An inter- and intra-laboratory comparison of breath ¹³CO2analysis.

BACKGROUND: ¹³C breath test analysis requires accurate ¹³CO2measurements. AIM: To perform a multicentre study to evaluate the repeatability and reproducibility of breath ¹³CO2analysis. METHODS: Two series of 25 paired randomly coded tubes (each consisting of 23 ¹³CO2-enriched breath samples and two samples of standard reference pure CO2with certified δ ¹³C(PDB)) were sent to participating centres for ¹³CO2measurement. Each series of tubes was analysed 10 days apart. The repeatability and reproducibility of ¹³C measurements was assessed by Mandel's k and h statistics. RESULTS: Twenty-two centres participated in the study: 18 showed good inter- and intra-laboratory variability, whilst four showed abnormally high inter- or intra-laboratory variability. Breath test results were also significantly affected by the accuracy of the ¹³C analytical procedures. CONCLUSIONS: A low accuracy of ¹³C measurements may significantly affect the results of breath tests, leading to inappropriate clinical decisions. Standardization of ¹³C analysis is required to guarantee optimal ¹³C measurements and accurate ¹³C breath test results.

Quality of life following bladder training in older women with urinary incontinence.

This study investigated the changes in quality of life following a randomized controlled 6-week trial of bladder training in 123 older women with urinary incontinence. Both clinical (diary, pad test) and quality of life measures (Incontinence Impact Questionnaire (IIQ), Center for Epidemiological Studies-Depression Scale (CES-D)) and visual analog scales on symptom burden were obtained at baseline, 6 weeks and 6 months following treatment. All subscales and the composite scale of the IIQ and the visual analog scales were significantly improved following bladder training, with effects maintained 6 months later. No changes were observed in CES-D scores. Women with genuine stress incontinence and those with detrusor instability with or without concomitant stress incontinence had similar improvements. We conclude that bladder training is effective in improving the quality of life of incontinent women regardless of urodynamic diagnosis.

Short forms to assess life quality and symptom distress for urinary incontinence in women: the Incontinence Impact Questionnaire and the Urogenital Distress Inventory. Continence Program for Women Research Group.

This article describes short form versions of the Incontinence Impact Questionnaire (IIQ) and the Urogenital Distress Inventory (UDI). These instruments assess life impact and symptom distress, respectively, of urinary incontinence and related conditions for women. All subsets regression analysis was used to find item subsets that best approximated scores of the long form versions. The approach succeeded in reducing the 30-item IIQ and the 19-item UDI to 7- and 6-item short forms, respectively. The short form versions may be more useful than the long form versions in many clinical and research applications.

Health-related quality of life measures for women with urinary incontinence: the Incontinence Impact Questionnaire and the Urogenital Distress Inventory. Continence Program in Women (CPW) Research Group.

Urinary incontinence (UI) is a relatively common condition in middle-aged and older women. Traditional measures of symptoms do not adequately capture the impact that UI has on individuals' lives. Further, severe morbidity and mortality are not associated with this condition. Rather, UI's impact is primarily on the health status and health-related quality of life (HRQOL) of women. Generic measures of HRQOL inadequately address the impact of the condition on the day-to-day lives of women with UI. The current paper presents data on two new condition-specific instruments designed to assess the HRQOL of UI in women: the Urogenital Distress Inventory (UDI) and the Incontinence Impact Questionnaire (IIQ). Used in conjunction with one another, these two measures provide detailed information on how UI affects the lives of women. The measures provide data on the more traditional view of HRQOL by assessing the impact of UI on various activities, roles and emotional states (IIQ), as well as data on the less traditional but critical issue of the degree to which symptoms associated with UI are troubling to women (UDI). Data on the reliability, validity and sensitivity to change of these measures demonstrate that they are psychometrically strong. Further, they have been developed for simple, self-administration.

Latent class analysis of substance abuse patterns.

This chapter discusses use of latent class analysis (LCA) as a tool for identifying substance use patterns in cross-sectional data. LCA serves as an exploratory and data reduction tool that helps clarify the nature of substance use and may provide insight concerning effective prevention strategies. LCA is well suited to categorical data such as typically are collected in substance use research. Use of LCA can be divided into three steps: (1) model comparison and selection, (2) assignment of cases to latent classes, and (3) interpretation of the latent classes. Quantitative indices of model fit may assist model comparison and selection. Latent classes can be interpreted by examining probabilities of substance use in each latent class and by examining differences on exogenous variables. Limitations, extensions, and software for LCA are discussed. An example illustrates use of LCA with actual data collected from a current substance abuse prevention study.

