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V T Farewell

Publications and source records attributed to V T Farewell.

At least 19 recordsLinked to original sources
PubMed2001

Health-related quality of life of patients with psoriatic arthritis: a comparison with patients with rheumatoid arthritis.

OBJECTIVE: To compare health-related quality of life (QOL) between patients with psoriatic arthritis (PsA) and patients with rheumatoid arthritis (RA), using the Medical Outcomes Study Short Form health survey (SF-36) and the Health Assessment Questionnaire (HAQ). METHODS: Both the SF-36 and the HAQ were administered to 107 PsA patients attending the University of Toronto Psoriatic Arthritis Clinic between January 1 and December 31, 1994, and to 43 RA patients attending a University of Toronto-affiliated RA clinic during the same period. Standardized assessments of disease activity and severity were also performed at each clinic visit. Logistic regression analysis was used to compare health-related QOL between PsA and RA. RESULTS: Both patient populations experienced lower physical health compared with that of a general population sample. The RA patients demonstrated more active inflammatory disease at the time of assessment than the PsA patients. The PsA patients were younger, and more were men. Logistic regression analyses showed that patients with PsA reported higher levels of vitality than patients with RA, even after adjusting for the observed differences in clinical and demographic characteristics. PsA patients, however, reported more role limitations due to emotional problems and more bodily pain after adjusting for the difference in vitality and other covariates. CONCLUSIONS: Although both patient populations experienced reduced QOL, there were some meaningful differences in how the 2 conditions affect health-related QOL. Further, it appeared that there may be unique disabilities associated with the psoriasis dimension of PsA.

Adult↗
PubMed2001

HLA-DRB1*04 alleles in psoriatic arthritis: comparison with rheumatoid arthritis and healthy controls.

Psoriatic arthritis (PsA) is an inflammatory arthritis associated with psoriasis usually seronegative for rheumatoid factor. An increased frequency of HLA-DR4 has been noted in PsA, particularly among patients with a rheumatoid arthritis like (RA) arthritis. The aim of the current investigation was to compare HLA-DRB1*04 alleles in patients with PsA, patients with RA, and healthy controls. Sample size calculations based on the frequency of HLA-DR4 suggested that 90 individuals in each patient group would be sufficient to address our question. Therefore, 90 HLA-DRB1*04 positive patients from each patient group underwent high resolution molecular typing and were included in this study. Although HLA-DRB1*0401 was the most frequent allele in all groups, its frequency among the PsA patients was lower than that of RA patients and controls. HLA-DRB1*0402 was higher among patients with PsA. Patients with RA were more likely to have more than one shared epitope allele than either PsA or the healthy control group. HLA-DQB1 alleles did not contribute further information. We suggest that the differences in the class II HLA epitope(s) may also be related to interaction specificity with another molecule functioning in the immune response to a putative arthritogenic antigen and result in differences in disease expression.

Adult↗
PubMed2000

Human factors and cardiac surgery: a multicenter study.

OBJECTIVE: To study the role of human factors on surgical outcomes, with a series of 243 arterial switch operations performed by 21 surgeons taken as a model. METHODS: The following data were collected: patient-specific and procedural variables, self-assessment questionnaires, and a written report from a human factors researcher who observed the operation. The relationship of patient-specific variables to outcomes (death and death and/or near miss) was used to develop a multivariable baseline model to analyze the role of human factors after adjustment for these variables. RESULTS: The overall mortality was 6.6% with 24.3% of cases resulting in death and death and/or near misses. The self-assessment questionnaires were found to be unhelpful. Major and minor human failures were extracted from the written report. Major negative events were potentially life-threatening failures, whereas minor events were failures that, in isolation, were not expected to have serious consequences. Major events were closely related to death (P <.001) and death and/or near misses (P <.001). Appropriate compensation, however, sharply reduced the risk of death (P =.003). The total number of minor events was also closely related to both death and death and/or near misses (P <.001). CONCLUSION: The study highlights the role of human factors in negative surgical outcomes. Even in the most eventful circumstances, however, appropriate human factors defense mechanisms can lead to a successful outcome.

Cardiac Surgical Procedures↗
PubMed2000

Methods for assessing responsiveness: a critical review and recommendations.

