Assessing Utility Where Short Measures Are Required: Development of the Short Assessment of Quality of Life-8 (AQoL-8) Instrument

Objectives:  As researchers seek to include clinical outcomes, the health-related quality of life (HRQoL) of participants and meet economic evaluation demands, they are confronted with collecting disparate outcome data where parsimony is imperative. This study addressed this through construction of a short HRQoL measure, the Assessment of Quality of Life (AQoL)-8 from the original AQoL.
Methods:  Data from the AQoL validation database (N = 996) were reanalyzed using item response theory (IRT) to identify the least fitting items, which were removed. The standard AQoL scoring algorithm and weights were applied. Validity, reliability, and sensitivity tests were carried out using the 2004 South Australian Health Omnibus Survey (N = 3015), including direct comparisons with other short utility measures, the EQ5D and SF6D.
Results:  The IRT analysis showed that the AQoL was a weak scale (Loevinger H = 0.36) but reliable (Mokken ρ = 0.84). Removal of the four weakest items led to an 8-item instrument with two items per subscale, the AQoL-8. The AQoL-8 Loevinger H = 0.38 and Mokken ρ = 0.80 suggested similar psychometric properties to the AQoL. It correlated (intraclass correlation coefficient) 0.95 (or 90% of shared variance) with the AQoL. The AQoL-8 was as sensitive to six common health conditions as the AQoL, EQ5D, and SF6D.
Conclusions:  The utility scores fall on the same life–death scale as those of the AQoL. Where parsimony is imperative, researchers may consider use of the AQoL-8 to collect participant self-report HRQoL data that is suitable for use either as reported outcomes or for the calculation of quality-adjusted life-years for cost-utility analysis.     

Quality of life assessment in the community-dwelling elderly: validation of the Assessment of Quality of Life (AQoL) Instrument and comparison with the SF-36

Measurement of Health-Related Quality of Life (HRQoL) of the elderly requires instruments with demonstrated sensitivity, reliability, and validity, particularly with the increasing proportion of older people entering the health care system. This article reports the psychometric properties of the 12-item Assessment of Quality of Life (AQoL) instrument in chronically ill community-dwelling elderly people with an 18-month follow-up. Comparator instruments included the SF-36 and the OARS. Construct validity of the AQoL was strong when examined via factor analysis and convergent and divergent validity against other scales. Receiver Operator Characteristic (ROC) curve analyses and relative efficiency estimates indicated the AQoL is sensitive, responsive, and had the strongest predicative validity for nursing home entry. It was also sensitive to economic prediction over the follow-up. Given these robust psychometric properties and the brevity of the scale, AQoL appears to be a suitable instrument for epidemiologic studies where HRQoL and utility data are required from elderly populations.     

An evaluation of the construct validity of the Developmental Test of Visual-Motor Integration using the Rasch Measurement Model

Background:  One method of evaluating the construct validity of instruments is the Rasch Measurement Model (RMM), an increasingly popular method used for test construction and validation.
Aim:  The aim was to examine the construct validity of the Developmental Test of Visual-Motor Integration 5th Edition (VMI) by applying the RMM to evaluate its scalability, dimensionality, differential item functioning and hierarchical ordering.
Method:  The participants were 400 children aged 5 to 12 years, recruited from six schools in Melbourne, Victoria, who completed the VMI under the supervision of an occupational therapist. VMI items 1, 2 and 3 were excluded from the Rasch analysis since all of the children achieved a perfect score on these items.
Results:  None of the items exhibited RMM misfit due to goodness-of-fit mean square (MnSq) infit statistics and standardised z (ZStd) scores being outside the specified acceptable range. VMI item 9 (copied circle) exhibited differential item functioning based on gender. In relation to hierarchical ordering of items, several were found to have similar logit difficulty values. For example, VMI items 26, 27 and 29; items 18, 22 and 24; and items 4, 5 and 11 were found to have the same level of challenge. As well, the VMI scale item logit measure order did not match that presented in the VMI test manual.
Conclusion:  Theoretically, the VMI items are developmentally ordered; however, this ordering was not mirrored by the item logit difficulty scores obtained. This has scoring implications, where scoring a respondent's VMI test booklet is terminated after three consecutive items are not passed. Clinicians should also be aware that item 9 may exhibit bias related to gender.     

