Somatosensation in OA: exploring the relationships of pain sensitization, vibratory perception and spontaneous pain

Background

Pain in osteoarthritis (OA) remains poorly understood. Different types of somatosensory alterations exist in OA including hyperesthesia and increased sensitivity to painful stimuli as well as those of decreased sensitivity to cutaneous stimuli including vibratory perception threshold. The relationship between these different somatosensory measures has not been previously evaluated in OA. In this observational study, we evaluated relationships between vibratory perception (VPT), pressure pain detection thresholds (PPT), allodynia and subjective pain in knee OA.

Methods

Forty-two persons with moderate to severe knee OA and 12 controls without OA were evaluated. VPT was measured using a biothesiometer. Allodynia was measured by application of a 60 g Von Frey monofilament repeatedly to predetermined sites. PPTs were measured using a pressure algometer.

Results

Increased vibratory acuity was associated with lower PPTs and presence of allodynia. Allodynia was more common in OA than controls (54.8% vs 16.6%, p = 0.024 in the ipsilateral knee, and 42.9% vs 0%, p = 0.005 in the contralateral knee). OA participants with allodynia had lower PPTs than those without allodynia. In those with OA, spontaneous knee pain was associated with lower PPTs and with allodynia.

Conclusion

This study confirms the presence of somatosensory alterations in OA. Sensory alterations (vibratory perception) were shown to be related to nociceptive alterations (sensitization) in OA, showing a general increased sensitivity to cutaneous mechanical stimulation. Understanding these relationships is an important step in delineating the complicated pathophysiology of pain processing in OA.

Caregiving, dyadic quality of life and dyadic relationships in lupus

Aims

Systemic lupus erythematosus (SLE) mostly affects young women, adversely affecting their quality of life (QOL). Caregivers may experience caregiver burden (CGB), and it may lower the quality of their relationship. Herein we studied caregiving and CGB and their effects on QOL and relationships in SLE.

Methods

We recruited 10 dyads from the Lupus Clinic. Data collected included demographics, CGB (CGB Scale, screen for CGB), QOL (SF-36) and the quality of the dyadic relationship (Dyadic Adjustment Scale (DAS)). We calculated correlation coefficients for associations between (i) CGB and (ii) dyadic QOL or DAS.

Results

The mean (± SD) age of SLE patients was 35.2 (± 9) years and of caregivers was 37.3 (± 9.64) years. The mean (± SD, min–max) total CGB score was 9.1 (± 5.8, 0–19). The caregiver's QOL correlated strongly with some of the domains of the patient's QOL. The SLE-related CGB was associated with the caregiver's own QOL and their SLE partner's QOL. The dyadic DAS was linked to the patient's QOL.

Conclusions

Because (i) CGB in SLE is associated with the caregiver's own QOL and with their SLE partner's QOL, and because (ii) the dyadic DAS score is linked primarily to the patient's QOL, then to optimize patient health outcomes and to decrease CGB, focus should be not only on the patient but should include the dyadic unit. Significant findings: To optimize patient outcomes of SLE patients, focus should be on the dyadic unit. CGB in SLE is associated with the caregiver's own QOL and with the SLE partner's QOL, making it crucial to study this relationship in more detail.

Serum free light chains, interferon-alpha, and interleukins in systemic lupus erythematosus

OBJECTIVE

Interleukin-6 (IL-6), interleukin-10 (IL-10), interferon-alpha (IFN-α), and free light chains (FLCs: lambda, kappa) have all been noted to be of importance in systemic lupus erythematosus (SLE). Herein, we quantified and explored the relationship between these inflammatory mediators and disease activity in SLE; and stratified by their current anti-dsDNA antibody status.

METHODS

Seventy-seven SLE patients underwent assessment of disease activity using the SLE disease activity index (SLEDAI). Serum FLC (lambda, kappa, and total), IL-6, IL-10, and IFN-α were quantified. Demographics of disease characteristics were determined by chart reviews. Statistical analyses included Mann-Whitney test, chi square, and linear regression analyses.

