an average annual rate of 4.8 cases per 100,000. Sixteen deaths were recorded. Bloody diarrhea was reported for 546 patients (40%) and was the most frequently reported symptom. For most cases, the home was recorded as the likely risk setting (36%). Food was incriminated as the source of infection for more than 36% of cases. Nine (69%) of the thirteen data fields compulsory for transmission to the Ontario Ministry of Health had less than 10% of combined missing and unspecified values. Fields describing risk factors had greater than 56% of entries missing or unspecified.

Adolescent↗

Clinical outcome research in complementary and alternative medicine: an overview of experimental design and analysis.

This article serves as a primer for those beginning clinical research in complementary and alternative medicine. The authors provide a basic overview of important experimental design and statistical issues, of which clinical researchers in the area of complementary and alternative medicine must be aware when attempting to demonstrate the effectiveness of particular treatment modalities. As the article suggests, science is an inferential process, and experimental investigations can vary greatly in methodological integrity. Key concepts in clinical outcome research such as internal validity, statistical conclusion validity, and the appropriate measurement and operational definitions of outcomes are discussed. New scientific approaches that are evolving because of paradigm shifts in science (e.g., chaos theory) are also reviewed. Suggestions are provided to further develop an understanding of clinical outcome research methodology.

Complementary Therapies↗

[Is homeopathy more than a placebo?].

Homeopathy can be characterized by three axioms "treating like with like" (law of similars), "increasing effects with increasing potency" (potentization) and "effects on the basis of ultra-high dilutions" (beyond-molecular effects), where it is unlikely that the dilutions contain a single molecule of the original substance. On the basis of these tenets and the clinical evidence further research priorities are developed. Current reviews indicate small homeopathic verum effects, even after adjustment for internal validity and publication-bias. However, the results remain disputable, because reproducibility isn't assured by independent examiners. For further validation, independent replication of studies with high quality, including specially treatment with high-potencies according to law of similars, seem to be important. The prerequisites for a homeopathy-specific study methodology (inclusion of populations according to their homeopathic diagnosis) still are not fulfilled today. There is neither convincing evidence for specific drug pictures by placebo-controlled drug provings, nor is the reliability of homeopathic diagnosis proven. By reason of extensive, individual interviews, preceeding every classical homeopathic remedy finding, placebo-effects could play an important therapeutical role. The relevance of homeopathic placebo-effects should be explored against other sham treatments and an untreated group.

Clinical Trials as Topic↗

Patient-based assessment of the outcomes of implant therapy: a review of the literature.

PURPOSE: This paper reviews the literature on patient-based assessments of implant therapy. MATERIALS AND METHODS: A search of the literature produced 22 papers describing 19 studies. RESULTS: Only 3 of the 19 studies were randomized controlled trials. Consequently, most have design flaws that threaten their internal validity. In addition, the measurement of patient-based outcomes was generally poor, further weakening the evidence provided by the research conducted to date. The randomized trials indicate that implants improve chewing ability and satisfaction with dentures but have not demonstrated effects with respect to the quality of life. CONCLUSION: Further research is needed using randomized controlled trial designs. Outcome measures need to be more carefully selected so as to reflect patients' concerns.

Dental Implantation, Endosseous↗

[Validation of the "International Consultation on Incontinence Questionnaire -- Short Form" (ICIQ-SF) for Portuguese].

OBJECTIVE: To translate into and validate for Portuguese the "International Consultation on Incontinence Questionnaire -- Short Form" (ICIQ-SF), a condition-specific quality-of-life questionnaire for patients with urinary incontinence. METHODS: Two Brazilians independently translated the original ICIQ-SF into Portuguese. These two translations were harmonized, and then checked by independent back-translation by two native English speakers. The harmonized translation was pre-tested in a pilot study on 20 patients. The final version of the ICIQ-SF in Portuguese was applied to 123 consecutive patients aged 16 or over (29 males and 94 females) with a complaint of urinary incontinence, who had sought the Department of Urogynecology and Uroneurology of the School of Medical Sciences of Unicamp. The Portuguese version of the King's Health Questionnaire (KHQ) was also applied to the same group. The psychometric properties of the questionnaire, such as reliability and construct validity were assessed. RESULTS: The median age was 53 years (range: 16 to 86). The mean retest interval for the ICIQ-SF was 14.37 days (range: 6 to 41). No changes from the original format of the ICIQ-SF were observed at the end of the process of translation and cultural adaptation. The internal consistency was high (0.88), as measured by the Cronbach alpha coefficient. The test-retest value was considered moderate to strong, as measured by the weighted Kappa index (range: 0.72 to 0.75) and Pearson correlation coefficient (0.89). The correlation between the ICIQ-SF and KHQ was considered to be moderate to good for most items (range: 0.44 to 0.77). The evaluation of the construct and concurrent validity was also satisfactory and statistically significant. CONCLUSIONS: The "International Consultation on Incontinence Questionnaire" (ICIQ-SF) was successfully translated into Portuguese and validated for application to Brazilian female and male patients complaining of urinary incontinence, with satisfactory reliability and construct validity.