Imputation of SF-12 health scores for respondents with partially missing data

OBJECTIVE: To create an efficient imputation algorithm for imputing the SF-12 physical component summary (PCS) and mental component summary (MCS) scores when patients have one to eleven SF-12 items missing. STUDY SETTING: Primary data collection was performed between 1996 and 1998. STUDY DESIGN: Multi-pattern regression was conducted to impute the scores using only available SF-12 items (simple model), and then supplemented by demographics, smoking status and comorbidity (enhanced model) to increase the accuracy. A cut point of missing SF-12 items was determined for using the simple or the enhanced model. The algorithm was validated through simulation. DATA COLLECTION: Thirty-thousand-three-hundred and eight patients from 63 physician groups were surveyed for a quality of care study in 1996, which collected the SF-12 and other information. The patients were classified as "chronic" patients if they reported that they had diabetes, heart disease, asthma/chronic obstructive pulmonary disease, or low back pain. A follow-up survey was conducted in 1998. PRINCIPAL FINDINGS: Thirty-one percent of the patients missed at least one SF-12 item. Means of variance of prediction and standard errors of the mean imputed scores increased with the number of missing SF-12 items. Correlations between the observed and the imputed scores derived from the enhanced models were consistently higher than those derived from the simple model and the increments were significant for patients with > or =6 missing SF-12 items (p<.03). CONCLUSION: Missing SF-12 items are prevalent and lead to reduced analytical power. Regression-based multi-pattern imputation using the available SF-12 items is efficient and can produce good estimates of the scores. The enhancement from the additional patient information can significantly improve the accuracy of the imputed scores for patients with > or =6 items missing, leading to estimated scores that are as accurate as that of patients with <6 missing items.     

Correlations between disease-specific and generic health status questionnaires in patients with advanced COPD: a one-year observational study

ABSTRACT: BACKGROUND: Longitudinal studies analyzing the correlations between disease-specific and generic questionnaires at different time points in patients with advanced COPD are lacking. The aim of this study was to determine whether and to what extent a disease-specific health status questionnaire (Saint George's Respiratory Questionnaire, SGRQ) correlates with generic health status questionnaires (EuroQol-5-Dimensions, EQ-5D; Assessment of Quality of Life instrument, AQoL; Medical Outcomes Study 36-Item Short-Form Health Survey, SF-36) at four different time points in patients with advanced COPD; and to determine the correlation between the changes in these questionnaires during one-year follow-up. METHODS: Demographic and clinical characteristics were assessed in 105 outpatients with advanced COPD at baseline. Disease-specific health status (SGRQ) and generic health status (EQ-5D, AQoL, SF-36) were assessed at baseline, four, eight, and 12 months. Correlations were determined between SGRQ and EQ-5D, AQoL, and SF-36 scores and changes in these scores. Agreement in direction of change was assessed. RESULTS: Eighty-four patients (80%) completed one-year follow-up and were included for analysis. SGRQ total score and EQ-5D index score, AQoL total score and SF-36 Physical Component Summary measure (SF-36 PCS) score were moderately to strongly correlated. The correlation of the changes between the SGRQ total score and EQ-5D index score, AQoL total score, SF-36 PCS, and SF-36 Mental Component Summary measure (SF-36 MCS) score were weak or absent. The direction of changes in SGRQ total scores agreed slightly with the direction of changes in EQ-5D index score, AQoL total score, and SF-36 PCS score. CONCLUSIONS: At four, eight and 12 months after baseline, SGRQ total scores and EQ-5D index scores, AQoL total scores and SF-36 PCS scores were moderately to strongly correlated, while SGRQ total scores were weakly correlated with SF-36 MCS scores. The correlations between changes over time were weak or even absent. Disease-specific health status questionnaires and generic health status questionnaires should be used together to gain complete insight in health status and changes in health status over time in patients with advanced COPD.     

