slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Short and long term prognosis of disability in Multiple Sclerosis Some Tools, Models and Validation PowerPoint Presentation
Download Presentation
Short and long term prognosis of disability in Multiple Sclerosis Some Tools, Models and Validation

Loading in 2 Seconds...

play fullscreen
1 / 46

Short and long term prognosis of disability in Multiple Sclerosis Some Tools, Models and Validation - PowerPoint PPT Presentation


  • 555 Views
  • Uploaded on

Short and long term prognosis of disability in Multiple Sclerosis Some Tools, Models and Validation. A. Neuhaus, M. Daumer. Outline. Background about MS Online Analytical Processing Tool “Risk Profile” Segmented Regression and Correction for Error Validation Strategy & examples.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

Short and long term prognosis of disability in Multiple Sclerosis Some Tools, Models and Validation


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
    Presentation Transcript
    1. Short and long term prognosis of disability in Multiple Sclerosis Some Tools, Models and Validation A. Neuhaus, M. Daumer

    2. Outline • Background about MS • Online Analytical Processing Tool “Risk Profile” • Segmented Regression and Correction for Error • Validation Strategy & examples

    3. Background Multiple Sclerosis (MS) • common neurological degenerative disease • 2.5 million people affected worldwide • drugs have shown efficacy on short-term outcomes • agents are by no means ‘cure’ – many patients have disease activity • long term determination of efficacy is necessary

    4. Background Multiple Sclerosis (MS) Cause CNS Disease courses Multiple Sclerosis Disability MRI Relapse

    5. Background Multiple Sclerosis (MS) Cause • Specific cause is unknown • female : male = 2 : 1 • more common in Caucasians • autoimmune process • environmental factors • genetic predisposition CNS Disease courses MRI Disability MRI Relapse http://medstat.med.utah.edu

    6. Background Multiple Sclerosis (MS) Cause unknown CNS Disease courses Disability MRI Relapse http://www.msdecisions.org.uk

    7. Background Multiple Sclerosis (MS) Cause unknown CNS Disease courses Number of enhancing lesions Lesion Volume Disability MRI Relapse

    8. Background Multiple Sclerosis (MS) Cause unknown CNS • Sudden failures in functional systems • Recovery after a few days or weeks • vision problems • problems with walking • tremor • difficulties with speech • fatigue • bladder and bowel problems Disease courses Disability MRI Relapse

    9. Background Multiple Sclerosis (MS) Cause unknown CNS Disease courses Disability MRI Relapse sudden failures

    10. Relapsing Remitting disability time Clinically Isolated Syndrome Primary Progressive Secondary Progressive disability disability disability time time time Background Multiple Sclerosis (MS) Cause unknown CNS Disease courses Disability MRI EDSS Relapse sudden failures

    11. Outline • Background • OnLine Analytical Processing Tool • Segmented Regression and Correction for Error • Improvement of Outcome Measures • Validation Strategies

    12. OLAP Aim • Make the database of the SLCMSR (20.000 patients, 45 data sets)available to health care professionals via the internet • Identification of database subgroups based on clinical parameters • Statistical analyses of subgroups • Illustration of future disease course of subgroups

    13. OLAP Tool • OnLine Analytical Processing Tool (OLAP-Tool) • accessible via the internet • no need for data transfer • no need for local software installation • server based on Java and R • Individual Risk Profile (IRP) • 1059 MS patients from placebo arms of controlled clinical trials • definition of patient profile • display the course of database patients with same characteristics

    14. 4 20 20 10 4 64.000 combinations OLAP Hurdles • Patient profile can be defined by combining Age at MS onset Disease Duration Number of Relapses EDSS Course ? 1.059 patients

    15. OLAP Hurdles • if a few or no matching patients are found … weight characteristics according to their importance determine weights by means of: number of relapses in the first year increase of disability Linear Regression Poisson Regression

    16. OLAP Selection of most similar patients

    17. OLAP Outcomes

    18. OLAP Outcomes

    19. OLAP Outcomes

    20. OLAP Next steps • Evaluate performance of expert opinion vs. tool/model (“Validation”) • Include patient history & treatment data • Develop and validate models for predicting treatment (non-)responders • OLAP tool for evidence based decision support when to switch treatment(“Disease Management”) • Prospective evaluation in a clinical trial if promising Similar to path taken for CTG monitoring

    21. Outline • Background • OnLine Analytical Processing Tool • Segmented Regression and Correction for Error • Improvement of Outcome Measures • Validation Strategies

    22. secondary progressive phase relapsing remitting phase disability time Models Problem • What are the factors affecting the start of the progressive phase? • What are the factors predicting subsequent disability best? Joint work with J. Noseworthy, Mayo clinic, Rochester, USA, L. Kappos, Basel, CH, T. Augustin & H. Küchenhoff, LMU, Munich, Germany

