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Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. ROLE OF THE STUDY SPONSOR
  9. REFERENCES
  10. Supporting Information

Objective

To assess the reliability and criterion and construct validity of the self-administered Brief Index of Lupus Damage (SA-BILD), a patient-reported measure of organ damage in systemic lupus erythematosus (SLE).

Methods

The validity of the SA-BILD was assessed using data from the Georgians Organized Against Lupus (GOAL) survey. GOAL is a longitudinal cohort of SLE patients predominantly derived from the Georgia Lupus Registry, a population-based registry established in Atlanta, Georgia. In total, 711 participants with documented SLE completed the SA-BILD. To test reliability, the SA-BILD was readministered to 32 patients. Criterion validity was examined in 150 respondents for whom the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) was also completed. Construct validity was assessed among 711 GOAL participants by dividing the SA-BILD scores into quartiles and examining the association with demographics, health status, and health care utilization.

Results

The test–retest correlation score was 0.93 (P < 0.0001), the item-by-item agreement with the SDI was >80% for most SA-BILD items, and the Spearman's rho correlation coefficient for the SDI and SA-BILD was moderately high (ρ = 0.59, P < 0.0001). SA-BILD scores showed significant associations in the expected directions with age, disease duration, disease activity, overall health, comorbidity index, and physician visits.

Conclusion

The SA-BILD was reliable and had very good or good criterion validity compared with the SDI when tested in a predominantly African American cohort of US SLE patients. Associations of SA-BILD scores with sociodemographics and health status were consistent with previous studies. These findings support the use of the SA-BILD as a valid measure of patient-reported damage in SLE.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. ROLE OF THE STUDY SPONSOR
  9. REFERENCES
  10. Supporting Information

As the life expectancy of patients with systemic lupus erythematosus (SLE) has improved in past decades, comorbid conditions have become important determinants of outcomes. SLE patients are frequently affected by irreversible organ damage that can occur as a consequence of disease activity, disease-related chronic inflammation, and/or side effects of the drugs used to treat the disease ([1-4]). Quantifying organ damage of SLE populations has therefore become a relevant dimension of outcomes research ([1, 4-10]).

Damage is most commonly assessed with the validated Systemic Lupus International Collaborating Clinics/American College of Rheumatology (ACR) Damage Index (SDI) ([1, 11-13]). The SDI has been found to predict mortality ([5, 7, 8, 14]), physical function ([15, 16]), work disability ([17, 18]), health care utilization ([19, 20]), and societal burden ([21]). In its original form, this 41-item questionnaire was to be completed by a trained physician ([12, 13]); however, the need to expand the available SDI tool to assess SLE-related damage with a patient-reported measure arose along with the development of community-based cohorts. Efforts led by investigators from academic centers in the US resulted in 2 validated instruments originating from the SDI: the Lupus Damage Index Questionnaire (LDIQ) and the Brief Index of Lupus Damage (BILD) ([22, 23]). The LDIQ consists of 56 questions administered as a written survey; the BILD was designed to be a shorter patient-reported tool (28 questions) administered by an interviewer with SLE patients over the telephone or in person.

A preliminary validation study found that the BILD was a suitable proxy of the SDI ([23]). The BILD was highly acceptable to respondents and was administered efficiently by telephone interview. The criterion validation of the BILD was conducted with a relatively small sample of predominantly young, nonwhite patients from 2 university-affiliated SLE clinics, while the construct validity was analyzed with data from the Lupus Outcomes Study (LOS), a community-based cohort of predominantly middle-class, well-educated SLE patients, 66% of whom were non-Hispanic white ([23]).

Because SLE patients from minority groups have worse disease outcomes, having a cost-effective tool to quantify organ damage in patients from vulnerable groups is essential to better understand the burden of the disease at the population level. However, these groups are typically underrepresented in measure development and validation research. The promising validity findings of the BILD, along with the low administrative burden and high acceptability by LOS patients, encouraged us to adapt the BILD as a self-administered written version that could be mailed to SLE patients with diverse sociodemographic backgrounds. Herein, we describe the adaptation of the BILD to a self-administered format (SA-BILD) and assess its reliability and criterion and construct validity in a large SLE cohort from the Southeastern US that included a representative proportion of high-risk individuals.