A simple imputation algorithm reduced missing data in SF-12 health surveys

OBJECTIVE: The SF-12 Health Survey is a 12-item questionnaire that yields two summary scores (physical and mental health). Neither score can be computed when an item is missing. We explored imputation methods for missing scores for this instrument. STUDY DESIGN AND SETTING: Using data from a population-based survey, we tested several ways of imputing simulated missing data. RESULTS: Among 1250 participants, 118 (9.6%) had at last one missing SF-12 item. Missing data were more common among women, older respondents, non-Swiss nationals, and health service users. Among the 1132 respondents with complete data, replacement of any item with the mean population item weight yielded good results: the mean correlation between imputed and true score was 0.979 for both the physical and mental score. Results remained satisfactory when up to three of the six key items for each score (items that contribute predominantly to a given score), and any number of non-key items, were replaced by the mean. Application of this imputation algorithm to the original survey reduced the proportion of missing scores to <1%. Respondents with incomplete surveys, hence imputed scores, had lower scores than respondents with complete data (physical score: 44.9 vs. 49.8, p < 0.001, mental score: 44.4 vs. 46.3, p=0.064). CONCLUSIONS: A simple imputation algorithm can substantially reduce the proportion of missing scores for the SF-12 health survey, and consequently reduce non-response bias.     

Application of Rasch analysis in health care is increasing and is applied for variable reasons in mobility instruments

ObjectiveTo identify the frequency of Rasch analysis use in health instrument development or refinement and the characteristics of Rasch application in mobility scales.Study Design and SettingThe entire databases of Medline, CINAHL, PEDro, EMBASE, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews were searched until January 2009. Articles that reported the development or refinement of health instruments using Rasch analysis were included. Of the 234 articles that met inclusion, 10 were categorized as “mobility” instruments. Data were extracted relating to each instrument and the use of Rasch analysis in the development or refinement of the instruments.ResultsThe number of articles reporting the use of Rasch analysis of health instruments is increasing, from 1 article in 1987 to 48 articles in 2007. Of the 10 mobility instruments examined, the primary reason Rasch was used varied. Reasons included assessing instrument unidimensionality, differential item functioning, rating categories, item hierarchy, and redundant items.ConclusionThe application of Rasch analysis in health instrument development has markedly increased in recent years. However, few mobility instruments have been developed or refined using Rasch analysis. The reasons that the Rasch model was used varied across mobility instruments.     

The effect of different methods of collecting data: Mail,telephone and filter data collection issues in utility measurement

When collecting data researchers can interview participants, conduct telephone interviews, or mailout questionnaires. Often mixed methods are used. Whether these methods produce equivalent data is under-researched in the health-related quality of life (HRQoL) field. In addition, the effect of using filter questions has not been researched among HRQoL multi-attribute utility instruments. This study randomly sampled from Melbourne, Australia, and employed a test–retest design to investigate whether mail or telephone interview made any difference to Assessment of Quality of Life (AQoL) instrument utility scores. A filter question AQoL version investigated the effect of filters on scores. There was no significant difference in standard AQoL scores between mail self-completion and telephone interview, regardless of which was administered first. Inclusion of filter questions encouraged respondents to select the best response category thereby screening out minor health conditions. The effect was to increase utility scores by 0.06 or 7%. This effect has not been previously reported in utility instruments and has profound implications for economic evaluations using cost-utility analysis; there are implications for researchers using filter questions in general. In conclusion, researchers should feel confident that utility scores elicited from the standard AQoL through self-completion mail and telephone interview administrations are directly comparable.     

Measurement Qualities of a Self-Report and Therapist-Scored Functional Capacity Instrument Based on the Dictionary of Occupational Titles

Studies provide convincing arguments to support the development of functional capacity instruments based on the Dictionary of Occupational Titles (DOT). The purpose of this study is to investigate the item-level measurement qualities of a newly developed DOT-based functional capacity instrument for clients undergoing rehabilitation treatment for back pain. Client and therapist ratings were collected on 124 clients from 27 rehabilitation sites using the newly developed Occupational Rehabilitation Data Base (ORDB) functional capacity instrument. Rasch analysis was used to investigate: (1) unidimensionality, (2) hierarchical item difficulty continuum, (3) rater severity, and 4) person-item match. Overall, the functional capacity scale of the ORDB showed good measurement qualities. All items, except the Handling item fit the Rasch measurement model. Because of high fit statistics and loading on factors independent from the remainder of the items, the "handling" item was removed, from further analyses. Separate client-rated and therapist-rated instruments retained good item-level psychometrics. While client and therapist items showed similar item-difficulty hierarchical structures, clients had a tendency to be more severe in their rating and the correlation between client and therapist ratings was relatively low, 0.32. These findings suggest that Handling items should not be included as a DOT measure for clients with back pain. While the above psychometric study supports using client or therapist ratings as independent instruments, the lack of concordance between these ratings requires further investigation.     

