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Millicent Stone

Publications and source records attributed to Millicent Stone.

11 recordsLinked to original sources
PubMed2006

LRTae: improving statistical power for genetic association with case/control data when phenotype and/or genotype misclassification errors are present.

BACKGROUND: In the field of statistical genetics, phenotype and genotype misclassification errors can substantially reduce power to detect association with genetic case/control studies. Misclassification also can bias population frequency parameters such as genotype, haplotype, or multi-locus genotype frequencies. These problems are of particular concern in case/control designs because, short of repeated sampling, there is no way to detect misclassification errors. We developed a double-sampling procedure for case/control genetic association using a likelihood ratio test framework. Different approaches have been proposed to deal with misclassification errors. We have chosen the likelihood framework because of the ease with which misclassification probabilities may be incorporated into in the statistical framework and hypothesis testing. The statistic is called the Likelihood Ratio Test allowing for errors (LRTae) and is freely available via software download. RESULTS: We applied our procedure to 10,000 replicates of simulated case/control data in which we introduced phenotype misclassification errors. The phenotype considered is Ankylosing Spondylitis (AS). The LRTae method power was always greater than LRTstd power for the significance levels considered (5%, 1%, 0.1%, 0.01%). Power gains for the LRTae method over the LRTstd method increased as the significance level became more stringent. Multi-locus genotype frequency estimates using LRTae method were more accurate than estimates using LRTstd method. CONCLUSION: The LRTae method can be applied to single-locus genotypes, multi-locus genotypes, or multi-locus haplotypes in a case/control framework and can be more powerful to detect association in case/control studies when both genotype and/or phenotype errors are present. Furthermore, the LRTae method provides asymptotically unbiased estimates of case and control genotype frequencies, as well as estimates of phenotype and/or genotype misclassification rates.

Case-Control Studies↗
PubMed2005

Spondyloarthritis research Consortium of Canada magnetic resonance imaging index for assessment of sacroiliac joint inflammation in ankylosing spondylitis.

OBJECTIVE: To develop a feasible magnetic resonance imaging (MRI)-based scoring system for sacroiliac joint inflammation in patients with ankylosing spondylitis (AS) that requires minimal scan time, does not require contrast enhancement, evaluates lesions separately at each articular surface, and limits the number of sacroiliac images that are scored. METHODS: A scoring method based on the assessment of increased signal denoting bone marrow edema on T2-weighted STIR sequences was used. MRI films were assessed blindly in random order at 2 sites by multiple readers. Intra- and interreader reliability was assessed by intraclass correlation coefficient (ICC); the 24-week response of patients with AS randomized to placebo:infliximab (3:8) was assessed by effect size and standardized response mean. The reliability and responsiveness of the scoring method were compared for STIR and gadolinium diethylenetriaminepentaacetic (Gd-DTPA)-enhanced MRI sequences. RESULTS: We scanned 11 patients with AS with clinically active disease and 11 additional patients randomized to the trial of infliximab therapy. ICC for total sacroiliac joint STIR score ranged from 0.90 to 0.98 (P < 0.00001) and interobserver ICC for combined readers from the 2 sites was 0.84 (P < 0.0001). ICC for change scores was lower for STIR (ICC 0.53) than for Gd-DTPA-enhanced sequences (ICC 0.79). Responsiveness was poor, although fusion was evident in one-third of patients who received treatment (placebo:infliximab) and inflammation scores were low. CONCLUSION: The Spondyloarthritis Research Consortium of Canada MRI index is a feasible and reproducible index for measuring sacroiliac joint inflammation in patients with AS.

Adult↗
PubMed2005

Spondyloarthritis Research Consortium of Canada magnetic resonance imaging index for assessment of spinal inflammation in ankylosing spondylitis.

OBJECTIVE: To develop a feasible magnetic resonance imaging (MRI)-based scoring system for spinal inflammation in patients with spondylarthropathy that requires minimal scan time, does not require contrast enhancement, evaluates the extent of lesions in 3 dimensional planes, and limits the number of vertebral levels that are scored because MRI demonstrates characteristic inflammatory lesions in the spine of patients with ankylosing spondylitis (AS) prior to the development of typical features on plain radiographic. METHODS: Our scoring method was based entirely on the assessment of increased signal denoting bone marrow edema on T2-weighted STIR sequences. Blinded MRI films were assessed in random order at 2 sites by 3 blinded readers at each of the 2 sites (the Universities of Alberta and Toronto). Intra- and interreader reliability was assessed by intraclass correlation coefficient. The 24-week response of patients with AS randomized to infliximab:placebo (8:3) was assessed by effect size and standardized response mean. RESULTS: An initial analysis of all discovertebral units (DVUs) in the spine of 11 patients demonstrated a mean of 3.2 (95% confidence interval 3.2, 5.2) affected units, while limiting the scoring to a maximum of 6 units captured most of the affected units. We scanned 11 patients with AS with clinically active disease and 20 additional patients randomized to a 24-week trial of either infliximab or placebo. Intraobserver reproducibility for the 6-DVU STIR score ranged from 0.93 to 0.98 (P < 0.0001). Interobserver reproducibility of scores by readers from both sites was 0.79 (P < 0.0001) for status score and 0.82 (P < 0.0001) for change score. Analysis of pretreatment and posttreatment scores for all 20 patients randomized to infliximab/placebo showed a large degree of responsiveness (standardized response mean = 0.87). Reproducibility and responsiveness were only slightly improved by using contrast enhancement with gadolinium diethylenetriaminepentaacetic acid. CONCLUSION: The Spondyloarthritis Research Consortium of Canada MRI index is a feasible, reproducible, and responsive index for measuring spinal inflammation in AS.