RESULTS

Mean (SD) age of the patients was 44.9 ± 12.7 years; SLEDAI (mean ± SD) was 3.4 ± 4.0. Serum lambda FLC levels had a moderate correlation (r = 0.46 with physician global assessment, 0.44 with SLEDAI) and the strongest correlation with disease activity as compared with other inflammatory mediators including current dsDNA antibody status. After adjusting for prednisone use, the correlation of lambda FLC with PGA (r = 0.48) and SLEDAI (r = 0.52) was better than of current dsDNA antibody status with PGA (r = 0.33) and adjusted SLEDAI (r = 0.24), respectively. IL-10 and IFN-α activity did not correlate with disease activity. Serum FLC and IL-6 levels could differentiate between active and inactive SLE patients. Serum lambda FLC and IL-6 levels differed significantly among patients with and without current dsDNA antibodies. Serum lambda FLC levels accounted for 31% of variance in SLEDAI scores.

CONCLUSION

Serum FLC and IL-6 are potentially useful biomarkers of disease activity in SLE. Further studies, with larger study sample and longitudinal design, are indicated.

Validation of the Cutaneous Lupus Disease Area and Severity Index (CLASI) using physician- and patient-assessed health outcome measures

BACKGROUND

The Cutaneous Lupus Disease Area and Severity Index (CLASI) has not been validated using rheumatologist-conducted disease activity and damage assessments, especially cutaneous assessments. Active skin disease and skin damage may have substantial effects on patient-reported outcomes and on body image.

OBJECTIVE

We sought to validate the CLASI against: (1) physician-assessed disease activity and damage measures; and (2) patient-reported assessment of quality of life and body image.

METHODS

Cross-sectional data were collected from 31 patients with cutaneous lupus erythematosus. Cutaneous disease activity and damage were measured by using the CLASI. Disease activity (using the Safety of Estrogens in Lupus Erythematosus National Assessment-Systemic Lupus Erythematosus [SLE] Disease Activity Index [SLEDAI}), damage (Systemic Lupus International Collaboration Clinics-American College of Rheumatology Damage Index [SDI]), quality of life (LupusPRO), and body image (Body Image Quality of Life Inventory) were obtained. Descriptive statistics and Spearman correlations were ascertained.

RESULTS

Mean (SD) age was 42.3 (12.8) years; 97% were women. The mean (SD) CLASI activity and damage scores were 10.5 (7.4) and 9.9 (9.5). Correlations noted were: total CLASI activity and SLEDAI-rash (r = 0.42, P = .02), CLASI-mucosal and SLEDAI-mucosal (r = 0.65, P = .001), CLASI-recent hair loss and SLEDAI-alopecia (r = 0.61, P = .001), and total CLASI activity and LupusPRO symptoms domain (r = -0.38, P = .04). Total CLASI-damage correlated with SDI-scarring/alopecia (r = 0.51, P = .004), SDI-extensive scarring/panniculum (r = 0.55, P = .003), and SDI-skin ulceration (r = 0.36, P = .05). CLASI scalp scarring correlated with SDI-skin scarring/alopecia (r = 0.94, P = .001). CLASI activity on the face and nose was associated with significant concerns on the Body Image Quality of Life Inventory.

LIMITATIONS

Limitations include small sample size.

CONCLUSION

CLASI activity and damage scores correlate with physician-assessed cutaneous activity and damage in cutaneous lupus erythematosus in patients with SLE. Cutaneous activity in visible areas may generate body image concerns.

Rheumatologists' quality of care for lupus: comparison study between a university and county hospital

OBJECTIVE

Quality of care received from physicians may impact health outcomes in systemic lupus erythematosus (SLE). We compared physician quality of care (P-QOC), health-related quality of life (HRQOL), and disease activity and damage between SLE patients receiving outpatient care at a university and a county rheumatology clinic.

METHODS

Forty-two university and 41 county clinic SLE patients provided data on 5 P-QOC parameters and HRQOL health outcomes (Short Form 36 [SF-36] health survey and EuroQol 5-domain instrument [EQ-5D]). Disease activity and damage were measured. Chi-square analysis and Student's t-tests were used for comparisons.