Box 1. Significance & Innovations

  • Although having validated tools to measure patient-reported outcomes among vulnerable groups with systemic lupus erythematosus (SLE) is essential to better understand the burden of the disease at the population level, disadvantaged SLE groups are typically underrepresented in measure development and validation research.
  • We validated a self-administered patient-reported tool to quantify organ damage in a unique population-based cohort of SLE patients from the Southeastern US, which included a representative proportion of high-risk SLE individuals.
  • Our findings support the use of a novel cost-effective tool for collecting patient-reported damage for epidemiologic SLE research when physician assessment is not feasible.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. ROLE OF THE STUDY SPONSOR
  9. REFERENCES
  10. Supporting Information

Study population

Data from the Georgians Organized Against Lupus (GOAL) cohort were used to assess the reliability and criterion and construct validity of the SA-BILD. GOAL encompasses a large cohort of adult English-speaking SLE patients from metropolitan Atlanta, Georgia. The overall aim of GOAL is to examine the impact of sociodemographic and health care factors on outcomes that are relevant to patients, health care providers, and policy makers. Recruitment and data collection methods as well as the sociodemographic characteristics of SLE participants have been previously described ([24]). Briefly, the primary source of SLE enrollees is the Georgia Lupus Registry (GLR), a population-based registry funded by the Centers for Disease Control and Prevention in order to better estimate the incidence and prevalence of SLE in Atlanta, an area with a large number of African Americans at high risk for SLE ([25]). The GLR was implemented through a partnership between the Georgia Department of Public Health and Emory University; the Georgia Department of Public Health enabled Emory University investigators to review medical records without patient consent to meet the public health goal of determining the incidence and prevalence of lupus (under the Health Insurance Portability and Accountability Act Privacy Rule, 45 Code of Federal Regulations, parts 160 and 164). Furthermore, the Georgia Department of Public Health allowed Emory University investigators to recruit SLE patients into the GOAL cohort. Therefore, adult lupus patients who received medical care at community- and university-based practices were recruited by mail, by telephone, and in person to complete annual self-administered surveys. Over 70% of lupus patients in the GOAL cohort were derived from the GLR. Other patients came from the lupus clinics at Emory University, the indigent care hospital in Atlanta (Grady Memorial Hospital), and community rheumatologists from metropolitan Atlanta. There were 850 participants with a documented diagnosis of SLE; 688 fulfilled ≥4 revised ACR criteria for the classification of SLE and 162 fulfilled 3 ACR criteria and had a diagnosis of SLE by the attending board-certified rheumatologist ([26]).

The Emory University Institutional Review Board, Grady Health System Research Oversight Committee, and Georgia Department of Public Health Institutional Review Board approved the GOAL study protocol. All GOAL participants provided informed consent.

Data collection

Data for GOAL are collected through annual surveys that include questions on sociodemographic characteristics, health care utilization, and validated measures of health status, disease activity, and comorbidities. Given the high proportion of socioeconomically disadvantaged subjects in the GOAL cohort, the GOAL survey was designed for a population with limited health literacy and targeted an eighth-grade reading level. Additionally, we offered flexible administration modes (self- or interviewer-administered GOAL surveys) and delivery methods (mail, telephone, or in person). Among the 751 SLE respondents to the baseline GOAL survey, 711 completed the written survey (primarily by mail). The remaining 40 participants chose to complete GOAL surveys by telephone interview and were not included in this study. Sociodemographic and clinical characteristics were similar between respondents to the mail- and telephone-based survey, with the exception of disease duration, which was significantly shorter for respondents to the written survey (mean ± SD 13.3 ± 9.0 years) than for the group interviewed by telephone (mean ± SD 16.8 ± 8.0; data not shown). No significant differences were found between survey respondents (n = 751) and nonrespondents (n = 99) in sociodemographic and clinical characteristics.