Adult↗
PubMed2005

Juvenile-onset ankylosing spondylitis is associated with worse functional outcomes than adult-onset ankylosing spondylitis.

OBJECTIVE: To compare functional outcome of patients with juvenile-onset ankylosing spondylitis (JoAS; defined as AS with symptom onset before 16 years of age) with that of patients with adult-onset AS (AoAS) and to identify variables associated with a poor functional outcome of JoAS. METHODS: A cross-sectional study was performed of 326 JoAS patients who participated in a postal survey conducted by the Spondylitis Association of America. This cohort was compared with 2,021 AoAS patients who participated in the same survey. Simple and multiple logistic regression analyses were performed to identify differences with respect to clinical features, demographic features, and functional outcome (defined by the Bath Ankylosing Spondylitis Functional Index [BASFI]) between the 2 groups. A validation cohort of 255 AS patients was also surveyed. RESULTS: The mean +/- SD BASFI score (controlled for disease duration) for JoAS was 51.3 +/- 1.5 compared with 46.4 +/- 0.6 for AoAS (P < 0.0001). Multiple logistic regression identified only age (P < 0.0001) and income status (P < 0.0001) as factors associated with functional impairment. CONCLUSION: It appears that JoAS is a progressive disease and is associated with significant delay in diagnosis and worse functional outcome compared with AoAS. Furthermore, women do worse than men with JoAS. This would argue for the importance of early diagnosis and treatment of AS, particularly in the subgroup of patients with JoAS.

Adolescent↗
PubMed2005

Cartilage biomarkers in ankylosing spondylitis: relationship to clinical variables and treatment response.

OBJECTIVE: Ankylosing spondylitis (AS) is a progressive disease in which chronic inflammation can lead to extensive new bone formation throughout the spine. At present, few measures of the activity or extent of the disease are available. In this study, we sought to determine whether markers of cartilage synthesis and degradation could provide such quantitative measures. METHODS: Serum samples from 23 patients receiving infliximab treatment for AS were obtained at baseline and at weeks 2, 6, 14, and 22. Patients were stratified with respect to joint involvement and baseline levels of inflammatory markers, and responders were defined according to the Assessments in Ankylosing Spondylitis 20% criteria. Serial measurements of interferon-gamma, tumor necrosis factor alpha, transforming growth factor beta (TGFbeta), interleukin-10 (IL-10), and IL-1 were done at each time point. The following biomarkers were measured by enzyme-linked immunosorbent assay: the proteoglycan aggrecan 846 epitope, a marker of cartilage turnover; C-propeptide of type II collagen (CPII), a biosynthesis marker; and the Col2-3/4(long mono) (C2C) and Col2-3/4(short) (C1-2C) neoepitopes, reflecting collagen cleavage of type II collagen and type I/type II collagen, respectively. RESULTS: At baseline, patients with AS demonstrated significant elevations in serum levels of CPII, the 846 epitope, and the CPII-to-C2C (CPII:C2C) ratio (but not C2C or C1-2C) compared with normal controls. Of the biomarkers examined, only CPII:C2C showed a correlation with the C-reactive protein (CRP) level. Among the biomarker-cytokine relationships, TGFbeta demonstrated a trend toward a positive correlation with the 846 epitope. CONCLUSION: In AS, elevated serum levels of CPII and the 846 epitope may be related to biosynthetic turnover of hyaline cartilage and the intervertebral discs but may also reflect progressive bone formation as a result of endochondral ossification. The correlation of the CPII:C2C ratio with CRP suggests that the CPII:C2C ratio might prove to be a useful marker of disease activity in AS.

Adult↗
PubMed2004

Genetic studies in familial ankylosing spondylitis susceptibility.

