The PROMIS item banks were administered via web-based survey to a national internet panel maintained by Polimetrix (now YouGovPolimetrix; see http://www.polimetrix.com). The field test involved administering the item banks from five domains (i.e., pain, fatigue, physical functioning, social activities, emotional distress) to selected participants . Some respondents were randomly assigned to administer different complete item banks, that is, all the items within a defined domain-specific bank, such as physical function or fatigue. Other respondents were randomly assigned to block-form item samples consisting of sets of seven consecutive items from each of 14 subdomains in the five PROMIS health domains.
The PROMIS sample was selected to be generally comparable to distributions of gender, age groups, race/ethnicity (white/African–American/Hispanic/other), and education (high school or less versus more than high school) based on the 2000 US census data (Liu et al., submitted). Study participants were identified from the Polimetrix internet panel and from selected clinical research centers. For the current study, the participants included subjects who administered the full item banks and the block data.
Wave 1 sample
Because of the number of item banks being tested in Wave 1, a complex data-collection strategy was employed. This strategy included two arms and a total sample size of 21,133. A total of 19,601 subjects were recruited by Polimetrix, with the remaining 1,532 subjects recruited by PROMIS research sites (Fig. 1). In the full-bank testing arm, 7,005 persons from the general population were administered two of the 14, 56-item, subdomain-specific PROMIS item banks. In the block testing arm, 14,128 individuals administered randomly selected seven-item blocks measuring each of the 14 PROMIS-targeted subdomains. The PROMIS research sites and the Polimetrix sample included both community and clinical samples. The clinical samples included persons with heart disease (n = 1,156), cancer (n = 1,754), rheumatoid arthritis (n = 557), osteoarthritis (n = 918), psychiatric disorders (n = 1,193), COPD (n = 1,214), spinal cord injury (n = 531), and other conditions (n = 560).
The EQ-5D is a preference-based instrument designed to measure generic health status across five dimensions of health: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, with three response levels (no problems, some problems, extreme problems) . A unique EQ-5D health state is defined by combining one level from each of the five dimensions, and scores range from −0.109 to 1.0, with greater scores indicating better overall health. The calculation of the EQ-5D index scores was based on the valuation reported by Shaw et al.  that was derived from a large-scale survey of the US general population . The EQ-5D also includes a single visual analogue scale (EQ-5D VAS) that was not used in this study.
PROMIS global items
The PROMIS survey included ten global health items (Hays et al. submitted). One item was the general health question rating overall health on a poor-to-excellent scale. The remaining items covered quality of life, mental health, physical health (two items), pain, fatigue, social function (two items), and emotional distress. Based on these global items, Hays et al. (submitted) found evidence supporting two summary scores assessing physical and mental health. Mental health and physical health summary scores were developed from global items in factor and item response theory analyses conducted in the PROMIS Wave 1 sample. The PROMIS global items were administered to all participants in the Wave 1 sample (Fig. 1). The summary scores were calculated as sums of the relevant individual global items, and individual global item scores (untransformed) were included in the subsequent regression analyses.
Domain item banks
The PROMIS initial item banks were developed based on the published literature, clinician review, and qualitative research on patients with various health conditions (for more information, go to http://www.nihpromis.org). Existing domain-specific instruments were also reviewed for item content, and new items were developed for the PROMIS item banks [19, 20]. Content of the final set of physical function, fatigue, pain impact, anxiety, and depression items was revised based on the results of cognitive debriefing interviews . For this study, we used the calibrated and available item banks measuring physical function, fatigue, pain impact, anxiety, and depression (www.nihpromis.org). The physical function item bank covered self-reported capability for upper extremity and lower extremity function. The fatigue bank was developed to cover both fatigue experience and impact. The pain impact domain included items on various impacts of pain on daily activities and function. The anxiety bank included various symptoms associated with anxiety, and the depression bank included items on depressed mood. Each item used a five- to six-level categorical response scale. The domain scores included in this analysis are T-scores derived from Theta scores from the item response theory calibrations. For the physical function domain scores, higher scores indicate better physical functioning. For the fatigue, pain impact, anxiety, and depression domain scores, higher scores indicate more severe impairment.
Information on demographic characteristics was collected for the study participants (i.e., age, gender, race/ethnicity, education). Information was also collected on a number of chronic medical conditions in the Wave 1 sample. These chronic conditions were classified into groups of physical and mental health disorders.
A series of ordinary least squares (OLS) regression models were specified where EQ-5D index scores were predicted from different sets of PROMIS scores. First, three sets of regression models were performed using (1) all ten global items; (2) a subset of eight global items (reduced because of multicollinearity); and (3) a subset of eight global items (using alternative duplicative items). The Wave 1 analysis sample of 20,400 cases was separated into two randomly assigned split-half samples; the models were developed in the first sample and the analyses replicated in the second sample to confirm results. Second, we specified an OLS regression model using the PROMIS global item–based mental health and physical health summary scores to predict EQ-5D index scores in the block testing sample (n = 14,128). Finally, a regression analysis was performed including the T-scores for the PROMIS domain item banks for physical function, fatigue, pain impact, anxiety, and depression using the block design data. We selected these five domain banks because they (1) covered important patient-reported outcome constructs, including mental health and physical health; and (2) these item banks were calibrated and tested within the PROMIS project. Subjects were included in this analysis if they completed at least three items for each of the five relevant PROMIS domains and had an EQ-5D index score (n = 1,658). The domain scores included in this analysis are T-scores derived from Theta scores from the item response theory calibrations.
We examined plots of residuals from the regression analyses and performed a Bland-Altman assessment of agreement  comparing the actual and predicted EQ-5D index scores. A range of agreement was defined as mean bias ± 2 standard deviation (SD) units. Intraclass correlation coefficients (ICCs) were calculated comparing actual and predicted EQ-5D scores.
Estimated EQ-5D index scores were also compared with actual EQ-5D scores based on the PROMIS general population sample by gender and age groups and by type of chronic medical condition (n = 2,722; Liu et al. submitted). In addition, we compared the PROMIS estimated EQ-5D index scores to those reported in the Luo et al.  and Fryback et al.  studies by gender and age groups.