A review of the literature suggests there are two major aspects of responsiveness. We define the first as "internal responsiveness," which characterizes the ability of a measure to change over a prespecified time frame, and the second as "external responsiveness, " which reflects the extent to which change in a measure relates to corresponding change in a reference measure of clinical or health status. The properties and interpretation of commonly used internal and external responsiveness statistics are examined. It is from the interpretation point of view that external responsiveness statistics are considered particularly attractive. The usefulness of regression models for assessing external responsiveness is also highlighted.

Arthritis, Psoriatic↗
PubMed2000

Risk factors for avascular necrosis of bone in patients with systemic lupus erythematosus: is there a role for antiphospholipid antibodies?

BACKGROUND: Avascular necrosis of bone (AVN) is a well known complication in patients with systemic lupus erythematosus (SLE). OBJECTIVE: To investigate the role of antiphospholipid antibody status (IgM and IgG anticardiolipin antibodies and lupus anticoagulant) with adjustment for corticosteroid use as risk factors for the development of AVN. METHODS: A cohort of 265 patients receiving long term follow up in our SLE clinic from 1978 to 1998 was analysed. Patients with AVN complications were detected and then matched for age, sex, ethnicity, duration of disease, and organ disease with two other patients with SLE. A further 31 patients were chosen at random for the analysis. RESULTS: Eleven patients had AVN, giving a point prevalence of 4%. There were no significant differences demonstrable in the presence of individual antiphospholipid antibodies (aPL) or their combination between the group with AVN or the two control groups. CONCLUSION: Incorporating an adjustment for corticosteroid use we were unable to show a link between the presence of aPL and the development of AVN in patients with SLE.

Adolescent↗
PubMed2000

Lost-to-follow-up study in systemic lupus erythematosus (SLE).

OBJECTIVE: To determine the extent of and reasons for lost-to-follow-up, as well as its impact on outcome studies in a cohort of lupus patients. METHODS: As of September 1991, 247 patients, in a cohort of 621 patients with SLE, being followed in a long-term prognosis study, had not been seen since 1 March, 1990 and were considered lost-to-follow-up. Patients were contacted and encouraged to return for an evaluation or to answer a questionnaire by telephone. Descriptive statistics were used to compare the lost-to-follow-up and non-lost-to-follow-up patients and the survival experience during the lost-to-follow-up period was compared with that when patients were not considered lost-to-follow-up. Estimated survival curves with and without the information gained through contacts with lost-to-follow-up patients were compared. RESULTS: Of the 247 patients, 29 have died, 66 returned for a full assessment, 84 completed a questionnaire and 68 (11%) were true lost-to-follow-up. The lost-to-follow-up patient group had 10% more Caucasians and 6% more males than the patients under regular follow-up. The estimated survival curves of the entire cohort with and without the new lost-to-follow-up data, calculated as of July 1992, were very similar. There was no evidence of a differential mortality rate during the period in which patients were lost-to-follow-up. Some suggestive evidence that the relative mortality rate comparing the rate during a period of lost-to-follow-up and during a period of active follow-up may depend on disease duration at the time of lost-to-follow-up was found. CONCLUSIONS: While it would be prudent to limit lost-to-follow-up as much as possible, especially for outcomes such as mortality which do not necessarily require a clinic visit, it does not appear that significant bias will be present in prospective studies based on our single clinic database. Since the retrieved 179 lost-to-follow-up patients did not affect survival studies it is likely that the 68 true lost-to-follow-up patients will also not have an impact on prognostic studies. Lupus (2000) 9, 363-367

Adolescent↗
PubMed2000

The relationship between patient satisfaction with health and clinical measures of function and disease status in patients with psoriatic arthritis.

OBJECTIVE: To investigate whether patient satisfaction with health is a distinct aspect of clinical or health status in a sample of patients with psoriatic arthritis (PsA). METHODS: One hundred sixty-nine consecutive outpatients attending the University of Toronto PsA Clinic completed the Arthritis Impact Measurement Scales II (AIMS2), which includes both a global rating of patient satisfaction with health and a scale that assesses satisfaction with functioning in 12 health domains. Clinical, laboratory, and radiological assessments of function, pain, inflammation, and damage were also performed according to a standard protocol. RESULTS: Logistic regression analysis indicated that the AIMS2 global ratings of patient satisfaction with health were not associated with traditional clinical measures of inflammation and damage, but were associated with American College of Rheumatology (ACR) functional class and number of fibromyalgia tender points. Patient satisfaction was also related to annual family income and use of retinoids or corticosteroids. Similarly, linear regression analysis showed that scores on the AIMS2 satisfaction scale were unrelated to traditional clinical measures of inflammation and damage, with the exception of total number of actively inflamed joints. ACR functional class, annual family income, and comorbidity were also related to scores on the satisfaction scale. CONCLUSION: Patient satisfaction with health appears to be relatively independent of traditional clinical measures of physical functioning, pain, and disease status.

