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In many studies, interest lies in determining whether members of the study population will undergo a particular event of interest. Such scenarios are often termed 'mover-stayer' scenarios, and interest lies in modelling two sub-populations of 'movers' (those who have a propensity to undergo the event of interest) and 'stayers' (those who do not). In general, mover-stayer scenarios within data sets are accounted for through the use of mixture distributions, and in this paper, we investigate the use of various random effects distributions for this purpose. Using data from the University of Toronto psoriatic arthritis clinic, we present a multi-state model to describe the progression of clinical damage in hand joints of patients with psoriatic arthritis. We consider the use of mover-stayer gamma, inverse Gaussian and compound Poisson distributions to account for both the correlation amongst joint locations and the possible mover-stayer situation with regard to clinical hand joint damage. We compare the fits obtained from these models and discuss the extent to which a mover-stayer scenario exists in these data. Furthermore, we fit a mover-stayer model that allows a dependence of the probability of a patient being a stayer on a patient-level explanatory variable. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Motivated by investigations of factors related to various patient-reported outcome measures in psoriatic arthritis patients, after controlling for the effect of disease activity on these outcomes, we outline an approach for dealing with a rapidly fluctuating explanatory variable in a multistate model. On the basis of a representation of this variable as an ordinal classification, we suggest the use of an expanded multistate model. We examine the bias in estimating effects associated with other variables via simulation for different modelling choices. We present an analysis of a motivating data set on physical functional disability in psoriatic arthritis patients. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Objective: To investigate how cirrhosis-biased referral to liver clinics can explain the wide variation in progression rates for differently recruited cohorts and, in particular, for liver clinic cohorts compared to community-based studies of the natural history of hepatitis C virus (HCV).Study Design and Setting: A simulation was designed to illustrate the sort of referral bias pattern that is capable of converting a 20-year progression rate to cirrhosis of around 5% in the community of HCV-infected individuals into a 20% progression rate for patients who have been selectively referred to a liver clinic.Results: We show that event-biased recruitment, such as occurs if referral to liver clinics is increasingly likely the closer a patient is to cirrhosis, can produce severely upwardly biased estimates of progression rates, can dampen the influence of "poor prognostic" factors (such as history of excessive alcohol consumption), but overrepresents the proportion of patients in the community of HCV-infected individuals who have poor prognosis.Conclusion: When attempting to establish the natural history of new diseases with long incubation periods, researchers should be on the look out for potential biases that result from the way patients are referred into clinical cohorts. [ABSTRACT FROM AUTHOR]

It is well established that significant numbers of prisoners have psychosis, yet little is known of what happens to them over time. One hundred and forty prisoners with probable psychosis from the National Survey of Psychiatric Morbidity in Prisons were re-interviewed at one-year follow-up. During the follow-up year 10% (95% CI 2-17) were admitted to hospitals, detox or medium secure units. At follow-up, 65% (95% CI 52-77) had ‘caseness’ levels of current psychiatric illness, but less than a quarter had appointments with psychiatric professionals: for violent or sexual offenders, only 41% had such appointments. Three per cent of those released were in supported accommodation at follow-up. [ABSTRACT FROM AUTHOR]

Background/Aims: Increased rates of bone loss and fracture have been reported after liver transplantation. The aim of this study was to investigate the effects of a pre-transplant infusion of pamidronate on fracture incidence and bone loss during the first year after transplantation.Methods: Ninety-nine adults awaiting orthotopic liver transplantation (OLT) were randomised to pamidronate or no treatment. Spinal X-rays were obtained at baseline and after 12 months. Bone mineral density (BMD) was measured at the lumbar spine (L1–4) and femoral neck at baseline, and 3, 6, and 12 months after OLT.Results: The incidence of fractures in the first year after OLT was 8%, four patients within the pamidronate treated group and two in the untreated group developing fractures (P=0.40). No significant spinal bone loss occurred in either group during the first year. However, significant and sustained bone loss occurred at the femoral neck in both groups. No significant differences were seen between pamidronate treated or untreated groups at either site.Conclusions: Pamidronate in the regimen used had no significant effect on fracture rate or BMD post-transplant. The low incidence of fracture and absence of spinal bone loss indicate that bone disease after liver transplantation may be less common than previously reported. [Copyright &y& Elsevier]

Identifies an index of mobility-related limitations composed of physiological measures that are associated with reported mobility disability in elders. Groups of disability in older people; Analysis of the third National Health and Nutrition Examination Survey; Comparison of receiver operating characteristic curves between subsamples in difficulty and inability models.