Stayin' alive: an introduction to survival analysis.
ABSTRACT In some studies, the outcome of interest is the time until some event occurs: readmission to hospital, the next manic episode, or even death. Survival analysis is a technique which can be used to analyze such data. It has added usefulness because it allows us to use data from subjects who drop out of sight over the course of the follow-up period as well as from those who do not experience the event by the time the study ends. This article introduces this technique and provides some guidelines for designing follow-up trials.
Full-textDOI: · Available from: David L Streiner, Aug 09, 2015
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ABSTRACT: Thesis (M.A.)--Simon Fraser University, 1997. Includes bibliographical references.
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ABSTRACT: To summarize the evidence on treatment withdrawal rates reported in observational studies and randomized controlled trials (RCTs) of methotrexate (MTX), parenteral gold (GST), sulphasalazine (SSZ) and hydroxychloroquine (HCQ) among patients with rheumatoid arthritis (RA). Two independent Medline searches were used to retrieve relevant studies published between 1966 and 1997. Those which disclosed information on the number of patients withdrawing from the drug were retained. Cumulative probabilities of survival on treatment were then computed using actuarial survival estimates, and differences were tested using log-rank, Wilcoxon and Cox proportional hazards tests. A total of 159 studies provided withdrawal information, and the numbers of patients who withdrew, in general or because of inefficacy or toxicity, could be abstracted from 110 studies contributing 142 treatment arms (MTX, 48; GST, 56; SSZ, 22; HCQ, 16). Data for HCQ were available only up to 24 months, but combined percentages of patients estimated to have continued MTX, GST or SSZ, respectively, for 60 months were 36, 23 and 22% when all failures were considered, 75, 73 and 53% when withdrawals due to lack of efficacy alone were considered, and 65, 36 and 48% when only withdrawals due to toxicity were taken into account. The Cox proportional hazards test performed on all withdrawals, after adjusting for year of publication and type of study, revealed that patients remained on MTX significantly longer than they did on the other three agents; however, the patients stayed significantly longer on GST than MTX when withdrawals for inefficacy were analysed separately. No significant differences in withdrawal rates were noted between observational studies and RCTs. Patients with RA stay significantly longer on MTX than on other disease-modifying anti-rheumatic drugs. Higher withdrawal rates among those given GST are mainly due to high toxicity, whereas the majority of withdrawals from SSZ and HCQ result from lack of efficacy. Withdrawal rates in observational studies are similar to those reported in RCTs.Rheumatology 10/2000; 39(9):975-81. DOI:10.1093/rheumatology/39.9.975 · 4.44 Impact Factor
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ABSTRACT: Although the evidence base for the use of antipsychotics in older people with schizophrenia is generally of low quality, it tends to support the use of atypical antipsychotics. Only limited information regarding longer term adherence to these apparently more effective drugs is available. The aim of this study was to determine predictors of adherence to risperidone or olanzapine in patients over 60. Patients receiving care from old age psychiatrists for their schizophrenia were randomised to treatment with olanzapine or risperidone and were followed for up to 3(1/2) years. Kaplan-Meier curves were generated to assess the univariate effect of randomisation drug on long-term adherence and Cox regression adjusted for baseline variables which may have affected adherence. In total, 60.6% of the 66 patients in the study were still taking their randomised drug by the end of the interval in which they remained under observation (64.7% olanzapine and 56.3% risperidone). This difference was non-significant. No baseline variable was associated with an increased risk of non-adherence, though the delivery form of pre-randomisation drug (oral or depot) was weakly (p = 0.054) associated with patients originally on depot being less likely to be adherent to an atypical drug. Overall adherence with atypical medication was good with almost two-thirds of the patients remaining on their randomisation drug for the interval in which they were under observation. Patients taken off depot were less likely to be adherent but there was no significant difference in adherence between olanzapine and risperidone. Scrutiny of the survival curves suggested that non-adherence is an early event in treatment and patients adherent at 6 months were likely to remain adherent over a longer time period.International Journal of Geriatric Psychiatry 04/2010; 25(4):411-8. DOI:10.1002/gps.2354 · 3.09 Impact Factor