SA-BILD

The original BILD was designed for administration by telephone interview. The description of the development and validation of the BILD has previously been published ([23]). In order to adapt the 28-question BILD tool to a self-administered form, we used the same table-based format as the other instruments included in the GOAL survey. To reduce a potential high rate of unknown answers, we adopted an approach similar to the LDIQ, providing only a yes or no response for each item ([22]). As in the LDIQ, after a brief introduction on the purpose of the questionnaire, we added the following: “don't worry if there are some medical words you don't understand. This usually means that you don't have the problem the question is asking about.” Additionally, to enhance the understanding of each question by readers of the SA-BILD (as opposed to listeners of the original BILD), we integrated into the questions or added in parentheses the optional notes of the original BILD. The SA-BILD was then piloted among 5 adult women with SLE from the Grady Lupus Clinic targeting wide age and education attainment. The patients' feedback on the clarity and the meaning of the questions and the appropriateness of the response choices served to revise the questionnaire. The only modification needed was the addition of a note to clarify that transient ischemic attack is not included as a positive response for stroke (item 5). The SA-BILD was then included into the baseline GOAL survey and mailed to a subset of 247 SLE patients. After the responses were evaluated, questions related to premature gonadal failure (only for women) were moved to the end of the table in order to reduce potential missing responses by men of 2 items originally placed at the bottom: diabetes mellitus and malignancy. The annual GOAL survey with the final SA-BILD was then mailed to the remaining GOAL participants. Like the original telephone form, the SA-BILD contained 28 questions that captured information on 26 of the original SDI items (see Supplementary Appendix A, available in the online version of this article at http://onlinelibrary.wiley.com/doi/10.1002/acr.22231/abstract).

Statistical analysis

Reliability was tested among 32 patients who completed the SA-BILD survey 2 times between December 2011 and June 2012. Spearman's rho correlation coefficients were used to measure test–retest reliability.

Criterion validity was examined in 150 consecutive SA-BILD respondents with SLE who had a followup visit at the Grady Health System–affiliated lupus clinic (n = 93) or the Emory University–affiliated lupus clinic (n = 57) within 6 months of the annual GOAL survey completion date. Between February and June 2012, staff rheumatologists completed the SDI blinded to the subjects' SA-BILD responses. We compared the SA-BILD item responses to the corresponding SDI responses by calculating the item-by-item percent-observed agreement (po) with the SDI. The prevalence-adjusted bias-adjusted kappa (PABAK; 2po − 1) has been proposed as a better measure of agreement than kappa when prevalence varies or when the prevalence of each method or instrument differs ([27]). Like kappa, a PABAK value of −1 indicates perfect disagreement, 0 indicates no agreement, and 1 indicates perfect agreement. We also compared the distributions of the overall SDI and SA-BILD scores, calculating the Spearman's rho correlation coefficients between both measures.

Construct validity was assessed using GOAL data collected by July 31, 2012. Because SA-BILD scores did not show a normal distribution, we divided the GOAL sample into quartiles based on SA-BILD scores to examine the correspondence of SA-BILD scores with demographics, disease duration, health-related measures, and health care utilization, which are measures previously associated with SDI disease damage. For demographic measures, we included age, sex, ethnicity (African American versus white), education (high school or less versus some college education or greater), annual household income below the federal poverty threshold (adjusted for the number of individuals in the household), and work status. Disease and health status measures included the Systemic Lupus Activity Questionnaire (SLAQ) ([28]), the Medical Outcomes Study Short Form 12 health survey ([29]), and the Rheumatic Diseases Comorbidity Index ([30]). We assessed the annual mean number of outpatient visits (to rheumatologists and to all physicians) over the past year as measures of health care utilization. We used the Cochran-Armitage trend test to compare the distribution of categorical measures across quartiles of the SA-BILD ([31, 32]). Likewise, we compared continuous measures using analysis of variance. Additionally, to explore the independent association of the sociodemographic measures with the SA-BILD, we modeled the SA-BILD score as a function of age, disease duration, sex, ethnicity, education, and employment. We used logistic regression and multiple regression analyses to test the SA-BILD score as binary (≥4 versus 0, 2–3 versus 0, or 1 versus 0) and continuous (raw score) variables, respectively. Response rates for individual items were used as a proxy for acceptability.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. ROLE OF THE STUDY SPONSOR
  9. REFERENCES
  10. Supporting Information

