Chronic non-specific low back pain - sub-groups or a single mechanism?

Copyright 2008 Wand and O'Connell; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Background: Low back pain is a substantial health problem and has subsequently attracted a considerable amount of research. Clinical trials evaluating the efficacy of a variety of interventions for chronic non-specific low back pain indicate limited effectiveness for most commonly applied interventions and approaches. Discussion: Many clinicians challenge the results of clinical trials as they feel that this lack of effectiveness is at odds with their clinical experience of managing patients with back pain. A common explanation for this discrepancy is the perceived heterogeneity of patients with chronic non-specific low back pain. It is felt that the effects of treatment may be diluted by the application of a single intervention to a complex, heterogeneous group with diverse treatment needs. This argument presupposes that current treatment is effective when applied to the correct patient. An alternative perspective is that the clinical trials are correct and current treatments have limited efficacy. Preoccupation with sub-grouping may stifle engagement with this view and it is important that the sub-grouping paradigm is closely examined. This paper argues that there are numerous problems with the sub-grouping approach and that it may not be an important reason for the disappointing results of clinical trials. We propose instead that current treatment may be ineffective because it has been misdirected. Recent evidence that demonstrates changes within the brain in chronic low back pain sufferers raises the possibility that persistent back pain may be a problem of cortical reorganisation and degeneration. This perspective offers interesting insights into the chronic low back pain experience and suggests alternative models of intervention. Summary: The disappointing results of clinical research are commonly explained by the failure of researchers to adequately attend to sub-grouping of the chronic non-specific low back pain population. Alternatively, current approaches may be ineffective and clinicians and researchers may need to radically rethink the nature of the problem and how it should best be managed

Improving Ocean Model Initialization for Coupled Tropical Cyclone Forecast Models Using GODAE Nowcasts

Abstract To simulate tropical cyclone (TC) intensification, coupled ocean–atmosphere prediction models must realistically reproduce the magnitude and pattern of storm-forced sea surface temperature (SST) cooling. The potential for the ocean to support intensification depends on the thermal energy available to the storm, which in turn depends on both the temperature and thickness of the upper-ocean warm layer. The ocean heat content (OHC) is used as an index of this potential. Large differences in available thermal energy associated with energetic boundary currents and ocean eddies require their accurate initialization in ocean models. Two generations of the experimental U.S. Navy ocean nowcast–forecast system based on the Hybrid Coordinate Ocean Model (HYCOM) are evaluated for this purpose in the NW Caribbean Sea and Gulf of Mexico prior to Hurricanes Isidore and Lili (2002), Ivan (2004), and Katrina (2005). Evaluations are conducted by comparison to in situ measurements, the navy’s three-dimensional Modular Ocean Data Assimilation System (MODAS) temperature and salinity analyses, microwave satellite SST, and fields of OHC and 26°C isotherm depth derived from satellite altimetry. Both nowcast–forecast systems represent the position of important oceanographic features with reasonable accuracy. Initial fields provided by the first-generation product had a large upper-ocean cold bias because the nowcast was initialized from a biased older-model run. SST response in a free-running Isidore simulation is improved by using initial and boundary fields with reduced cold bias generated from a HYCOM nowcast that relaxed model fields to MODAS analyses. A new climatological initialization procedure used for the second-generation nowcast system tended to reduce the cold bias, but the nowcast still could not adequately reproduce anomalously warm conditions present before all storms within the first few months following nowcast initialization. The initial cold biases in both nowcast products tended to decrease with time. A realistic free-running HYCOM simulation of the ocean response to Ivan illustrates the critical importance of correctly initializing both warm-core rings and cold-core eddies to correctly simulate the magnitude and pattern of SST cooling

The assessment of functional status in rheumatoid arthritis: A cross cultural, longitudinal comparison of the Health Assessment Questionnaire and the Groningen Activity Restriction Scale