Adult↗
PubMed1999

Conditional inference for predictive agreement.

We introduce the concept, and a measure of predictive agreement, tau, for two raters classifying items into q categories. The measure is based on the linear combination of log odds ratios from 2 x 2 subtables of a q x q cross-classification table. We show that analysis procedures for this measure, and transforms of it, can be based on conditional likelihood procedures. These procedures are exact, which is particularly helpful because of the small tabular cell frequencies which can typically arise with agreement data. To illustrate the advantages of the methodology, examples of typical agreement data arising from medical studies are considered. We demonstrate that the conditional likelihood function portrays the available sample information about tau, often more appropriately than the maximum likelihood estimate and an associated standard error. We highlight the value of combining information via likelihoods in an example involving 24 2 x 2 tables. An example involving three categories is used to illustrate that the methodology for the overall agreement measure can be adapted to examine relative agreement between pairs of categories.

Alcohol Drinking↗
PubMed1999

Monitoring paired binary surgical outcomes using cumulative sum charts.

Correlated binary data are encountered in many areas of medical research, system reliability and quality control. For monitoring failures rates in such situations, simultaneous bivariate cumulative sum (CUSUM) charts with the addition of secondary control limits are proposed. Using an approach based on a Markov chain model, the run length properties of such a monitoring scheme can be determined for sudden, or gradual, changes in the failure rates. The proposed control charts are easy to implement, and are shown to be very effective at detecting small changes in the rate of undesirable outcomes, especially when the changes are gradual. This procedure is illustrated using bivariate outcome data arising from a series of paediatric surgeries. The methodology is sufficiently general that it may be adapted for multivariate normal, binomial or Poisson responses.

Arteries↗
PubMed1999

New therapy explains the fall in AIDS incidence with a substantial rise in number of persons on treatment expected.

BACKGROUND: A marked decline in the number of reported AIDS cases has been observed in the United Kingdom, as in many industrialized countries, in 1996 and 1997. In England and Wales, a large reduction in AIDS cases has been recorded among homosexual and bisexual men. OBJECTIVES: To investigate, using data from the homosexuals and bisexuals in England and Wales as an example, possible explanations for the above decline such as the effects of new anti-retroviral therapies, or a decrease in the incidence of HIV in recent years. METHODS: A multistage model of HIV infection, HIV diagnosis, treatment and of AIDS diagnosis has been used to represent the pattern of HIV and AIDS incidence in homosexual and bisexual men in England and Wales up to the end of 1995. Scenarios for the post-1995 period were examined under different assumptions about changes in HIV incidence in recent years and treatment uptake and efficacy. RESULTS: The fall in the incidence of AIDS is unlikely to be the result of a reduction in HIV transmission during the 1990s. The most plausible explanation for this fall is the effect of new, more effective, anti-retroviral therapies. As a consequence, the number of individuals on treatment is likely to increase by 50 to 100% compared with the pre-1996 levels by the year 2001. Also, if the effect of the new therapies has a limited duration, or the use of such therapies is not well tolerated, the incidence of AIDS will rise again in the near future. CONCLUSIONS: These findings indicate that a substantial workload increase is under way for the healthcare system, and reiterate the need for measures to reduce HIV transmission as a means of bringing about a sustainable change in the incidence of AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1999

The utility of mixed-form likelihoods.

We highlight a feature of likelihood-based methods that provides flexibility in model formulation and inference. In particular, overall likelihoods that consist of likelihood contributions with different forms are considered. The particular forms may be predetermined by design criteria or may be selected based on features of the data. Inferences based on such mixed-form likelihoods are valid provided standard regularity conditions hold and the parameters of interest have the same interpretation in the various forms. The advantages of constructing overall likelihoods in this way are illustrated by applications involving the analysis of 2 x 2 x K tables and left-censored water quality data.