A latent trait finite mixture model for the analysis of rating agreement.

This article presents a latent distribution model for the analysis of agreement on dichotomous or ordered category ratings. The model includes parameters that characterize bias, category definitions, and measurement error for each rater or test. Parameter estimates can be used to evaluate rater performance and to improve classification or measurement with use of multiple ratings. A simple maximum likelihood estimation procedure is described. Two examples illustrate the approach. Although considered in the context of analyzing rater agreement, the model provides a general approach for mixture analysis using two or more ordered-caregory measures.

Improving task comprehension in the measurement of health state preferences. A trial of informational cartoon figures and a paired-comparison task.

Information concerning people's relative preferences for health care outcomes is usually obtained using questionnaires which ask subjects to imagine health states of various kinds. When using illness- or treatment-specific states, elaborate descriptions of patients' quality of life may adequately convey to the rater a sense of the real situation. Such descriptions are not possible with generic questionnaires, which frame outcomes in general terms, such as pain, limits on activities, etc. This study evaluated two methods for facilitating task comprehension with generic preference-assessment instruments: (1) use of informational figures that provide visual representations of the described health state, and (2) measurement of preferences by means of a paired-comparison task. The use of figures did not change rating variance or the number of counter-intuitive ratings, but did improve one-week test-retest reliability. Paired comparisons had reliability comparable to the direct rating tasks and reduced the number of counter-intuitive ratings, although not to a statistically significantly extent.

Latent class analysis of diagnostic agreement.

We describe methods based on latent class analysis for analysis and interpretation of agreement on dichotomous diagnostic ratings. This approach formulates agreement in terms of parameters directly related to diagnostic accuracy and leads to many practical applications, such as estimation of the accuracy of individual ratings and the extent to which accuracy may improve with multiple opinions. We describe refinements in the estimation of parameters for varying panel designs, and apply latent class methods successfully to examples of medical agreement data that include data previously found to be poorly fitted by two-class models. Latent class techniques provide a powerful and flexible set of tools to analyse diagnostic agreement and one should consider them routinely in the analysis of such data.

Structural analysis of diagnostic disagreements.

When different psychiatrists examine a patient, disagreements often occur. Data that can be used to clarify the factors responsible for disagreements are collected routinely but not systematically analyzed. This paper discusses two quantitative methods, cluster analysis and multidimensional scaling, for describing structural properties of disagreement data and for determining from them steps that can be taken to upgrade inter-rater reliability.

A design-independent method for measuring the reliability of psychiatric diagnosis.

The several different versions of the kappa coefficient currently in use can be seen as variants of a single basic computational method. This paper present general formulas for calculating kappa, both to measure the overall reliability of a set of diagnostic categories and to measure the specific reliability of individual categories. The formulas extend the range of situations in which kappa can be calculated to include multiple-rater, partially crossed designs of the sort that researchers frequently encounter.

Client correlates of community informant adjustment ratings.

Explored similarities and differences among home and community adjustment ratings by clients, community informants, and psychiatrists. Minnesota Multiphasic Personality Inventories, and Personality Adjustment and Role Skills (PARS) scales (Ellsworth, 1975) were administered to 169 consecutively-admitted psychiatric patients. Psychiatrists rated each client on the Brief Psychiatric Rating Scales and 141 community informants rated client's home and community adjustment on the PARS. Simple, multiple, and canonical correlational analyses were performed with scores from these tests. Although clients, community informants, and psychiatrists agree when rating clients' symptomatology, nevertheless each person highlighted different aspects of adjustment. Moreover, "impression management" (as measured by subtle-obvious MMPI scales) emerged as influential. These two findings suggest that outcome assessment must be based not only on ratings from multiple perspectives but also outcome assessment must entertain possible biases among raters. Supplementary analyses indicated that outcome assessment for psychiatric clients can be improved by adding response style scales which evaluate dimensions of "sick" and "healthy" symptom presentation and by identifying interaction of diagnosis with ratings of home and community and adjustment.