Karen H. Sousa

Teacher's Corner: Testing Measurement Invariance of Second-Order Factor Models.

We illustrate testing measurement invariance in a second-order factor model using a quality of life dataset (n = 924). Measurement invariance was tested across 2 groups at a set of hierarchically structured levels: (a) configural invariance, (b) first-order factor loadings, (c) second-order factor loadings, (d) intercepts of measured variables, (e) intercepts of first-order factors, (f) disturbances of first-order factors, and (g) residual variances of observed variables. Given that measurement invariance at the factor loading and intercept levels was achieved, the latent factor mean difference on the higher order factor between the groups was also estimated. The analyses were performed on the mean and covariance structures within the framework of the confirmatory factor analysis using the LISREL 8.51 program. Implications of second-order factor models and measurement invariance in psychological research were discussed.

A Comparison of Bifactor and Second-Order Models of Quality of Life.

Bifactor and second-order factor models are two alternative approaches for representing general constructs comprised of several highly related domains. Bifactor and second-order models were compared using a quality of life data set (N = 403). The bifactor model identified three, rather than the hypothesized four, domain specific factors beyond the general factor. The bifactor model fit the data significantly better than the second-order model. The bifactor model allowed for easier interpretation of the relationship between the domain specific factors and external variables, over and above the general factor. Contrary to the literature, sufficient power existed to distinguish between bifactor and corresponding second-order models in one actual and one simulated example, given reasonable sample sizes. Advantages of bifactor models over second-order models are discussed.

Putting Wilson and Cleary to the test: analysis of a HRQOL conceptual model using structural equation modeling

Wilson and Cleary (1995) proposed a conceptual model of health-related quality of life (HRQOL) that integrates both biological and psychological aspects of health outcomes. There are five different levels in their model, namely, physiological factors, symptom status, functional health, general health perceptions, and overall quality of life. Their model has been widely applied to different populations, including patients living with cancer, Parkinson’s disease, arthritis, and HIV+/AIDS. However, their conceptual model has only been partially examined. That is, the five major concepts have not been examined simultaneously. Using structural equation modeling (SEM), the Wilson and Cleary HRQOL model was validated in patients living with HIV from the AIDS Time-Oriented Health Outcomes Study. The results showed that the HRQOL model fit the data adequately, and the relationships between the constructs were all significant (at p<0.05 level). Based on the modification indexes, an alternative model linking symptom status directly with general health perceptions and overall quality of life was specified. Implication and limitation of the findings are discussed.

Early predictors of severe lower gastrointestinal bleeding and adverse outcomes: a prospective study.

BACKGROUND & AIMSnUnlike in upper tract bleeding, prognostic factors for ongoing or recurrent bleeding from the lower gastrointestinal tract have not been well-defined. The aim of this study was to identify risk factors for severe lower gastrointestinal bleeding and for significant adverse outcomes.nnnMETHODSnAll patients seeking attention at a university emergency department for gastrointestinal bleeding were prospectively identified during a 3-year period. Ninety-four of 448 (21%) admitted patients had lower gastrointestinal bleeding. Clinical predictors available in the first hour of evaluation were recorded. The primary outcome, severe lower gastrointestinal bleeding, was defined as gross blood per rectum after leaving the emergency department associated with either abnormal vital signs (systolic blood pressure < 100 mm Hg or heart rate > 100/min) or more than a 2-unit blood transfusion during the hospitalization. Significant adverse outcomes, including death, were tabulated.nnnRESULTSnThirty-seven patients (39%) had severe lower gastrointestinal bleeding. Independent risk factors for severe lower gastrointestinal bleeding were initial hematocrit </=35% (odds ratio [OR], 6.3; 95% confidence interval [CI], 2.2-16.7); presence of abnormal vital signs (systolic blood pressure < 100 mm Hg or heart rate > 100/min) 1 hour after initial medical evaluation (OR, 4.3; 95% CI, 1.4-12.5); and gross blood on initial rectal examination (OR, 3.9; 95% CI, 1.2-13.2). Nineteen patients (20%) experienced a significant adverse outcome, including 3 deaths. The main independent predictor of adverse outcomes was severe lower gastrointestinal bleeding (OR, 5.3; 95% CI, 1.7-16.5).nnnCONCLUSIONSnRisk factors are available in the first hour of evaluation in the emergency department to identify patients at risk for severe lower gastrointestinal bleeding. Severe lower gastrointestinal bleeding is a significant risk factor for global adverse outcomes.