All SLE patients who responded to the self-administered GOAL survey (n = 711) completed the SA-BILD. Figure 1 shows the subsets of GOAL respondents examined for the different validation assessments.

image

Figure 1. Schematic diagram of Georgians Organized Against Lupus participants included in the self-administered Brief Index of Lupus Damage (BILD) validation assessments. SLE = systemic lupus erythematosus.

Download figure to PowerPoint

The sociodemographic and health characteristics of the SA-BILD participants and the subset examined for criterion validity are shown in Table 1. Among the 711 respondents to the SA-BILD, 94% were women and 78% were African American (Table 1); 35% attained a high school education or less, 45% reported an annual household income below the federal poverty threshold, and 43% were unemployed or disabled at the time of survey completion. Like the overall sample, the subset tested for criterion validity was predominantly represented by women (94%) and African Americans (88%), while 42.3% attained a high school education or less, 66.7% reported an annual household income below the federal poverty threshold, and 54.7% were unemployed or disabled.

Table 1. Description of SLE GOAL participants in the SA-BILD validation assessment*
 SA-BILD participants (n = 711)Criterion validity assessment subset (n = 150)
  1. Values are the number (percentage) unless indicated otherwise. SLE = systemic lupus erythematosus; GOAL = Georgians Organized Against Lupus; SA-BILD = self-administered Brief Index of Lupus Damage; SLAQ = Systemic Lupus Activity Questionnaire; SF-12 = Short Form 12; MCS = mental component summary; PCS = physical component summary; RDCI = Rheumatic Diseases Comorbidity Index.

  2. a

    Household income below poverty level was available for 673 of 711 patients.

Sociodemographics  
Age at survey, mean ± SD years45.9 ± 13.442.4 ± 13.1
Sex  
Women666 (93.7)141 (94.0)
Ethnicity  
African American554 (77.9)132 (88.0)
White143 (20.1)17 (11.3)
Other ethnicity14 (2.0)1 (0.7)
Education attainment  
High school or less248 (35.0)63 (42.3)
Some college226 (31.9)55 (36.9)
College or higher234 (33.1)31 (20.8)
Household income below poverty level305 (45.3)a96 (66.7)
Unemployed or disabled306 (43.0)82 (54.7)
Disease status, mean ± SD  
Disease duration, years13.3 ± 9.010.4 ± 9.1
Disease activity, SLAQ score17.2 ± 9.417.7 ± 9.1
Mental health, SF-12 MCS43.8 ± 11.243.3 ± 10.2
Physical health, SF-12 PCS39.3 ± 10.438.2 ± 10.0
Comorbidity index, RDCI2.9 ± 1.92.7 ± 1.9
Health status  
Fair/poor362 (51.0)86 (57.3)
Health care utilization, mean ± SD  
Annual rheumatologist visits3.2 ± 2.93.9 ± 2.7
Annual physician visits9.6 ± 12.18.8 ± 7.7

The mean score for self-reported disease activity was moderately high (>17) in both the SA-BILD participants and individuals assessed for criterion validity. Half of the participants from both groups reported fair or poor health status, with mental and physical component scores below the general population average. In both groups, the average annual visits to the rheumatologist and overall physician visits were ∼3 and ∼10, respectively.

Test–retest reliability was assessed among 32 GOAL respondents who were readministered the SA-BILD questionnaire. The median time between the first and second assessment was 30.8 days (range 14–53 days). All of the patients were women and their average age was 38 years; 56% were African American and 41% were white. The Spearman's test–retest coefficient was 0.93 (P < 0.0001).