OBJECTIVE: To define the genetic basis of susceptibility to ankylosing spondylitis (AS), especially non-major histocompatibility complex (MHC) genes. METHODS: The study group comprised 244 affected sibling pairs from 180 pedigrees of primarily European ancestry. Sibling pairs were concordant for AS by the modified New York criteria and had available sacroiliac radiographs. The subjects were genotyped for 400 markers in ABI PRISM linkage map MD-10 and for 17 additional markers on chromosomes 6p, 6q, and 11q (including HLA-B, DRB1, DQA1, DQB1, and DPB1 alleles). Two-point and multipoint nonparametric linkage (NPL) analyses were conducted using the NPL statistic and 1-parameter allele-sharing model logarithm of odds (LOD) scores, calculated using the Allele-Sharing Model (ASM) computer program. RESULTS: Linkage of the MHC region was supported by both 2-point and multipoint analyses, with the strongest peak (45.90 cM) in the MHC at the HLA-DRB1 locus (NPL score 8.720, ASM LOD score 20.49; P = 6.8 x 10(-20) for 2-point analysis). A second region was found to have positive linkage at the q arm of chromosome 6 (D6S441) in 2-point analysis; this was supported by a 39.13-cM region (135.58-174.71 cM) in multipoint analysis, with the smallest P value (4.2 x 10(-3)) at 166.39 cM. A third region was found on chromosome 11q, with the strongest evidence for linkage for D11S4094 at 123 cM (NPL score 2.235, ASM LOD score 1.939) and, on transmission disequilibrium test analysis, D11S4090 at 105.74 cM (P = 6.2 x 10(-5)). Linkage in this area was supported by multipoint analysis, spanning 22.19 cM continuously from 101.68 cM to 123.87 cM, with the strongest peak at 112.33 cM (P = 0.014); this was confirmed by subsequent fine mapping studies. CONCLUSION: Thus, this genome-wide scan implicates, in addition to the MHC, regions outside the MHC in AS susceptibility, especially on chromosomes 6q and 11q.

Chromosome Mapping↗
PubMed2003

Novel genetic markers in the 5'-flanking region of ANKH are associated with ankylosing spondylitis.

OBJECTIVE: To use a candidate gene approach for the identification of genetic markers that are significantly linked to and associated with ankylosing spondylitis (AS). METHODS: We searched for novel polymorphisms in the ANKH gene (human homolog of the murine progressive ankylosis gene) and genotyped 2 polymorphic sites, one in the 5'-noncoding region and the other in the promoter region of ANKH, using DNA from affected (n = 273) and unaffected (n = 112) individuals from 124 AS families. We used these ANKH and other nearby polymorphisms to perform linkage and family-based association analyses. RESULTS: We identified 2 novel polymorphic sites: one in the 5'-noncoding region of ANKH involving 1-2 copies of an 8-bp repeat (denoted as ANKH-OR), and the other in the promoter region involving different copy numbers of a triplet repeat (denoted as ANKH-TR). ANKH-OR and ANKH-TR were in complete linkage disequilibrium. Five markers (D5S1953, ANKH-TR, ANKH-OR, D5S1954, and D5S1963) were used for both the linkage and association analyses. Multipoint linkage analysis of 124 AS families showed a modest level of significance (nonparametric linkage score 2.15; P = 0.015) at the ANKH region. The contribution of ANKH to AS susceptibility (lambda(s)) was 1.9. A family-based association study on the same AS families revealed that both ANKH-OR allele 1 and ANKH-TR allele 7 were significantly associated with disease, assuming an additive model (for ANKH-OR allele 1, P = 0.03; for ANKH-TR allele 7, P = 0.04). CONCLUSION: Our results indicate that ANKH-OR and ANKH-TR are novel genetic markers that are significantly associated with AS.

5' Flanking Region↗
PubMed2003

Canadian Rheumatology Association Consensus on the use of anti-tumor necrosis factor-alpha directed therapies in the treatment of spondyloarthritis.