    23. Models Restrictions to data • Patients in the first phase of the disease (RRMS) • disability level < 6.5 • inclusion in a controlled clinical trial • at least 4 observations in longitudinal data • complete data in covariates 355 RRMS patients from placebo arms of 16 clinical trials

    24. Models Data Mean S.D. Range Female to male ratio 2.7 Age of onset (years) 28.3 7.0 13 – 48 Disease duration before entry (years) 7.0 6.1 0.7 – 34.8 Observation period (months) 26.6 12.7 2.8 – 59.3 EDSS score at entry 2.7 1.4 0 – 6 Relapse rate 2 years prior study 1.5 0.7 0 – 4

    25. Models Methods • Two – Step – Analysis EDSS Segmented Regression Model Time to progressive phase Survival Analysis (with error correction) Predictive factors

    26. -1 ' p     1 (tj - )+ -Itj>  1 (tj - )+ -Itj>  '  p - 3 Cov = j = 1 Models Methods / Segmented Regression Model • piecewise linear regression model describes disease process D Dβ(t) =  + β (t-)+ 0  10, β > 0,  > 0 and (t-)+ = max(0, t-) • dispersion of estimates

    27. Models Methods / Survival Analysis • Correct determination of time of change is impossible • , estimated time to progression, is overlaid by an error e • magnitude of the error will be considered in the survival model • Assumptions: • true, but unknown, event times t follow a Weibull distribution • relation between  and e: = t · e, t  e •  log  =log t + log e • log  = x´β + ( + ),  = -1 log e • exp - ~ (,) • Survival function follows a Burr distribution S() = [1 + {exp(-x')}-1 -2 2]-2-2 2 = var (log ) and  = 2 -2

    28. . . . l() = wi = (1 + -2 i2 exp(zi))-1 where and zi = (log(i) - xi')-1 d d i log (1 – S(i))   log S(ci) + l() = i  censored i  event n  i = 1 ceni zi - log(i) + log(wi/) + 2i-2 log(wi) Models Methods / Survival Analysis • Regression parameter are specified using maximum likelihood estimation • The log-likelihood is given by

    29. Models Methods / Survival Analysis Error adjusted regression Weibull regression Parameter Std.Error p-Value Parameter Std.Error p-Value Intercept 6.86 0.25 <0.001 7.59 0.22 <0.001 Relapse rate 0.20 0.11 0.08 EDSS -0.10 0.06 0.07 -0.15 0.07 0.02 Log (scale) -0.08 0.07 0.22 0.02 0.09 0.84 Scale 0.92 0.98 The higher the EDSS level, the shorter the time to progression. Higher relapse rate – longer time to progression? Importance of relapse rate instable.

    30. Models Methods / Survival Analysis

    31. Outline • Background • OnLine Analytical Processing Tool • Segmented Regression and Correction for Error • Improvement of Outcome Measures • Validation Strategies

    32. Validation Need for validation – Model selection • Over-fitting of data • Scenario • Many models checked for describing data set • Model with best fit is used for further analyses • Model fit is tested using standard statistical methodology • Result • Danger of over-fitting since model selection and model validation is based on same dataset • Danger enhanced if method applied to small subgroups

    33. Validation Need for validation – Data driven hypotheses • Theory • Neither the model nor the hypothesis to be tested should be data driven • Practice • Data are visualized before models are fit and, frequently, before hypotheses are formulated • Effect • “Promising” hypotheses are being tested • Actual level of tests far exceed nominal levels, leading to a large number of “false positive” results

    34. Validation Our strategy: Splitting of data set Open part Closed part „Confirmation or validation sample“ „Learning or training sample“ Development of tools Statistical analyses Confirmationof findings - Final result Free investigation of data set Significant results

    35. Validation SLCMSR Database Inclusion/exclusion criteria Plausibility check Harmonization/homogenization Pooling Split into training sample (~40%) and validation sample (~50%) Analysis / modeling ~ 10 % Mixing sample ~ 40 % ~ 50 % Training sample Validation sample

    36. Validation Validation Procedure • Validation concept + validation results of „open“ part of SLCMSR database are sent to Validation Committee • Validation Committee approves proposed validation concept or alternately suggests specific modifications for consideration by the authors of the project • Data trustee executes analysis agreed upon by Validation Committee and authors, programming code is provided by project team • Validation Committee and authors agree upon formulation of results summary

    37. Validation Examples • Relapses and subsequent worsening of disability in RRMS • Occurrence of relapses in the first 3 months on study appeared to be the best predictor for a shorter subsequent time to sustained increase of the EDSS. • Signif. even after “naïve” Bonferroni adjustment for multiple testing. • BUT: Unable to validate this on an independent (validation) part of the SLCMSR dataset: relationship between relapses and subsequent disability either non-existent or very weak • Correlating T2 lesion burden on MRI with the clinical manifestations of multiple sclerosis (Li, Held et al, submitted to Neurology) • Question: How does one validate a plateauing relationship? • Visualization, with CI for Spearman‘s correlation coefficient and • significant improvement in model fit with non-linear approach • Validation was successful: there is a plateau, lesion load doesn’t increase with disability, no good surrogate marker

    38. Validation Examples How to predict on-study relapse rate? (Held et al, Neurology, in press)  validation was successful: pre-study relapse rate is the most important predictor for future relapse rate. MRI information doesn’t add much.