RESULTS

Overall satisfaction with medical care was similar; however, university patients had higher P-QOC scores than county patients in "perception of doctor's understanding of impact of SLE on patient's life" (P = 0.02) and "providing education/educational information to understand their disease" (P = 0.05). HRQOL, disease activity, and damage were similar in the 2 groups. Overall satisfaction with medical care was directly related SF-36 general health (r = 0.34, P = 0.03) and EQ-5D visual analog scale on state of health (r = 0.39, P = 0.01), and inversely related EQ-5D pain (r = -0.37, P = 0.02).

CONCLUSION

Patient perceptions of P-QOC differed across the 2 centers despite similar demographics, clinical and HRQOL outcomes, and significant overlap in the physicians serving each clinic. Patients' overall satisfaction with medical care is associated with better HRQOL.

A brief assessment tool for body image in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) may adversely affect body image in multitude ways. Development and validation of a brief and valid SLE specific body image tool were undertaken. Eleven items were identified on interview of 21 SLE patients for the Body Image Lupus Scale (BILS v1.0). The tool was administered to 70 SLE patients. Based on analysis, feedback, and refinement of items, the final iteration BILS v1.2 with five items was administered to 233 SLE patients along with validated body image measures (Situational Inventory of Body Image Dysphoria and Body Image Quality of Life Inventory) and health-related quality of life measures for a subsample. The BILS scores' had an internal consistency reliability of .94. It correlated with both the referent body image measures, and with health-related quality of life. It differentiated participants by health status and disease activity. Test-retest reliability estimates exceeded .90. These results support the psychometric properties of BILS.

Asymmetric loading and bone mineral density at the asymptomatic knees of patients with unilateral hip osteoarthritis

OBJECTIVE

In patients with unilateral end-stage hip osteoarthritis (OA), the contralateral knee is known to be at greater risk for end-stage knee OA compared to the ipsilateral (i.e., same-side) knee. The contralateral knee is known to have increased dynamic joint loads compared to the ipsilateral knee. The present study was undertaken to examine patients who had unilateral hip OA but who did not have symptoms of knee OA, in order to detect early asymmetries in knee loading.

METHODS

Data on 62 patients with unilateral hip OA were evaluated. Patients underwent gait analyses of dynamic knee loads as well as dual x-ray absorptiometry for determination of bone mineral density (BMD) in both knees. Differences between knees were compared.

RESULTS

Peak dynamic knee loads were significantly higher at the contralateral knee compared to the ipsilateral knee (mean ± SD 2.46 ± 0.71 percent of body weight × height versus 2.23 ± 0.81 percent of body weight × height; P = 0.029). Similarly, medial compartment tibial BMD was significantly higher in the contralateral knee compared to the ipsilateral knee (mean ± SD 0.897 ± 0.208 gm/cm(2) versus 0.854 ± 0.206 gm/cm(2); P = 0.033). Interestingly, there was a direct correlation between the contralateral:ipsilateral dynamic knee load and contralateral:ipsilateral medial compartment tibial BMD (ρ = 0.287, P = 0.036).

CONCLUSION

The risk of developing progressive symptomatic OA in contralateral knees is higher compared to the risk in ipsilateral knees in patients with unilateral hip OA. The present study demonstrates that loading and structural asymmetries appear early in the disease course, while the knees are still asymptomatic. These early biomechanical asymmetries may have corresponding long-term consequences, providing further evidence for the potential role of loading in OA onset and progression.

The autoimmune disease risk allele of UBE2L3 in African American patients with systemic lupus erythematosus: a recessive effect upon subphenotypes

OBJECTIVE

UBE2L3 is associated with susceptibility to systemic lupus erythematosus (SLE) and rheumatoid arthritis in European ancestry populations, and this locus has not been investigated fully in non-European populations. We studied the UBE2L3 risk allele for association with SLE, interferon-α (IFN-α), and autoantibodies in a predominantly African American SLE cohort.

METHODS

We studied 395 patients with SLE and 344 controls. The UBE2L3 rs5754217 polymorphism was genotyped using Taqman primer-probe sets, and IFN-α was measured using a reporter cell assay.