A view from the bridge: agreement between the SF-6D utility algorithm and the Health Utilities Index

BACKGROUND: The SF-6D is a new health state classification and utility scoring system based on 6 dimensions ('6D') of the Short Form 36, and permits a "bridging" transformation between SF-36 responses and utilities. The Health Utilities Index, mark 3 (HUI3) is a valid and reliable multi-attribute health utility scale that is widely used. We assessed within-subject agreement between SF-6D utilities and those from HUI3. METHODS: Patients at increased risk of sudden cardiac death and participating in a randomized trial of implantable defibrillator therapy completed both instruments at baseline. Score distributions were inspected by scatterplot and histogram and mean score differences compared by paired t-test. Pearson correlation was computed between instrument scores and also between dimension scores within instruments. Between-instrument agreement was by intra-class correlation coefficient (ICC). RESULTS: SF-6D and HUI3 forms were available from 246 patients. Mean scores for HUI3 and SF-6D were 0.61 (95% CI 0.60-0.63) and 0.58 (95% CI 0.54-0.62) respectively; a difference of 0.03 (p<0.03). Score intervals for HUI3 and SF-6D were (-0.21 to 1.0) and (0.30-0.95). Correlation between the instrument scores was 0.58 (95% CI 0.48-0.68) and agreement by ICC was 0.42 (95% CI 0.31-0.52). Correlations between dimensions of SF-6D were higher than for HUI3. CONCLUSIONS: Our study casts doubt on the whether utilities and QALYs estimated via SF-6D are comparable with those from HUI3. Utility differences may be due to differences in underlying concepts of health being measured, or different measurement approaches, or both. No gold standard exists for utility measurement and the SF-6D is a valuable addition that permits SF-36 data to be transformed into utilities to estimate QALYs. The challenge is developing a better understanding as to why these classification-based utility instruments differ so markedly in their distributions and point estimates of derived utilities.     

The SF-12 in the Australian population: cross-validation of item selection

OBJECTIVE: To cross-validate the selection of the questionnaire items for the SF-12 in an Australian sample. METHOD: The sample comprised respondents with complete data on the SF-36 summary measures and the 12 items that comprise the SF-12 (n = 17,671) from the 1995 Australian National Health Survey. Two sets of mental and physical summary scales were analysed, based on either scoring from Australian normative data or the standard United States normative data scoring. Forward stepwise linear regression analyses of weighted data provided the proportion of variance in the summary scales explained by the SF-12 items. RESULTS: The SF-12 items predicted at least 90% of the variance in both the physical and mental summary scales of the SF-36, whether they were scored with Australian or United States normative data. Implications: The SF-12 is an appropriate substitute for the SF-36 when the summary scales are of interest but a briefer instrument is required.     

Measuring everyday functional competence using the Rasch assessment of everyday activity limitations (REAL) item bank

Objective

Traditional patient-reported physical function instruments often poorly differentiate patients with mild-to-moderate disability. We describe the development and psychometric evaluation of a generic item bank for measuring everyday activity limitations in outpatient populations.

Study design and setting

Seventy-two items generated from patient interviews and mapped to the International Classification of Functioning, Disability and Health (ICF) domestic life chapter were administered to 1128 adults representative of the Dutch population. The partial credit model was fitted to the item responses and evaluated with respect to its assumptions, model fit, and differential item functioning (DIF). Measurement performance of a computerized adaptive testing (CAT) algorithm was compared with the SF-36 physical functioning scale (PF-10).

Results

A final bank of 41 items was developed. All items demonstrated acceptable fit to the partial credit model and measurement invariance across age, sex, and educational level. Five- and ten-item CAT simulations were shown to have high measurement precision, which exceeded that of SF-36 physical functioning scale across the physical function continuum. Floor effects were absent for a 10-item empirical CAT simulation, and ceiling effects were low (13.5%) compared with SF-36 physical functioning (38.1%). CAT also discriminated better than SF-36 physical functioning between age groups, number of chronic conditions, and respondents with or without rheumatic conditions.

Conclusion

The Rasch assessment of everyday activity limitations (REAL) item bank will hopefully prove a useful instrument for assessing everyday activity limitations. T-scores obtained using derived measures can be used to benchmark physical function outcomes against the general Dutch adult population.