Spondyloarthritis (SpA) represents a group of related arthritides characterized by their association with HLA-B27 and the development of sacroiliitis and enthesitis. Functional impairment, disability, and loss of quality of life may resemble that observed in rheumatoid arthritis. The SpA Research Consortium of Canada (SPARCC) is an informal association of rheumatologist members of the Canadian Rheumatology Association (CRA) with a special interest in therapeutics and outcomes research in SpA. Recent experience with anti-tumor necrosis factor-a (anti-TNF-a) directed therapies prompted a consensus-based evaluation of the evidence supporting their efficacy, safety, and appropriate use in SpA. We evaluated the clinical evidence in support of anti-TNF-a directed therapies in SpA. Medline was searched using appropriate keywords. Abstracts of the 1999-2002 annual meetings of the American College of Rheumatology and the European Congress of Rheumatology were extracted and admitted if sufficient detail was available to determine the level of evidence. Recommendations were based on randomized placebo-controlled trials (Level A evidence) and clinical studies without randomization (Level B evidence). Where the scientific literature was incomplete, recommendations reflected the consensus of SPARCC members (Level C evidence). Following development of an original draft document, consensus for revisions was achieved among members of SPARCC. The document was then posted on the CRA website prior to its final revision. The following recommendations have been endorsed by the Therapeutics Committee of the CRA: Infliximab and etanercept are indicated for reduction of signs and symptoms of moderate to severely active SpA in patients who have had an inadequate response to maximal doses of > or = 2 nonsteroidal antiinflammatory drugs (NSAID) over a 3-month period of observation; and either sulfasalazine or methotrexate is indicated in those with predominantly active peripheral arthritis. Current evidence supports their use as monotherapy (level of evidence A) for at least one year. NSAID and/or second line therapy with either sulfasalazine or methotrexate can be continued concomitantly. There is no evidence addressing potential advantages or disadvantages of combining methotrexate with anti-TNF therapy for SpA. Recommended doses for adults are: infliximab 5 mg/kg at 0, 2, and 6 weeks and every 8 weeks thereafter; etanercept 25 mg subcutaneously twice weekly. No therapy has been shown to slow progression of axial disease in SpA, and prognostic factors for determining response to therapy remain to be determined. It is the position of the CRA that all therapeutic options should be equally available according to the best judgments of the treating physician and the informed decision of the patient.

Antibodies, Monoclonal↗
PubMed2003

Should tetracycline treatment be used more extensively for rheumatoid arthritis? Metaanalysis demonstrates clinical benefit with reduction in disease activity.

OBJECTIVE: To compare the effectiveness of tetracycline antibiotics versus control (placebo or conventional treatment) in rheumatoid arthritis (RA) for the reduction of disease activity as defined by American College of Rheumatology criteria. METHODS: We searched Medline (1966-February 2002), Embase (1980-February 2002), and the Cochrane Controlled Trials Register (Issue 1, 2002 Cochrane Library). Reference lists of published trials were searched by hand for further identification of published reports and presentations at scientific meetings. Randomized controlled trials comparing tetracyclines to control (placebo or conventional disease modifying antirheumatic therapy) were selected for inclusion if at least one of the following outcomes was reported: tender joint count (TJC), swollen joint count, patient pain score by visual analog scale, patient global assessment of disease activity, physician global assessment of disease activity, eosinophil sedimentation rate (ESR) and C-reactive protein (CRP), joint space narrowing and erosions, adverse events, and quality of life as measured by the Health Assessment Questionnaire. Subjects were required to have RA as defined by the 1987 ARA criteria. RESULTS: Ten randomized controlled trials including 535 individuals were reviewed. Only 3 trials were considered high quality; elements of bias could not be excluded in the remainder. Tetracyclines, when administered for > or = 3 months, were associated with a significant reduction in disease activity in RA as follows: for TJC, standardized mean difference (SMD) = -0.39, 95% CI -0.74, -0.05; and for acute phase reactants, ESR, SMD = -8.96, 95% CI -14.51, -3.42. The treatment effect was more marked in the subgroup of patients with disease duration < 1 year who were seropositive. There was no absolute increased risk of adverse events associated with tetracyclines: absolute risk difference = 0.10, 95% confidence interval (CI) -0.01, 0.21. No beneficial effect was seen on radiological progression of disease: for erosions, SMD = 0.17, 95% CI -0.29, 0.64. In addition, subgroup analysis excluding trials with doxycycline showed that minocycline alone had a greater effect on reduction of disease activity: for TJC, SMD = -0.69, 95% CI -0.89, -0.49; and for ESR, SMD = -10.14, 95% CI -14.72, -5.57. CONCLUSION: Tetracyclines, in particular minocycline, were associated with a clinically significant improvement in disease activity in RA with no absolute increased risk of side effects. Unfortunately, the information available was inadequate to allow a detailed analysis of individual side effects in the studies. Further research is warranted to compare these agents to newer disease modifying drugs for comparable safety, efficacy, and cost-effectiveness.

Antirheumatic Agents↗
PubMed2002

Innate immunity in host-microbial interactions: beyond B27 in the spondyloarthropathies.

The spondyloarthropathies are diseases influenced by genetic predisposition and, to a varying extent, infectious triggers. A causal role for bacterial infections is most clear for reactive arthritis. Recent insights into arthritogenic components of bacteria may set the stage for a better understanding of disease pathogenesis, the role of heat shock proteins in antigen processing and immune activation, and the adjuvant effect of CpG-DNA. Recent developments in the area of innate immunity broaden current concepts of genetically defined factors in host-pathogen interactions. In particular, the biology of toll-like receptors as important elements in the innate immune response to pathogens is being defined. These factors in innate immunity may have important implications for sequelae of infections, such as reactive arthritis.

Animals↗