RESULTS

The UBE2L3 rs5754217 T allele was strongly enriched in African American patients with anti-La antibodies as compared to controls, and a recessive model was the best fit for this association (OR 2.55, p = 0.0061). Serum IFN-α also demonstrated a recessive association with the rs5754217 genotype in African American patients, and the TT/anti-La-positive patients formed a significantly high IFN-α subgroup (p = 0.0040). Similar nonstatistically significant patterns of association were observed in the European American patients with SLE. Case-control analysis did not show large allele frequency differences, supporting the idea that this allele is most strongly associated with anti-La-positive patients.

CONCLUSION

This pattern of recessive influence within a subgroup of patients may explain why this allele does not produce a strong signal in standard case-control studies, and subphenotypes should be included in future studies of UBE2L3. The interaction we observed between UBE2L3 genotype and autoantibodies upon serum IFN-α suggests a biological role for this locus in patients with SLE in vivo.

Serum free light chains as biomarkers for systemic lupus erythematosus disease activity

OBJECTIVE

To evaluate serum free light chains (FLC) as a putative biomarker of systemic lupus erythematosus (SLE) activity.

METHODS

Seventy-five SLE patients and 41 age- and sex-matched rheumatoid arthritis (RA) controls were enrolled. Disease activity was assessed using the Safety of Estrogens in Lupus Erythematosus: National Assessment version of the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) definition and physician global assessments for SLE and the Disease Activity Score in 28 joints for RA. Serum FLC levels were compared against other biomarkers (IgG, C3, C4, double-stranded DNA [dsDNA] antibody). Nonparametric tests were used to compare 1) FLC and IgG in SLE versus RA and healthy controls, 2) FLC and IgG among different levels of activity in SLE, and 3) FLC in active versus nonactive RA. Correlation of FLC, C3, C4, dsDNA antibody, and IgG with the SLEDAI and modified SLEDAI (M-SLEDAI) were obtained.

RESULTS

FLC was higher in SLE than in RA; both were higher than referent healthy controls. Total FLC was significantly higher in subjects with greater SLE disease activity than lower/no activity. There were no significant differences in IgG, C4, or dsDNA antibody stratified by disease activity. Total FLC and C3 showed moderate to strong correlation with the SLEDAI and M-SLEDAI. In RA, no differences were seen in FLC levels for different levels of disease activity. Similar results were seen after controlling for renal function, age, and sex. In multiple linear regression, FLC significantly explained 50% variance of the SLEDAI after adjusting for renal function, age, and sex.

CONCLUSION

Serum FLC levels correlate strongly with disease activity in SLE, but not in RA. Serum FLC may be used as a biomarker of SLE disease activity.

Autoimmune disease risk variant of IFIH1 is associated with increased sensitivity to IFN-α and serologic autoimmunity in lupus patients

Increased IFN-α signaling is a heritable risk factor for systemic lupus erythematosus (SLE). IFN induced with helicase C domain 1 (IFIH1) is a cytoplasmic dsRNA sensor that activates IFN-α pathway signaling. We studied the impact of the autoimmune-disease-associated IFIH1 rs1990760 (A946T) single nucleotide polymorphism upon IFN-α signaling in SLE patients in vivo. We studied 563 SLE patients (278 African-American, 179 European-American, and 106 Hispanic-American). Logistic regression models were used to detect genetic associations with autoantibody traits, and multiple linear regression was used to analyze IFN-α-induced gene expression in PBMCs in the context of serum IFN-α in the same blood sample. We found that the rs1990760 T allele was associated with anti-dsDNA Abs across all of the studied ancestral backgrounds (meta-analysis odds ratio = 1.34, p = 0.026). This allele also was associated with lower serum IFN-α levels in subjects who had anti-dsDNA Abs (p = 0.0026). When we studied simultaneous serum and PBMC samples from SLE patients, we found that the IFIH1 rs1990760 T allele was associated with increased IFN-induced gene expression in PBMCs in response to a given amount of serum IFN-α in anti-dsDNA-positive patients. This effect was independent of the STAT4 genotype, which modulates sensitivity to IFN-α in a similar way. Thus, the IFIH1 rs1990760 T allele was associated with dsDNA Abs, and in patients with anti-dsDNA Abs this risk allele increased sensitivity to IFN-α signaling. These studies suggest a role for the IFIH1 risk allele in SLE in vivo.