Objective. To compare a disease specific measure of functional status, the Health Assessment Questionnaire (HAQ) with a generic measure of functional status, the Groningen Activity Restriction Scale (GARS) in a cross cultural and longitudinal setting. Besides the comparison of psychometric properties, sex differences were also studied. Methods. In a sample of 634 patients with rheumatoid arthritis (RA) (290 from The Netherlands, 116 from France, 228 from Norway), the psychometric properties (Cronbach's alpha and rho) of the GARS and the HAQ were compared among countries. The sensitivity for change between TI and T2 was tested by means of the standardized response mean for a one year followup; furthermore, the relative efficiency of both instruments was computed. A t test was used to trace sex differences. Results. The psychometric properties of both the HAQ and the GARS were very good. Both form unidimensional scales of hierarchically ordered items; alpha and rho are >0.91 for both instruments. For patients who improved between T1 and T2, measured by the Ritchie Articular Index, the standardized response mean of the HAQ and the GARS were moderate, whereas for patients who worsened, the standardized response means were small. The results based on the relative efficiency were ambiguous. Furthermore, the mean score for women on the HAQ was 0.25 higher in contrast to scores for men. The GARS did not yield different scores for women and men. Conclusion. The internal consistency of the GARS and the HAQ are comparable. The HAQ has yielded different results for women and men. Therefore, when the HAQ is used, sex differences should be taken into account. With respect to sensitivity to change, the GARS and the HAQ obtained much better results for patients who improved in contrast to patients who worsened. The GARS was found to be more sensitive to change for patients who improved

A comparison of sequential assimilation schemes for ocean prediction with the HYbrid Coordinate Ocean Model (HYCOM): Twin experiments with static forecast error covariances

► Four covariance matrix approximations for data assimilation with HYCOM are compared. ► Assimilation into HYCOM is most effectively done in the native generalized coordinates. ► 3D covariances perform better than vertically decoupled and separable 2D covariances. ► Surface information alone is insufficient to correct salinity and temperature at depth. We assess and compare four sequential data assimilation methods developed for HYCOM in an identical twin experiment framework. The methods considered are Multi-variate Optimal Interpolation (MVOI), Ensemble Optimal Interpolation (EnOI), the fixed basis version of the Singular Evolutive Extended Kalman Filter (SEEK) and the Ensemble Reduced Order Information Filter (EnROIF). All methods can be classified as statistical interpolation but differ mainly in how the forecast error covariances are modeled. Surface elevation and temperature data sampled from an 1/12° Gulf of Mexico HYCOM simulation designated as the truth are assimilated into an identical model starting from an erroneous initial state, and convergence of assimilative runs towards the truth is tracked. Sensitivity experiments are first performed to evaluate the impact of practical implementation choices such as the state vector structure, initialization procedures, correlation scales, covariance rank and details of handling multivariate datasets, and to identify an effective configuration for each assimilation method. The performance of the methods are then compared by examining the relative convergence of the assimilative runs towards the truth. All four methods show good skill and are able to enhance consistency between the assimilative and truth runs in both observed and unobserved model variables. Prediction errors in observed variables are typically less than the errors specified for the observations, and the differences between the assimilated products are small compared to the observation errors. For unobserved variables, RMS errors are reduced by 50% relative to a non-assimilative run and differ between schemes on average by about 5%. Dynamical consistency between the updated state space variables in the data assimilation algorithm, and the data adequately sampling significant dynamical features are the two crucial components for reliable predictions. The experiments presented here suggest that practical implementation details can have at least as much an impact on the accuracy of the assimilated product as the choice of assimilation technique itself. We also present a discussion of the numerical implementation and the computational requirements for the use of these methods in large scale applications

Correlates of functional disability in early rheumatoid arthritis: A cross-sectional study of 706 patients in four European countries

In this cross-sectional study of 706 European patients with rheumatoid arthritis (RA) of less than or equal to 4 yr duration, we examined possible correlates of functional disability assessed by the Health Assessment Questionnaire. First, we examined a subsample of 237 Norwegian patients. The Ritchie index: sex, age, erythrocyte sedimentation rate (ESR) and disease duration correlated significantly with disability, whereas serum rheumatoid factor, hand X-ray changes and educational level did not. Subsequently, we cross-validated these findings in a similar sample of 469 French, Dutch and Northern Irish patients. The results supported the Ritchie index, sex, ESR and disease duration as significant correlates of disability, whereas rheumatoid factor, age and education were not significantly correlated with disability. The correlation between X-ray changes and disability could not be cross-validated. The main findings of this study are that female sex correlates significantly with disability even early in the course of RA, whereas the rheumatoid factor does not