Criterion validity was assessed among GOAL respondents for whom the SDI was completed during a regular lupus clinic visit. The mean ± SD time between the SA-BILD and the SDI assessments was 162 ± 75 days. Table 2 shows the percentage agreement between each SDI item and the corresponding SA-BILD item. The observed item-by-item agreement ranged from 81–99%, while the PABAK ranged from 0.73–0.99, except for retinal change or optic atrophy (PABAK = 0.63) and thrombosis (PABAK = 0.67). Table 3 shows that the distributions of the SDI and SA-BILD scores were similar, and the correlation of the overall score between both instruments was moderately high (ρ = 0.59, P < 0.0001).

Table 2. Item-by-item comparison of the SDI and SA-BILD in a subset of 150 SLE GOAL participants*
Organ system and itemSDI, no. (%)SA-BILD, no. (%)SDI versus SA-BILD
Agreement (%)PABAK
  1. SDI = Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index; SA-BILD = self-administered Brief Index of Lupus Damage; SLE = systemic lupus erythematosus; GOAL = Georgians Organized Against Lupus; PABAK = prevalence-adjusted bias-adjusted kappa; ESRD = end-stage renal disease; GFR = glomerular filtration rate; GI = gastrointestinal.

Ocular    
Any cataract ever12 (8.0)20 (13.3)920.84
Retinal change or optic atrophy2 (1.3)27 (18.1)810.63
Neuropsychiatric    
Cerebrovascular accident/resection6 (4.0)13 (8.7)910.81
Cognitive impairment or psychosis7 (4.7)8 (5.3)910.83
Cranial/peripheral neuropathy5 (3.3)Omitted 
Seizures requiring therapy ≥6 months8 (5.3)17 (11.3)940.88
Transverse myelitis2 (1.3)7 (4.7)950.91
Renal    
ESRD (dialysis/transplant)5 (3.3)6 (4.0)980.96
GFR <50 ml/minute/1.73 m26 (4.0)Omitted 
Proteinuria >3.5 gm/24 hours3 (2.0)Omitted 
Pulmonary    
Pleural fibrosis0 (0)Omitted 
Pulmonary fibrosis7 (4.7)8 (5.4)960.92
Pulmonary hypertension4 (2.7)17 (11.4)870.73
Pulmonary infarction or resection0 (0)Omitted 
Shrinking lung0 (0)Omitted 
Cardiovascular    
Angina or coronary artery bypass3 (2.0)4 (2.7)990.97
Cardiomyopathy4 (2.7)Omitted 
Myocardial infarction3 (2.0)11 (7.4)930.87
Pericarditis ≥6 months1 (0.7)13 (8.8)890.77
Valvular disease2 (1.3)Omitted 
Peripheral vascular    
Claudication, ≥6 months0 (0)Omitted 
Minor tissue loss (pulp space)5 (3.3)14 (9.3)900.80
Significant tissue loss, ever0 (0)0 (0)990.99
Venous thrombosis3 (2.0)24 (16.0)830.67
Gastrointestinal    
Chronic peritonitis0 (0)0 (0)980.96
Infarction/abdominal organ resection3 (2.0)8 (5.3)950.91
Mesenteric insufficiency0 (0)Omitted 
Pancreatic insufficiency0 (0)Omitted 
Stricture or upper GI tract surgery1 (0.7)5 (3.3)960.92
Musculoskeletal    
Avascular necrosis4 (2.7)8 (5.3)930.87
Deforming or erosive arthritis10 (6.7)Omitted 
Muscle atrophy or weakness11 (7.3)Omitted 
Osteomyelitis0 (0)1 (0.7)990.99
Osteoporosis with fracture2 (1.3)15 (10.1)910.81
Ruptured tendon0 (0)Omitted 
Skin    
Extensive scarring/panniculitis17 (11.3)Omitted 
Scarring chronic alopecia20 (13.3)Omitted 
Skin ulceration (not thrombosis)3 (2.0)15 (10.1)910.81
Others    
Diabetes mellitus9 (6.0)14 (9.3)930.85
Malignancy4 (2.7)9 (6.0)970.93
Premature gonadal failure (age <40 years)4 (4.7)10 (11.6)920.84
Table 3. SLE damage scores in a subset of 150 GOAL participants*
ScoreScores >0, no. (%)MeanMedian (IQR)Maximum scoreCorrelation
  1. SLE = systemic lupus erythematosus; GOAL = Georgians Organized Against Lupus; IQR = interquartile range; SDI = Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index; SA-BILD = self-administered Brief Index of Lupus Damage.

