Bayesian joint modelling of longitudinal and time to event data: a methodological review.

BACKGROUND: In clinical research, there is an increasing interest in joint modelling of longitudinal and time-to-event data, since it reduces bias in parameter estimation and increases the efficiency of statistical inference. Inference and prediction from frequentist approaches of joint models have been extensively reviewed, and due to the recent popularity of data-driven Bayesian approaches, a review on current Bayesian estimation of joint model is useful to draw recommendations for future researches. METHODS: We have undertaken a comprehensive review on Bayesian univariate and multivariate joint models. We focused on type of outcomes, model assumptions, association structure, estimation algorithm, dynamic prediction and software implementation. RESULTS: A total of 89 articles have been identified, consisting of 75 methodological and 14 applied articles. The most common approach to model the longitudinal and time-to-event outcomes jointly included linear mixed effect models with proportional hazards. A random effect association structure was generally used for linking the two sub-models. Markov Chain Monte Carlo (MCMC) algorithms were commonly used (93% articles) to estimate the model parameters. Only six articles were primarily focused on dynamic predictions for longitudinal or event-time outcomes. CONCLUSION: Methodologies for a wide variety of data types have been proposed; however the research is limited if the association between the two outcomes changes over time, and there is also lack of methods to determine the association structure in the absence of clinical background knowledge. Joint modelling has been proved to be beneficial in producing more accurate dynamic prediction; however, there is a lack of sufficient tools to validate the prediction.

Rapid immunoprofiling of cytokines, chemokines and growth factors in patients with active rheumatoid arthritis using Luminex Multiple Analyte Profiling technology for precision medicine.

OBJECTIVES: Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease of unknown etiology, characterised by symmetric erosive synovitis, leading inevitably to the destruction of cartilage and bone as well as bursa and tendon sheaths of joints. Our aim of this study was to decipher the differential expression of cytokines, chemokines and growth factors in the plasma of RA patients with active disease, using magnetic bead-based Luminex Multiple Analyte Profiling (xMAP) technology, for precision medicine. METHODS: We obtained plasma samples from RA patients (n=25) from the Rheumatology Clinic at the King Abdulaziz University Hospital (KAUH), Jeddah, Kingdom of Saudi Arabia (KSA) after written informed consent for their inclusion in this study. Besides, we have used the plasma samples from inflammatory osteoarthritis (OA) patients (n=10) and healthy volunteers (n=10) for comparison analyses. Plasma samples were examined using the Human Cytokine Magnetic 30-plex panel (Novex®), Invitrogen, USA) and analysed by MAGPIX® instrument (Luminex Corporation, USA). RESULTS: Though several pro-inflammatory cytokines, chemokines and growth factors present in the 30plex magnetic bead panel were not significantly (p>0.05) increased in the plasma of RA patients, the levels of plasma Th1 associated proinflammatory cytokines TNFα, and IL-6 and Th2 associated cytokines such as IL-4, IL-5 and IL-13 were significantly (p<0.05) upregulated compared to OA and normal controls. The proinflammatory IL-12 as well as anti-inflammatory IL-10 and IL-1RA were significantly (p<0.05) upregulated in the plasma of RA patients compared to normal controls. Also, the chemokines such as IP-10, RANTES and IL-8 as well as growth factors such as EGF, and VEGF were significantly (p<0.05) increased in RA. CONCLUSIONS: The MAGPIX data showed that the cytokines, chemokines and growth factors were differentially regulated systemically in patients with active RA compared to OA and normal controls. Hence, the Luminex xMAP technology-based multiplex immunoassays offer clues to formulate effective therapeutic strategies for RA patients with active disease irrespective of their treatment regimen and duration of treatment and, thus, an indispensable tool in precision medicine.