Adolescent↗

Reliability, internal consistency, and validity of data obtained with the functional gait assessment.

BACKGROUND AND PURPOSE: The Functional Gait Assessment (FGA) is a 10-item gait assessment based on the Dynamic Gait Index. The purpose of this study was to evaluate the reliability, internal consistency, and validity of data obtained with the FGA when used with people with vestibular disorders. SUBJECTS: Seven physical therapists from various practice settings, 3 physical therapist students, and 6 patients with vestibular disorders volunteered to participate. METHODS: All raters were given 10 minutes to review the instructions, the test items, and the grading criteria for the FGA. The 10 raters concurrently rated the performance of the 6 patients on the FGA. Patients completed the FGA twice, with an hour's rest between sessions. Reliability of total FGA scores was assessed using intraclass correlation coefficients (2,1). Internal consistency of the FGA was assessed using the Cronbach alpha and confirmatory factor analysis. Concurrent validity was assessed using the correlation of the FGA scores with balance and gait measurements. RESULTS: Intraclass correlation coefficients of.86 and.74 were found for interrater and intrarater reliability of the total FGA scores. Internal consistency of the FGA scores was.79. Spearman rank order correlation coefficients of the FGA scores with balance measurements ranged from.11 to.67. DISCUSSION AND CONCLUSION: The FGA demonstrates what we believe is acceptable reliability, internal consistency, and concurrent validity with other balance measures used for patients with vestibular disorders.

Adult↗

Measuring health status in psychiatric community surveys: internal and external validity of the Spanish version of the SF-36.

The aims of the present study were to determine the acceptability of the Spanish version of the Short Form (SF-36) health survey questionnaire for its use in mental health research on the general population, and to evaluate its internal and external validity, using data obtained from a representative community sample of 1250 adults of working age. The internal consistency of the different dimensions of the questionnaire was high. Concurrent validity was tested by examining its correlation with the 12-item General Health Questionnaire (GHQ-12). Construct validity was determined by studying the extent to which scores on different variables reflected the expected distribution of health status for and between certain groups. Our findings provide strong evidence for the acceptability and validity of the SF-36 when used as part of a community mental health survey.

Adolescent↗

[Failure effects and gender differences in perfectionism].