     

Population norms and meaningful differences for the Assessment of Quality of Life (AQoL) measure

OBJECTIVE: The Assessment of Quality of Life (AQoL) instrument is widely used in Australian health research. To assist researchers interpret and report their work, this paper reports population and health status norms, general minimal important differences (MIDs) and effect sizes. METHOD: Data from the 1998 South Australian Health Omnibus Survey (n=3,010 population-based respondents) were analysed by gender, age group and health status. Data from four other longitudinal studies were analysed to obtain estimated MIDs. RESULTS: The mean (SD) AQoL utility score was 0.83 (0.20). Gender and age subgroup differences were apparent; the mean scores for women were consistent until their 50s, when scores declined. Greater variability was observed for males whose scores declined more slowly but consistently between 40-80 years. For both genders, those aged 80+ years had the lowest scores. When assessed by health status, those reporting excellent health obtained the highest utility scores; progressive declines were observed with decreasing health status. Effect sizes of 0.13 or greater may reflect important differences between groups. A difference in AQoL scores of 0.06 utility points over time suggests a general MID. CONCLUSIONS: AQoL population norms, MIDs and effect sizes can be used as reference points for the interpretation of AQoL data. These findings add to the growing evidence that the AQoL is a robust and sensitive measure that has wide applicability. Implications: The availability of population norms will assist researchers using the AQoL to more easily interpret and report their work.     

Development of a short osteoporosis quality of life questionnaire by equating items from two existing instruments.

This study aimed to develop a short Osteoporosis-Specific Quality of Life Questionnaire based on the assemblage (equating) of the items of two existing questionnaires (OQLQ and QUALEFFO). For this purpose, each questionnaire was administered by random assignment to a different group of female patients (OQLQ, n = 172; QUALEFFO, n = 166) with vertebral fractures due to osteoporosis. A common anchor test (SF-36) was also given to both groups. Seven different sets of OQLQ-QUALEFFO common items were defined by inspecting their own correlation with the scores of the eight dimensions of the SF-36. Within each set, equating consisted in connecting the OQLQ and QUALEFFO through their link with the SF-36. Equating was carried out through the Rasch mathematical model. Quantitative (item statistics) and qualitative reductions (expert opinion) of the equated sets resulted in a 16-item questionnaire. Although the new instrument requires further empirical validation, it provides a promising alternative to currently existing longer questionnaires for use in clinical practice.     

Mapping from Disease-Specific Measures to Utility: An Analysis of the Relationships between the Inflammatory Bowel Disease Questionnaire and Crohn''s Disease Activity Index in Crohn''s Disease and Measures of Utility

OBJECTIVES: To examine the relationship between the Inflammatory Bowel Disease Questionnaire (IBDQ), Crohn's Disease Activity Index (CDAI) and measures of utility (EQ-5D and the SF-6D indexes), and to estimate algorithms to map the two utility values from IBDQ and CDAI scores. METHODS: A large data set from clinical trials in Crohn's disease provided contemporaneous patient responses to all four questionnaires. Paired observations from multiple time-points were analyzed. We calculated mean utility scores by IBDQ and CDAI score deciles; Spearman correlation coefficients for paired observations between IBDQ and EQ-5D (n = 3320) and IBDQ and SF-6D (n = 3230), and explored regression models using maximum likelihood estimation. The IBDQ/SF-6D model was validated against paired observations from an independent data set. RESULTS: The IBDQ decile analysis demonstrated a consistent positive relationship with both utility indexes. Correlations between the IBDQ and both the EQ-5D and SF-6D were statistically significant (P < 0.0001), with correlation coefficients of 0.76 and 0.85, respectively. A simple linear model between EQ-5D and IBDQ explained 45% of the variance. The residuals plot for the IBDQ/SF-6D model suggested some nonlinearity and a nonlinear model explained 69% of the variance. In the validation analysis, no statistically significant difference was observed between the mean observed SF-6D and the SF-6D scores estimated using the IBDQ/SF-6D regression model. CONCLUSIONS: Given the strength, consistency, and predictable characteristics of the relationships, the algorithms appear to provide valuable and valid methods to estimate utilities from IBDQ scores (but not CDAI) in trials of Crohn's disease patients that have collected IBDQ scores but not utilities.     