SDI (n = 150)88 (58.7)1.371 (0–2)7
SA-BILD (n = 150)107 (71.3)2.051 (0–3)100.59 (P < 0.0001)

The distribution of the SA-BILD score in the overall GOAL sample of 711 patients was very similar to the sample used to determine criterion validity, with a median of 2.0 (interquartile range 0–3) and maximum of 18 (data not shown). The acceptability of the SA-BILD questionnaire in the overall GOAL sample was high, with only 3 items having >1% of missing values as a consequence of missing responses. These items were pericarditis (7 missing), chronic peritonitis (9 missing), and premature gonadal failure (7 missing).

Construct validity was assessed by analyzing the association of sociodemographic, disease status, health status, and health care utilization measures across quartiles of SA-BILD scores (Table 4). As expected, higher SA-BILD scores, which represented progressively greater SLE damage, were associated with older age and longer disease duration as well as with progressively worse health scores (higher SLE activity index, lower physical health score, and higher comorbidity index). As SA-BILD scores increased, the proportions of unemployed or disabled individuals and of patients reporting poor or fair health also increased. Similarly, the annual number of physician visits increased progressively as SA-BILD scores increased. We also found lower SA-BILD scores in women and in patients who attained a high school education or less. Ethnicity, poverty, mental health, and annual visits to the rheumatologist were not associated with increasing SA-BILD scores.

Table 4. Comparison of demographics, health status, and health utilization by quartiles of SA-BILD score in SLE patients from the GOAL cohort (n = 711)*
 0 (n = 192)1 (n = 149)2–3 (n = 205)≥4 (n = 165)Pa
  1. Values are the number (percentage) unless indicated otherwise. SA-BILD = self-administered Brief Index of Lupus Damage; SLE = systemic lupus erythematosus; GOAL = Georgians Organized Against Lupus; SLAQ = Systemic Lupus Activity Questionnaire; SF-12 = Short Form 12; PCS = physical component summary; MCS = mental component summary; RDCI = Rheumatic Diseases Comorbidity Index.

  2. a

    Calculated with one-way analysis of variance test for continuous variables and Cochran-Armitage trend test for categorical variables.

Sociodemographics     
Age at survey, mean ± SD years40.6 ± 12.644.7 ± 13.147.6 ± 13.251.2 ± 12.5< 0.001
Women185 (96.4)139 (93.3)193 (94.1)149(90.3)0.036
African American131 (70.1)127 (87.6)167 (82.7)129 (79.1)0.055
High school education or less132 (69.5)103 (69.6)122 (59.5)103 (62.4)0.048
Household income below poverty level75 (41.0)65 (45.1)92 (47.7)73 (47.7)0.17
Unemployed or disabled53 (27.6)59 (39.6)97 (47.3)97 (58.8)< 0.001
SLE disease status     
Disease duration, mean ± SD years10.7 ± 8.212.5 ± 9.013.6 ± 8.716.7 ± 9.3< 0.001
SLAQ score, mean ± SD13.0 ± 8.716.9 ± 9.218.7 ± 9.120.5 ± 8.9< 0.001
General health status     
Fair/poor self-reported health63 (32.8)73 (49.0)114 (55.9)112 (67.9)< 0.001
SF-12 PCS, mean ± SD45.2 ± 10.439.8 ± 9.837.7 ± 9.334.0 ± 8.7< 0.001
SF-12 MCS, mean ± SD44.7 ± 11.143.9 ± 11.843.1 ± 11.443.3 ± 10.80.49
RDCI, mean ± SD1.4 ± 1.32.5 ± 1.63.1 ± 1.64.7 ± 1.7< 0.001
Health care utilization     
Annual rheumatologist visits, mean ± SD2.9 ± 2.73.4 ± 2.73.4 ± 3.23.0 ± 3.10.28
Annual physician visits, mean ± SD7.0 ± 5.98.6 ± 8.39.6 ± 9.313.8 ± 19.8< 0.001

To further examine the relationship between sociodemographic characteristics and damage, we constructed several multivariable models, in which the outcome was the SA-BILD score (either as binary or continuous variables) and the predictors included age, sex, ethnicity, disease duration, education, and employment. All analyses yielded similar conclusions, with age, disease duration, and unemployment emerging as significant predictors of damage.