    39. Validation Invited Session for IBC 2006, Montreal • Session organizers: M. Daumer, U. Held (SLCMSR) • Discussant: John Petkau (Prof. of Statistics, UBC, Vancouver) • Speakers: • Trevor Hastie (Prof. of Statistics, Stanford University) „Validation in Genomics“ • Ulrike Held (SLCMSR) „Validation Procedure of the SLCMSR: Methodological and Practical Aspects“ • Martin Schumacher (Prof. of Biometry, Freiburg University, GER) „Assessment and Validation of Risk Prediction Models“

    40. Validation

    41. Literature Barkhof F, Held U, Simon JH, Daumer M, Fazekas F, Filippi M, Frank JA, Kappos L, Li D, Menzler S, Miller DH, Petkau J, Wolinsky J. Predicting gadolinium-enhancement status in MS patients eligible for randomized clinical trials. Neurology in press Compston A, Ebers G, Lassmann H, McDonald I, Matthews B, Wekerle H. Mc Alpines Multiple Sclerosis 3rd Edition, Churchill Livingstone, 1998. Freedman MS, Patry DG, Grand'Maison F, Myles ML, Paty DW, Selchen DH. Treatment optimization in multiple sclerosis, Can J Neurol Sci 33 (2):157-68, 2004. Held U, Heigenhauser L, Shang C, Kappos L, Polman C. Predictors of relapse rate in MS clinical trials. Neurology in press Küchenhoff H. An exact algorithm for estimating breakpoints in segmented generalized linear models, Computational Statistics 12, 235 – 247, 1997. Kurtzke JF. Rating neurologic impairment in multiple sclerosis: An expanded disability status scale (EDSS), Neurology 33(11):1444-52, Nov. 1983. Pittock SJ, Mayr WT, McClelland RL, Jorgensen NW, Weigand SD, Noseworthy JH, Weinshenker BG, and Rodriguez M. Change in MS-related disability in a population-based cohort: A 10-year follow-up study. Neurology 62: 51-59, 2004. Hellriegel B, Daumer M, Neiß A. Analysing the course of multiple sclerosis with segmented regression models, Tech. rep., Ludwig-Maximilians-University Munich, SFB Discussion Paper, 2003. Skinner CJ, Humphreys K. Weibull Regression for Lifetimes Measured with Error, Lifetime Data Analysis 5, 23-37, 1999. Neuhaus A. Modelling Time to Progression in Multiple Sclerosis, Diploma Thesis, Ludwig-Maximilians-University Munich, http://www.slcmsr.org, 2004 Schach S, Daumer M, Neiß A. Maintaining high quality of statistical evaluations based on the SLCMSR data base - Validation Policy, http://www.slcmsr.org. Ioannidis PDA. Why most publishes research findings are false, PLoS Med 2(8): e124, 2005. Ioannidis PDA. Microarrays and molecular research: noise discovery?, Lancet 365: 454-55, 2005.

    42. Outline • Background • OnLine Analytical Processing Tool • Segmented Regression and Correction for Error • Improvement of Outcome Measures • Validation Strategies

    43. Outcome Measures • Time to progression • Time to sustained worsening/progression • widely used outcome measure in Phase III clinical trials • outcome depends on confirmation period • effective study duration is shortened since last visit(s) can only be used as confirmation

    44. non-confirmed worsening confirmed worsening no worsening no worsening non-confirmed worsening confirmed worsening confirmed worsening no worsening Outcome Measures • Definition of sustained worsening divides cohort in 3 groups • current procedure • What about … ? • consideration of confirmation period • consideration of visit schedule

    45. Logit Model Cox Model Proportion matched to confirmed worsening Proportion matched to confirmed worsening Proportion matched to confirmed worsening Proportion matched to confirmed worsening Outcome Measures • random matching of ‘non-confirmed worsening’ to one of the other groups Estimation based on standard definition Estimation without non-confirmed patients room for improvement

    46. Models Methods / Segmented Regression Model n = 158 n = 129 n = 68 within observation period 1.2 y +/- 1.0 y [0.01 y – 4.6 y] Prior to first observation after last observation 1.9 y +/- 1.1 y * [0.2 y – 4.6 y] Estimated start of progressive phase * censoring times