Network analysis of associations between serum interferon-α activity, autoantibodies, and clinical features in systemic lupus erythematosus

OBJECTIVE

Interferon-α (IFNα) is a primary pathogenic factor in systemic lupus erythematosus (SLE), and high IFNα levels may be associated with particular clinical manifestations. The prevalence of individual clinical and serologic features differs significantly by ancestry. This study was undertaken to detect associations between clinical and serologic disease manifestations and serum IFNα activity in a large diverse SLE cohort, using multivariate and network analyses.

METHODS

We studied 1,089 SLE patients (387 African American, 186 Hispanic American, and 516 European American patients). The presence or absence of individual American College of Rheumatology (ACR) clinical criteria for SLE, autoantibodies, and serum IFNα activity data were analyzed in univariate and multivariate models. Iterative multivariate logistic regression was performed in each ancestral background group separately to establish the network of associations between variables that were independently significant following Bonferroni correction.

RESULTS

In all ancestral backgrounds, high IFNα activity was associated with anti-Ro and anti-double-stranded DNA antibodies (P = 4.6 × 10(-18) and P = 2.9 × 10(-16) , respectively). Younger age, non-European ancestry, and anti-RNP were also independently associated with increased serum IFNα activity (P ≤ 6.7 × 10(-4) ). We found 14 unique associations between variables in network analysis, and only 7 of these associations were shared among >1 ancestral background. Associations between clinical criteria were different for different ancestral backgrounds, while autoantibody-IFNα relationships were similar across backgrounds. IFNα activity and autoantibodies were not associated with ACR clinical features in multivariate models.

CONCLUSION

Our findings indicate that serum IFNα activity is strongly and consistently associated with autoantibodies, and not independently associated with clinical features in SLE. IFNα may be more relevant to humoral tolerance and initial pathogenesis than later clinical disease manifestations.

Trait-stratified genome-wide association study identifies novel and diverse genetic associations with serologic and cytokine phenotypes in systemic lupus erythematosus

Introduction

Systemic lupus erythematosus (SLE) is a highly heterogeneous disorder, characterized by differences in autoantibody profile, serum cytokines, and clinical manifestations. SLE-associated autoantibodies and high serum interferon alpha (IFN-α) are important heritable phenotypes in SLE which are correlated with each other, and play a role in disease pathogenesis. These two heritable risk factors are shared between ancestral backgrounds. The aim of the study was to detect genetic factors associated with autoantibody profiles and serum IFN-α in SLE.

Methods

We undertook a case-case genome-wide association study of SLE patients stratified by ancestry and extremes of phenotype in serology and serum IFN-α. Single nucleotide polymorphisms (SNPs) in seven loci were selected for follow-up in a large independent cohort of 538 SLE patients and 522 controls using a multi-step screening approach based on novel metrics and expert database review. The seven loci were: leucine-rich repeat containing 20 (LRRC20); protein phosphatase 1 H (PPM1H); lysophosphatidic acid receptor 1 (LPAR1); ankyrin repeat and sterile alpha motif domain 1A (ANKS1A); protein tyrosine phosphatase, receptor type M (PTPRM); ephrin A5 (EFNA5); and V-set and immunoglobulin domain containing 2 (VSIG2).

Results

SNPs in the LRRC20, PPM1H, LPAR1, ANKS1A, and VSIG2 loci each demonstrated strong association with a particular serologic profile (all odds ratios > 2.2 and P < 3.5 × 10^-4). Each of these serologic profiles was associated with increased serum IFN-α. SNPs in both PTPRM and LRRC20 were associated with increased serum IFN-α independent of serologic profile (P = 2.2 × 10^-6 and P = 2.6 × 10^-3 respectively). None of the SNPs were strongly associated with SLE in case-control analysis, suggesting that the major impact of these variants will be upon subphenotypes in SLE.