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. ROLE OF THE STUDY SPONSOR
  9. REFERENCES
  10. Supporting Information

In this study, we validated a self-administered version of the BILD in an independent community-based cohort of SLE patients from the Southeastern US. Questionnaire length and delivery mode have a significant impact on both survey acceptability and response rates ([33]), particularly when the target population includes vulnerable patients, such as the predominantly African American population in this study. We adapted the previously validated interviewer-administered BILD into a written survey that can be mailed to SLE patients, while retaining the psychometric properties and low administrative burden of the original tool. Our findings suggested that the SA-BILD is reliable and acceptable to SLE respondents with diverse sociodemographic backgrounds, and that it has criterion and construct validity comparable to the interviewer-administered BILD.

Like the original BILD, we found very good or good item-by-item agreement between the SA-BILD and SDI. The PABAK surpassed 0.80 for most of the items; the only exceptions were retinal change or optic atrophy (PABAK = 0.63), venous thrombosis (PABAK = 0.67), pulmonary hypertension (PABAK = 0.73), and pericarditis (PABAK = 0.77). Interestingly, all SA-BILD items were overreported by SLE patients, compared with rheumatologist assessment. Such patient overreporting has been found with the LDIQ ([22]), but not with the original BILD ([23]), suggesting that overreporting may be associated with the self-administered method. Without the assistance of a trained interviewer, overreporting may be the result of patient unfamiliarity with the medical terminology used in the questions. Alternatively, physician underreporting can also explain patient–physician disagreement. As pointed out by the developers of the LDIQ, given the lack of universal medical records in the US health system, physicians might not be aware of all the chronic manifestations accrued in individual patients since the disease onset ([22]). We do not believe that a delay between administration of the SA-BILD and SDI impacted item-by-item agreement in relation to the occurrence of new damage manifestations. The average time between the patient and physician assessment was only 5 months, and the SDI was conducted after the SA-BILD in all cases. If new damage manifestations had occurred after the SA-BILD administration, we would expect the SA-BILD items to be underreported in relation to the SDI. However, as discussed above, all discrepancies were based on more frequent patient reports (or physician underreporting).

We should emphasize that, rather than developing a substitute for the SDI, the goal of the BILD instruments is to have a patient-reported measure that would differentiate between greater and lesser degrees of SLE damage, with minimal administrative burden to patients. Consequently, both the BILD and the SA-BILD include only 26 of the 56 items originally developed for the SDI. When we examined the correlation between the overall SA-BILD and SDI scores, we found a moderately high Spearman's rho correlation (ρ = 0.59, P < 0.0001), which is consistent with findings previously reported with the original BILD (ρ = 0.64). We did not aim to compare the performances of the SA-BILD and the LDIQ, which is the 56-item patient version of the SDI ([22]). However, it is noteworthy that, despite the larger minority representation in our community-based cohort than in the academic-based sample used to validate the LDIQ, the overall correlation with the SDI seemed to be somewhat better for the SA-BILD (ρ = 0.59) than for the LDIQ (ρ = 0.48).

Data from over 700 SLE patients from the GOAL cohort also showed significant associations in the expected directions between SA-BILD scores and age, disease duration, and socioeconomic and health status, as well as with disease outcomes and health service utilization measures. Consistent with prior studies using the SDI, SLAQ, or original BILD, increasing SA-BILD scores were positively associated with poorer scores of self-reported physical health, greater disease activity, greater comorbidity index, and higher annual average of visits to physicians ([16, 23, 28, 34-36]). Similarly, higher SA-BILD scores were associated with higher rates of unemployment or disability and poor or fair overall health ([21]). Therefore, our findings suggested that the SA-BILD may have a role in predicting long-term outcomes, although such longitudinal studies have yet to be completed. However, it was unexpected that the number of annual visits to the rheumatologist did not increase along with higher SA-BILD scores, as had occurred with participants of the LOS cohort. Given that there was a larger proportion of unemployed participants among GOAL participants with more severe damage, it is plausible that these patients may face barriers to specialized health care access and may be monitored in the primary care setting.