Perfectionism is a dimension which has been studied very little as a separate entity. It is not even considered as a nosological factor. No classification of the medical sciences underlines its importance other than to speak of a personality trait, of an aspect, or of a parameter. Nevertheless, perfectionism is related to multiple disorders such as depression (18, 20, 36), suicide (8, 16, 55), nutritional problems (11, 28), anxiety (3), obsessive-compulsive personality disorder (53), social phobia (2), as well as insomnia (46). Certain authors stress the possible role of perfectionism in the development or the persistence of a substantial number of these disorders (7, 22, 38). Given these facts, it is all the easier to understand the interest shown by clinicians and researchers in the subject. Better detection and evaluation of its impact on behaviour is important in putting therapies in place (6, 53). Relationships between perfectionism and fear of failure have been approached (21, 51, 54). Correlations between perfectionism and high levels of state and trait anxiety have been demonstrated (23). The evaluation of perfectionism has been dealt with very little. Some questionnaires devote a sub-category to it, such as the Eating Disorder Inventory and the Irrational Beliefs Test. However, recently, it has been recognized that perfectionism is a multidimensional construct. Two Multidimensional Perfectionism Scales have been developed and investigated in relative isolation. Frost, Marten, Lahart and Rosenblate defined perfectionism as the setting of excessively high standards for performance associated with critical self-evaluation. Six dimensions are described: concern over making mistakes, high personal standards, parental expectations, parental criticism, doubt about quality of performance and organization. Internal consistency and validity have been established (25, 26). Hewitt and Flett (30, 31, 33, 35) have developed another approach where three dimensions of perfectionism are described: SOP (Self Oriented Perfectionism) related to high standards and self criticism, SPP (Socially Prescribed Perfectionism) related to the need of approval from others and fear of negative evaluation, OOP (Other-Oriented Perfectionism) reflecting a tendency to set high expectations for others and to evaluate them in a demanding way; this component is related, especially for males, to self-esteem, hostility and authoritarianism. Validity and internal consistency have been established too (30, 31, 35). The Frost and al's Multidimensional Perfectionism Scale and the Hewitt and Flett's scales are closely associated, except concerning the OOP. Because this component could provide new information, we have chosen the second scale, referring to the French translation and validation of Labrecque (45). EMP is the French name of MPS; it is a self-report questionnaire of 45 questions, in fact three subscales of 15 items rated on a 7-point Likert-type scale. MPS was administered to 617 first year students at the university of Liège (table II). Differences are considered according to gender and experience of failure i.e. the fact of repeating an academic year. We realized a component analysis with promax rotation. Among the different possibilities offered by the scree-test the choice of a 4 factor solution stresses the original structure: SOP (14 items), SPP (12 items), OOP (9 items) and anti OOP (10 items); the last one is additional but allows for respecting semantics and saturation of the items. The first aim of confirming validity and internal consistency is satisfactory. In other respects the multidimensional structure of the concept leads to consideration of a positive, adaptive perfectionism and a more negative perfectionism, facilitating psychopathology (59, 60, 61). So it seems interesting to compare the different components of MPS in order to find an eventual sex-failure effect. The evaluation of perfectionism is obvious, considering it as a personality trait, but it can be used also in taking into account stress and its impact, for instance that of academic performance (29, 37, 39, 58). Conferring on MPS more pertinence in gender differentiation and failure evaluation is an other goal of this research. Through the particular choice of statistical results, sex and sex-failure effects can be demonstrated: a MANOVA underlines sex effect (lambda de Wilks = 0.96, p = 0.001) and sex-failure effect (lambda de Wilks = 0.98, p = 0.05). Structure of MPS is different in four groups (FE: women with failure, FnE: women without failure, ME: men with failure, MnE: men without failure). ANOVA show differences of MPS3, MPS1 and MPS2. Far more promising is the use of LISREL method allowing for the construction of a coherent model of relationships between some dimensions of MPS and Test-Anxiety, approached here with THEE (test d'habileté aux études et à leur évaluation) French abbreviated version (49) of TASTE (Test for Ability to Study and Evaluation). In fact according to the literature of fear of failure, girls score higher on anxiety and procrastination but less on self-confidence. The structural model shows different pathways, more especially between SPP (socially prescribed perfectionism), T2 (sense of incompetence) and T1 (anxiety). SOP (self oriented perfectionism) and SPP (socially prescribed perfectionism) by girls are very much correlated; it seems that they are more subjected to society and its exigencies of studying but consequently they are more at risk of anxiety and a sense of incompetence. SOP (self oriented perfectionism) by boys functions more indiscriminately of SPP (socially prescribed perfectionism) and is negatively correlated with self-incompetence; boys are more self-confident but they usually procrastinate more probably because failure expectancies would be particularly harmful for their self-esteem; consequently, failure should be related to something else than their own capacity; this may be an explanation of the high rate of male dropouts and failure in the first year at the university of Liège; also a factor explaining the female domination at the university. In the same way the first choice of studies is moving towards shorter and less difficult orientation (46). In case of failure the model is very similar according to gender: SOP (self oriented perfectionism) and T1 (anxiety) are directly connected; SOP and SPP are in this case better correlated by boys but the path between SPP, sense of incompetence and anxiety is less significant than in girls. In conclusion, providing some modifications according to semantics, the choice of a four factor solution allows for confirmation of the original structure of MPS and for internal consistency. The different components of MPS vary according to gender: SOP and more OOP discriminate men and women; SPP allows for differentiating women with failure. A structural model enhances the role of perfectionism in the cognitive and behavioural contexts; for instance it clarifies its action on fear of failure and success rates according to gender.