Biometry↗
PubMed1999

Progression in psoriatic arthritis: role of time varying clinical indicators.

OBJECTIVE: We have shown that the presence of 5 or more effusions and high medication use at first clinic visit predicted clinical progression in patients with psoriatic arthritis (PsA), while a low erythrocyte sedimentation rate (ESR) was "protective." These clinical indicators will change over the course of a patient's disease. We investigated whether there is additional prognostic information available through monitoring these indicators at each clinic visit. METHODS: A total of 365 patients with at least 2 followup visits at the PsA Clinic who did not have 10 or more damaged joints at first visit were included. Clinical assessments including the number of actively inflamed and damaged joints were carried out every 6-12 mo according to a standard protocol. The analysis used a generalized linear model that relates the number of damaged joints that developed between consecutive clinic visits to the information available at the first of the 2 visits, and in which the information was added to a baseline model including the first visit variables previously shown to be important. RESULTS: Single factor analysis suggested that the addition of functional class, number of actively inflamed joints, and Lansbury index provide prognostic information for subsequent damage. The final multivariate model includes time varying information on the number of actively inflamed joints, functional class, and current damage, as well as first visit information on prior medication as predictive of progression of damage, plus male sex and a low ESR at first visit as "protective." CONCLUSION: Time varying predictors for damage are important and should be monitored longitudinally in patients with PsA.

Adolescent↗
PubMed1998

Mortality studies in psoriatic arthritis: results from a single outpatient center. II. Prognostic indicators for death.

OBJECTIVE: To investigate prognostic factors associated with mortality in patients with psoriatic arthritis (PsA). METHODS: Patients followed up at the Toronto PsA Clinic between 1978 and 1994 were included. Patients were reviewed at initial clinic entry and at 6-month intervals using a standard protocol. Data on deaths were collected in a prospective manner, and death certificates were used to identify the primary and antecedent cause(s) of death. All death information was recorded in the clinic's computerized database. Only factors that represented standard clinical measures of disease activity and progression were studied. The relationship between potential prognostic factors recorded at the time of the first clinic visit and the mortality rate was determined using the Cox relative risk regression model. RESULTS: There were 428 patients (234 men and 194 women), of whom 68% were known to be alive on September 1, 1994, 20% were lost to followup but assumed to be alive, and 12% had died. Multivariate analysis revealed that an erythrocyte sedimentation rate (ESR) > 15 mm/hour, medications used prior to initial clinic visit, radiologic damage, and the absence of nail lesions were associated with an increased overall mortality rate. There is some suggestion that prior medication use was least important for deaths associated with the circulatory system, while radiologic damage was particularly important for such deaths. A marked sex-associated effect was noted among deaths caused by injuries/poisoning, since 6 of the deaths occurred in men and only 1 was in a woman. CONCLUSION: Patients with PsA are at an increased risk of death compared with the general population. Evidence of previously active and severe disease, as manifested by the prior use of medications and by radiologic changes as well as an elevated ESR at presentation, are prognostic indicators for death. The presence of nail lesions appears to be a protective factor that has the most clinical importance in the context of previously active and severe disease.

Adolescent↗
PubMed1998

HLA markers and progression in psoriatic arthritis.

OBJECTIVE: To investigate whether the addition of all serologically defined HLA antigens to a baseline model further influences the predisposition to disease progression in psoriatic arthritis (PsA). METHODS: Patients with PsA followed prospectively over 19 years were studied. Clinical and laboratory assessments of both active inflammation and clinical damage were performed at 6 month intervals according to a standard protocol. Progression of damage was defined as transition to higher damage states defined by the number of damaged joints. A model that provides estimates of the ratio of transition rates for an individual with the antigen versus one without, and examines the antigen effect on each of the 3 transition rates, was used. HLA antigens were examined in groups by loci under the assumption of common effects across transitions when added to the basic model. The significance levels were examined in comparison with Bonferroni type corrections. Likelihood ratio chi-squared statistics were used as a basis for the significance levels. In total, 292 patients with PsA were included in the study. RESULTS: Only HLA-B22 was added to the original model, which includes HLA-B39, providing risk for progression in early stages, HLA-B27 in the presence of HLA-DR7 providing risk for progression through all states, and DQw3 providing increased risk in the absence of DR7, while in the presence of DR7 it provides "protection." HLA-B22 provides protection from disease progression through all states. CONCLUSION: This study extends our report that HLA antigens serve as markers for disease progression in PsA.