Establishing measurement invariance: English and Spanish Paediatric Asthma Quality of Life Questionnaire.

Background:Registered nurses and nurse researchers often use questionnaires to measure patient outcomes. When questionnaires or other multiple-item instruments have been developed using a relatively homogeneous sample, the suitability of even a psychometrically well-developed instrument for the new population comes into question. Bias or lack of equivalence can be introduced into instruments through differences in perceptions of the meaning of the measured items, constructs, or both in the two groups. Objective:To explain measurement invariance and illustrate how it can be tested using the English and Spanish versions of the Paediatric Asthma Quality of Life Questionnaire (PAQLQ). Methods:A sample of 607 children from the Phoenix Children’s Hospital Breathmobile was selected for this analysis. The children were of ages 6–18 years; 61.2% completed the PAQLQ in Spanish. Testing measurement invariance using multiple-group confirmatory factor analysis, a series of hierarchical nested models, is demonstrated. In assessing the adequacy of the fit of each model at each stage, both &khgr;2 tests and goodness-of-fit indexes were used. Results:The test of measurement invariance for the one-factor model showed that the English and Spanish versions of the scale met the criteria for measurement invariance. The level of strict invariance (equal factor loadings, intercepts, and residual variances between groups) was achieved. Discussion:Confirmatory factor analysis is used to evaluate the structural integrity of a measurement instrument; multiple confirmatory factor analyses are used to assess measurement invariance across different groups and to stamp the data as valid or invalid. The PAQLQ, a widely used instrument having evidence to support reliability and validity was used separately in English- and Spanish-speaking groups. Traditional methods for evaluating measurement instruments have been less than thorough, and this article demonstrates a well-developed approach, allowing for confident comparisons between populations.

Breast cancer and symptom clusters during radiotherapy.

Background: Symptom clusters assessment shifts the clinical focus from a specific symptom to the patient’s experience as a whole. Few studies have examined breast cancer symptom clusters during treatment, and fewer studies have addressed symptom clusters during radiation therapy (RT). The theoretical underpinning of this study is the Symptoms Experience Model. Research is needed to identify antecedents and consequences of cancer-related symptom clusters. Objective: The present study was intended to determine the clustering of symptoms during RT in women with breast cancer and significant correlations among the symptoms, individual characteristics, and mood. Methods: A secondary data analysis from a descriptive correlational study of 93 women at weeks 3 to 7 of RT from centers in the mid-Atlantic region of the United States, Symptom Distress Scale, the subscales of the Positive and Negative Affect Scale, Life Orientation Test, and Self-transcendence Scale were completed. Results: Confirmatory factor analysis revealed symptoms grouped into 3 distinct clusters: pain-insomnia-fatigue, cognitive disturbance-outlook, and gastrointestinal. The pain-insomnia-fatigue and cognitive disturbance-outlook clusters were associated with individual characteristics, optimism, self-transcendence, and positive and negative mood. The gastrointestinal cluster correlated significantly only with positive mood. Conclusions: This study provides insight into symptoms that group together and the relationship of symptom clusters to antecedents and mood. Implications for Practice: These findings underscore the need to define and standardize the measurement of symptom clusters and understand variability in concurrent symptoms. Attention to symptom clusters shifts the clinical focus from a specific symptom to the patient’s experience as a whole and helps identify the most effective interventions.