Adult↗

[Internal consistency, factorial validity and discriminant validity of the French version of the psychological demands and decision latitude scales of the Karasek "Job Content Questionnaire"].

BACKGROUND: The job demands-control model developed by Karasek has greatly influenced research on psychosocial factors at work and health. Validity of the English version of the psychological demands and decision latitude scales is documented. Psychometric qualities of the French version are investigated here in a representative sample of the general population, including blue-collars and white-collars. METHODS: The French translation of the psychological demand and decision latitude scales was administered by interview in a representative sample of the Quebec working population (N = 1,110). Internal consistency and factorial validity of the instrument were studied among white-collars and blue-collars separately. Discriminant validity was assessed for the whole population. RESULTS: Cronbach alpha coefficients, varying between 0.68 and 0.85, support the internal consistency of the scales. Demographic distribution of the scales and intercorrelations were consistent with the English version. Results of the factor analysis were consistent with the two dimensions expected from the theory. Mean scale scores and variations in the prevalence of high psychological demands combined with low decision latitude by age, sex, education, and job category support the discriminant validity of the instrument. CONCLUSIONS: Results support internal consistency, factorial validity, and discriminant validity of the French version of the psychological demands and decision latitude scales of the Karasek "Job Content Questionnaire" for white-collars and for blue-collars of the general population.

Adolescent↗

A short questionnaire (IRQ) to assess injecting risk behaviour.

AIM: To develop a short injecting risk questionnaire (IRQ) to measure sharing of injecting equipment. DESIGN: Matrix design with quota assignment, designed to compare the questionnaire when used by interview and self-completion, in agency and community settings, by agency staff and fieldworkers, with different injectors (age < 26 vs. 26+; male vs. female, opiate vs stimulant injectors), and in different geographical areas. SETTINGS: Drug treatment and helping agencies, and community settings, in England. PARTICIPANTS: Drug users who had injected in the last 4 weeks. MEASUREMENTS: Questions measured different aspects of equipment sharing. Questionnaire performance assessed by question acceptability, test-retest (parallel forms) reliability, inter-rater reliability, inter-instrument reliability, internal reliability, construct validity and internal collateral validity. Statistical tests included product moment correlation, principal components analysis, and Cronbach's alpha. FINDINGS: The questionnaire was highly acceptable. Test-retest correlations were all high and significant, questions performed well in all conditions, with no differences by site (agency vs. out-of-contact), order (interview or self-completion first), administration (staff vs. fieldworker), elapsed time or subject characteristics. The questionnaire had high internal reliability (Cronbach's alpha > +0.86), and items measured a similar domain with all questions loading highly (> 0.32) on a single factor which accounted for > 42% of the variance. The complete IRQ elicited higher reports of equipment sharing (77%) than a single question (56%). CONCLUSIONS: IRQ performs well in a variety of settings, when administered in different ways to different kinds of IDUs. A single question on 'sharing' elicits fewer positive responses than the use of multiple questions about different sharing practices.

Adult↗

Development and validation of the international knee documentation committee subjective knee form.

A committee of international knee experts created the International Knee Documentation Committee Subjective Knee Form, which is a knee-specific, rather than a disease-specific, measure of symptoms, function, and sports activity. The purpose of this study was to evaluate the reliability and validity of the new International Knee Documentation Committee Subjective Knee Form. To provide evidence for reliability and validity, we administered the final version of the form, along with the Short Form-36, to 533 patients with a variety of knee problems. Analyses were performed to determine reliability, validity, and differential item function related to age, sex, and diagnosis. Factor analysis revealed a single dominant component, making it reasonable to combine all questions into a single score. Internal consistency and test-retest reliability were 0.92 and 0.95, respectively. Based on test-retest reliability, the value for a true change in the score was 9.0 points. The International Knee Documentation Committee Subjective Knee Form score was related to concurrent measures of physical function (r = 0.47 to 0.66) but not to emotional function (r = 0.16 to 0.26). Analysis of differential item function indicated that the questions functioned similarly for men versus women, young versus old, and for those with different diagnoses. In conclusion, the International Knee Documentation Committee Subjective Knee Form is a reliable and valid knee-specific measure of symptoms, function, and sports activity that is appropriate for patients with a wide variety of knee problems. Use of this instrument will permit comparisons of outcome across groups with different knee problems.

Factor Analysis, Statistical↗