Adolescent↗
PubMed1998

Radiographic reports in osteonecrosis of the hip in systemic lupus erythematosus.

The purpose of this study was to assess the reliability and accuracy of the modified Marcus and Enneking classification of osteonecrosis of the femoral head in patients with systemic lupus erythematosus when applied to the reading of the original radiographs and then applied to interpreting the radiologist's written report. Thirty anteroposterior radiographs of the hip from patients with systemic lupus erythematosus with varying degrees of osteonecrosis were selected and submitted to a panel of two rheumatologists and an orthopaedic surgeon who individually graded the radiographs using the modified Marcus and Enneking method. Agreement was determined by the kappa statistics. Identical staging was assigned in 21 of the 30 radiographs by all three observers, providing a weighted kappa of 0.88. Identical staging was assigned by all three observers in 26 of the 30 reports, giving a kappa of 0.95. There was agreement in the staging of 23 of the 30 radiographs by actual reading and the radiologist's report, with a weighted kappa of 0.86. Discordant gradings resulted primarily because the Marcus and Enneking method does not account for degenerative changes on the femoral side of the hip joint. The authors conclude that the radiologist's report can be used to stage osteonecrosis when interpreted by expert observers and when those reports contain all critical information required for staging. The authors recommend that the Marcus and Enneking classification be modified to include changes on the femoral side of the joint.

Femur Head Necrosis↗
PubMed1998

Responsiveness of health status instruments to changes in articular status and perceived health in patients with psoriatic arthritis.

OBJECTIVE: To compare the responsiveness of the Health Assessment Questionnaire (HAQ), Arthritis Impact Measurement Scale 2 (AIMS2), and Medical Outcome Study Short Form Health Survey (SF-36) to changes in articular status and perceived health in outpatients with psoriatic arthritis (PsA). METHODS: The 3 health status instruments were administered in random order on 2 occasions, about 12-18 months apart, to 70 patients attending the University of Toronto psoriatic arthritis clinic. Standardized assessments of disease activity, disease severity, and general health perceptions were also performed at each clinic visit. To assess responsiveness we used: (1) linear regression analyses to relate change scores for perceived health, the number of actively inflamed, and damaged joints to change scores for selected dimensions of the HAQ, AIMS2, and SF-36; (2) logistic regression analyses to relate both improvement in disease activity and disease progression to health status change scores; and (3) standardized response means (SRM). RESULTS: There were 43 men and 27 women with a mean age of 46 years and arthritis duration of 13 years. Univariate regression analyses showed that the individual instruments were responsive to perceived changes in health, but relatively insensitive to detect changes in articular status. Multivariate regression analyses, in which the common dimensions of the instruments were jointly entered, indicated the SF-36 was equally or more responsive to changes in number of actively inflamed joints, clinical improvement in disease activity, and perceived health than the HAQ and AIMS2. The SRM analysis also suggested that the SF-36 was the most responsive. CONCLUSION: The SF-36 proved equally or more responsive to short term changes in perceived health and inflammatory disease activity; however, none of the instruments showed responsiveness to disease progression.

Adult↗
PubMed1997

A Markov model for HIV disease progression including the effect of HIV diagnosis and treatment: application to AIDS prediction in England and Wales.

Back-calculation is a widely used method to estimate HIV incidence rates, and is commonly based on times of AIDS diagnosis. Following up earlier work, we extend this method to also incorporate knowledge of times of HIV diagnosis (first positive test). This is achieved through the use of a Markov model which describes the progress of an HIV infected person through various stages, and which allows causal connections between events to be explicitly modelled. Estimation is based on maximum likelihood, the likelihood being calculated within a discretized version of the Markov model. The effect of sampling uncertainty and model uncertainty (sensitivity) is evaluated simultaneously by means of a combined bootstrap and simulation procedure. At each replication we resample both the data and the model (from a set of possible models described by randomizing one or more parameters). For instance, uncertain knowledge about the incubation distribution affects the estimates of some parameters, but not others. The Markov approach is applied to the prediction of AIDS incidence for homosexuals in England and Wales up to the year 2000.

AIDS Serodiagnosis↗