Conclusions

This study demonstrates the power of using serologic and cytokine subphenotypes to elucidate genetic factors involved in complex autoimmune disease. The distinct associations observed emphasize the heterogeneity of molecular pathogenesis in SLE, and the need for stratification by subphenotypes in genetic studies. We hypothesize that these genetic variants play a role in disease manifestations and severity in SLE.

Genetic variation at the IRF7/PHRF1 locus is associated with autoantibody profile and serum interferon-alpha activity in lupus patients

OBJECTIVE

Interferon-alpha (IFNalpha) is a heritable risk factor for systemic lupus erythematosus (SLE). Genetic variation near IRF7 is implicated in SLE susceptibility. SLE-associated autoantibodies can stimulate IFNalpha production through the Toll-like receptor/IRF7 pathway. This study was undertaken to determine whether variants of IRF7 act as risk factors for SLE by increasing IFNalpha production and whether autoantibodies are important to this phenomenon.

METHODS

We studied 492 patients with SLE (236 African American, 162 European American, and 94 Hispanic American subjects). Serum levels of IFNalpha were measured using a reporter cell assay, and single-nucleotide polymorphisms (SNPs) in the IRF7/PHRF1 locus were genotyped.

RESULTS

In a joint analysis of European American and Hispanic American subjects, the rs702966 C allele was associated with the presence of anti-double-stranded DNA (anti-dsDNA) antibodies (odds ratio [OR] 1.83, P = 0.0069). The rs702966 CC genotype was only associated with higher serum levels of IFNalpha in European American and Hispanic American patients with anti-dsDNA antibodies (joint analysis P = 4.1 x 10(-5) in anti-dsDNA-positive patients and P = 0.99 in anti-dsDNA-negative patients). In African American subjects, anti-Sm antibodies were associated with the rs4963128 SNP near IRF7 (OR 1.95, P = 0.0017). The rs4963128 CT and TT genotypes were associated with higher serum levels of IFNalpha only in African American patients with anti-Sm antibodies (P = 0.0012). In African American patients lacking anti-Sm antibodies, an effect of anti-dsDNA-rs702966 C allele interaction on serum levels of IFNalpha was observed, similar to the other patient groups (overall joint analysis P = 1.0 x 10(-6)). In European American and Hispanic American patients, the IRF5 SLE risk haplotype showed an additive effect with the rs702966 C allele on IFNalpha level in anti-dsDNA-positive patients.

CONCLUSION

Our findings indicate that IRF7/PHRF1 variants in combination with SLE-associated autoantibodies result in higher serum levels of IFNalpha, providing a biologic relevance for this locus at the protein level in human SLE in vivo.

Lupus-specific health outcome measure for US patients: the LupusQoL-US version

Background:

Patient-reported outcomes are valuable for the management of chronic diseases like systematic lupus erythematosus (SLE), but no measures have been validated for use in US-based patients with SLE.

Objectives:

To adapt and assess the validity and reliability of an SLE-specific quality of life (QoL) measure developed in the United Kingdom, the LupusQoL, for use in US-based patients with SLE.

Methods:

Debriefing interviews of subjects with SLE guided the language modifications of the tool. The LupusQoL-US, SF-36 and EQ5D were administered. Internal consistency (ICR) and test–retest (TRT) reliability, convergent and discriminative validity were examined. Factor analyses were performed.

Results:

The mean (SD) age of the 185 subjects with SLE was 42.5 (12.9) years. ICR and TRT of the eight domains ranged from 0.85 to 0.94 and 0.68 to 0.92, respectively. Related domains on the SF-36 correlated with the LupusQoL domains (physical health and physical function r = 0.73, physical health and role physical r = 0.57, emotional health and mental health r = 0.72, emotional health and role emotional r = 0.48, pain and bodily pain r = 0.66, fatigue and vitality r = 0.70, planning and social functioning r = 0.58). Most LupusQoL-US domains could discriminate between subjects with varied disease activity and damage. Principal component analysis disclosed five factors in the US version, with physical function, pain and planning items loading on one factor.

Conclusions:

These data provide evidence to support the psychometric properties of the LupusQoL-US, suggesting its utility as an assessment tool for patients with SLE in the USA.