A number of caveats need to be noted regarding the present study. First, the SA-BILD is not a substitute for the physician's assessment of organ damage in the clinical setting; the gold standard instrument to assess organ damage for SLE outcomes research remains the physician-reported SDI, when it is feasible. Second, the SA-BILD questionnaire is only available in English, and further efforts are warranted to translate and validate the instrument for use among non–English-speaking SLE patients. Finally, because our study was cross-sectional, we did not have insight on the value of the instrument for longitudinal studies. To establish the sensitivity to change, prospective cohort studies correlating physician and patient assessments are necessary.

The 2 strengths of our study were the population-based nature and diverse sociodemographic characteristics of the targeted sample, which provided external legitimacy to this instrument as a self-administered measure of patient-reported damage for epidemiologic research in SLE. The survey respondents were predominantly African American and also represented socioeconomically disadvantaged subgroups that are most affected by SLE. Not surprisingly, SLE patients from minority groups accrue higher organ damage at younger ages than white patients or those from more privileged social classes ([9, 37, 38]). However, minority groups are generally underrepresented in outcome measure development and validation studies ([17, 22, 23, 39]). The SA-BILD promises to be an economic alternative to capture organ damage for epidemiologic studies in US communities with a large representation of high-risk subjects.

Second, rather than developing a new instrument, this collaborative effort took advantage of adapting an existing short instrument validated among SLE patients with a different sociodemographic profile. Despite the distinctive ethnic and socioeconomic characteristics of the GOAL cohort, and the modifications needed to tailor the BILD to a written version, the SA-BILD showed moderately high criterion and construct validity performances comparable with the original interviewer-administered version ([23]).

In conclusion, the SA-BILD was acceptable to SLE patients from a predominantly African American population who responded to a self-administered annual survey. The reliability and criterion and construct validity coefficients of the SA-BILD were within the range of previously validated patient-reported tools. Therefore, the SA-BILD may be a practical and cost-effective option for collecting patient-reported damage for epidemiologic SLE research when vulnerable SLE populations are targeted and physician assessment is not feasible. Further research is warranted, including longitudinal studies to assess sensitivity to change. Translation to other languages would also be desirable to determine the potential value of this instrument among other high-risk minorities with SLE.

AUTHOR CONTRIBUTIONS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. ROLE OF THE STUDY SPONSOR
  9. REFERENCES
  10. Supporting Information

All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published. Dr. Drenkard had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study conception and design. Drenkard, Yazdany, Trupin, Dunlop-Thomas, Bao, Lim.

Acquisition of data. Drenkard, Dunlop-Thomas, Bao, Lim.

Analysis and interpretation of data. Drenkard, Trupin, Katz, Bao.

ROLE OF THE STUDY SPONSOR

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. ROLE OF THE STUDY SPONSOR
  9. REFERENCES
  10. Supporting Information

Human Genome Science Inc. and GlaxoSmithKline had no role in the study design or in the collection, analysis, or interpretation of the data, the writing of the manuscript, or the decision to submit the manuscript for publication. Publication of this article was not contingent upon approval by Human Genome Science Inc. and GlaxoSmithKline.

REFERENCES

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  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. ROLE OF THE STUDY SPONSOR
  9. REFERENCES
  10. Supporting Information
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Supporting Information

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. AUTHOR CONTRIBUTIONS
  8. ROLE OF THE STUDY SPONSOR
  9. REFERENCES
  10. Supporting Information

Additional Supporting Information may be found in the online version of this article.

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ACR_22231_sm_SupplApp1.doc100KSupplementary Appendix

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