Mediation and Moderation: Testing Relationships between Symptom Status, Functional Health, and Quality of Life in HIV Patients.

We extended Wilson and Clearys (1995) health-related quality of life model to examine the relationships among symptom status (Symptoms), functional health (Disability), and quality of life (QOL). Using a community sample (N = 956) of male HIV positive patients, we tested a mediation model in which the relationship between Symptoms and QOL is partially mediated by Disability. Common and unique ideas from 3 approaches to examining moderation of effects in mediational models (Edwards & Lambert, 2007; MacKinnon, 2008; Preacher, Rucker, & Hayes, 2007) were used to test whether (a) the direct relationship of Symptoms to QOL and (b) the relationship of Disability to QOL are moderated by age. In the mediation model, both the direct and the indirect (mediated) effects were significant. The direct relationship of Symptoms to QOL was significantly moderated by age, but the relationship of Disability to QOL was not. High Symptoms were associated with lower QOL at all ages, but this relationship became stronger at older ages. We compare the 3 approaches and consider their advantages over traditional approaches to combining mediation and moderation.

A theoretical approach to measuring quality of life.

The purpose of this article is to discuss conceptual issues surrounding health-related quality of life (HRQOL) and to provide an example of how structural equation modeling can address some of these conceptual issues. This article reports the development of the measurement model for overall quality of life, a dimension of HRQOL as conceptualized by Wilson and Cleary (1995). The sample (N = 1410) is from the AIDS Time-Oriented Health Outcome Study (ATHOS) databank, a longitudinal observational database of persons with HIV-associated illness. The hypothesized second-order factor model consists of 5 latent variables and 17 measured items. The fit indicators (RMSEA = .0717; SRMR = .0450; CFI = .951) suggest that the model provides an adequate description of the pattern of relationships in the data. A theoretical approach to HRQOL will expand its clinical use as an outcome measure and increase its relevance.

Documentation of care outcomes in an academic nursing clinic: an assessment.

PURPOSEnTo assess documentation of client data collected at an academic nursing clinic using the Wilson and Cleary Health Related Quality of Life (HRQOL) conceptual model as a framework.nnnDATA SOURCESnA chart audit of 100 randomly selected active client records was conducted.nnnCONCLUSIONSnAlthough several significant HRQOL variables were documented, data regarding general health perception and quality of life were not present. The HRQOL conceptual model provided an appropriate structure for evaluating the documentation. Further effort must be made to include key HRQOL dimensions in the clinics documentation system.nnnIMPLICATIONS FOR PRACTICEnDocumenting the quality of care provided in nursing clinics is essential in order for other professionals and the public to recognize nursing professionals as accountable and credible. This project formed the basis for a computerized outcomes-based client record system.

Confirmation of the validity of the HAQ-DI in two populations living with chronic illnesses.

The assessment of functional health in chronic illnesses such as HIV/AIDS and rheumatoid arthritis is central to the measurement of health-related quality of life. The purpose of this article is to report the testing and comparison of the measurement structure of the Health Assessment Questionnaire-Disability Index (HAQ-DI), a measure of functional health, in 917 persons living with HIV/AIDS and 901 individuals with rheumatoid arthritis. The samples come from data collected as part of the Arthritis, Rheumatism, and Aging Medical Information System (ARAMIS) and AIDS Time-Oriented Health Outcome Study (ATHOS) projects. Using confirmatory factor analysis (CFA), the hypothesized structure represented by a general factor (functional health) and eight measured items was tested separately. Based on the fit indexes, the model fit the ATHOS data (χ2 = 36.933, p < .0117; CFI = 1.000; SRMR = 0.025). After correlating the error terms for two of the measured items, the model also fit the ARAMIS data (χ2 = 302.34, p = .0000; CFI = 0.937; SRMR = 0.041). This analysis provides further support of the construct validity of the HAQ-DI for persons living with HIV/AIDS or rheumatoid arthritis.