The SF-36 physical and mental health factors were confirmed in cancer and HIV/AIDS patients

BACKGROUND AND OBJECTIVE: This study assesses the extent to which the RAND-36/SF-36 items measure physical and mental health (PH and MH), as implied by existing summary scoring systems. METHODS: A total of 1,714 heterogeneous cancer and HIV/AIDS patients were recruited from five institutions. Of these, 56% were women; 81% Caucasians; and about 10% were from each of the major cancer types and HIV/AIDS. RESULTS: Analyses of the SF-36 confirmed the two dimensions of health namely physical and mental. However, item fit statistics and residual factor analysis revealed that some items intended to represent the PH dimension fit better with the MH dimension. CONCLUSION: This paper demonstrated the value of Rasch residual factor analysis for understanding and enhancing interpretation of health.     

Relationship between health status and utility measures in older claudicants

The purpose of this study was to examine the relationship between health status and health utility measures in 34 older claudicants and to determine which attributes of health status were significant predictors of health state valuation/preference. The MOS SF-36 was used to assess health status and the rating scale and multiattribute Health Utility Index (HUI) were used to assess utility scores. With regard to health status, the bodily pain and physical functioning subscales contributed the most to reductions in quality of life (QoL) with mean subscale scores substantially lower than reported population norms. Patients rated their health status approximately one-third below a state of perfect health on both utility measures. Moderate correlations were observed between the MOS SF-36 subscale scores and the HUI and rating scale scores. In multivariable regression models, physical functioning and mental health were the best predictors of HUI scores, whereas general health and vitality were the best predictors of rating scale scores. Approximately 50% of the variance in utility scores was explained by these attributes. This study provides further documentation that bodily pain and reductions in physical function contribute to reductions in QoL in older patients with intermittent claudication. Other attributes of health status, however, notably psychological distress, were predictive of patients' preference for health states. Recognized constructs of physical and mental health explained the substantial variation in the utility/preference assessment in this population. Furthermore, these data are consistent with those reported in the Dutch Iliac Stent Trial.     

Chinese SF-36 Health Survey: translation,cultural adaptation,validation, and normalisation

STUDY OBJECTIVE: To develop a self administered Chinese (mainland) version of the Short-Form Health Survey (SF-36) for use in health related quality of life measurements in China. DESIGN: A three stage protocol was followed including translation, tests of scaling construction and scoring assumptions, validation, and normalisation. SETTING: 1000 households in 18 communities of Hangzhou. PARTICIPANTS: 1688 respondents recruited by multi-stage mixed sampling. Main results: The assumption of equal intervals was violated for the vitality and mental health scales. The recoded item values were used to calculate scale scores. The clustering and ordering of item means was the same as that of the source and other two Chinese versions. The items in each scale had similar standard deviations except those in the physical functioning, boduily pain, social functioning scales. The item hypothesised scale correlations were identical for all except the social functioning and vitality scales. Convergent validity and discriminant validity were satisfactory for all except the social functioning scale. Cronbach's alpha coefficients ranged from 0.72 to 0.88 except 0.39 for the social functioning scale and 0.66 for the vitality scale. Two weeks test-retest reliability coefficients ranged from 0.66 to 0.94. Factor analysis identified two principal components explaining 56.3% of the total variance. The Chinese SF-36 could distinguish known groups. CONCLUSIONS: This study suggested that the Chinese (mainland) version of the SF-36 functioned in the general population of Hangzhou, China quite similarly to the original American population tested. Caution is recommended in the interpretation of the social functioning and vitality scales pending further studies.     

A Rasch and factor analysis of a Paramedic Graduate Attribute scale

This study examined the construct validity of the Paramedic Graduate Attribute scale (PGAS) using factor analysis and Rasch Analysis. A convenience sample was used in the study involving paramedics from all states and territories in Australia. Participants were asked to rate the importance of 47 graduate attribute items. Principal components analysis (PCA) was undertaken on the 47 items followed by Oblique Oblimin rotation. For the Rasch analysis item fit, item invariance and dimensionality were examined. A total of 872 paramedics participated in the study (23% response rate). PCA of the 47 items revealed seven factors with eigenvalues greater than 1, accounting for 40.6% of the total variance. The subsequent Rasch analyses based on the seven factors produced seven misfitting items and confirmed a 7-factor solution. The 7-factor PGAS produced a good fit to the Rasch Model and exhibited good reliability and unidimensionality, offering the Australian paramedic discipline a set of empirically based graduate attributes.