Analgesic consumption in a large sample of people in musculoskeletal rehabilitation: A descriptive study

BACKGROUND

Consumption of opioids is increasing worldwide in people with chronic non-cancer pain, although their effectiveness is debated.

OBJECTIVES

The aim of the current study was to evaluate analgesic consumption and its association with different variables (demographic variables, pain, anxiety/depression, catastrophism, and kinesiophobia), in the field of musculoskeletal rehabilitation, where no data are available.

METHODS

This was a retrospective study over a period of 8 years on people hospitalised for rehabilitation after injury. Participants were classified into 3 categories: no analgesics (NA), non-opioid analgesics (NOA), and opioid analgesics (OPA). ANOVA or chi-squared tests were used to compare the 3 groups.

RESULTS

A total of 4,350 people (84% men; mean [SD] age, 44 [11] years) were included. In total, 20% were taking OPA, 40% NOA and 40% NA. In the OPA group, tramadol was mainly used, and the morphine equivalent median dose was 8.3 mg/day. In the NOA group, paracetamol and ibuprofen were mostly used. Symptoms increased progressively across the 3 groups (NA/NOA/OPA), with increased levels of pain severity/interference, anxiety/depression and catastrophizing, and a higher prevalence of neuropathic pain in the OPA group versus the others.

CONCLUSIONS

These results are consistent with those found in groups of people with chronic pain taking larger doses of opioids and following opioid reduction or cessation programs. Opioid prescription did not increase over the 8 years, which was reassuring. These factors are important to emphasise because they can be modified in the rehabilitation setting with interdisciplinary management.

REGISTRATION

Our database was registered on Mendeley Data.

Should we separately measure the pain parameter of the Constant-Murley score in patients with chronic shoulder pain?

BACKGROUND

The Constant-Murley Score (CMS) is a relatively unique shoulder assessment tool because it combines patient-reported outcomes (pain and activity), performance measurement and clinician-reported outcomes (strength and mobility). With these characteristics, the effect of patient-related psychological factors on the CMS remains debated. We aimed to investigate which parameters of the CMS are influenced by psychological factors by assessing the CMS before and after rehabilitation for chronic shoulder pain.

METHODS

This retrospective study screened all patients (18-65 years old) who were admitted for interdisciplinary rehabilitation for chronic shoulder pain (≥ 3 months) between May 2012 and December 2017. Patients with unilateral shoulder injuries were eligible. Exclusion criteria were shoulder instability, concomitant neurological injuries, complex regional pain syndrome (including Steinbrocker syndrome), heavy psychiatric issues, and missing data. The Hospital Anxiety and Depression Scale, Pain Catastrophizing scale, and Tampa Scale of Kinesiophobia were administered before and after treatment. Regression models were used to estimate associations between psychological factors and the CMS.

RESULTS

We included 433 patients (88% male, mean age 47±11 years) with a median duration of symptoms of 392.2 days (interquartile range: 266.5-583.5). Rotator cuff issue was present in 71% of patients. During interdisciplinary rehabilitation, patients were followed for a mean of 33.6±7.5 days. The mean CMS at entry was 42.8 ±15.5. The mean gain in CMS after treatment was 10.6 ±10.9. Before treatment, psychological factors were significantly associated with only the pain CMS parameter: -0.37 (95% CI: -0.46 to -0.28), p <0.001. After treatment, psychological factors were associated with the evolution of the four CMS parameters: -0.12 (-0.23 to -0.01) to -0.26 (95% CI: -0.36 to -0.16), p<0.05.

CONCLUSIONS

This study raises the question of a distinct assessment of pain when assessing shoulder function with CMS in patients with chronic shoulder pain. The separation of the "pain parameter" from the overall CMS score seems illusory with this tool that is used worldwide. However, clinicians should be aware that psychological factors can negatively influence the evolution of all CMS parameters during follow-up, which argues for a biopsychosocial approach to patients with chronic shoulder pain.

Simple clinical tools improve ability-to-work predictions for individuals 3-24 months after upper limb injury

BACKGROUND

Despite numerous previous studies, predicting the ability to work (ATW) after an upper limb injury (ULI) remains difficult for those still not working 3-24 months after their initial injury.

OBJECTIVES

We aimed to identify simple prognostic characteristics that were associated with the long-term ATW for individuals who remained unable to work several months after the accident that caused their ULI.

METHODS

A single-center prospective observational study in a rehabilitation center in the French-speaking part of Switzerland. We included participants who were 18-60 years old, still unable to work because of persistent pain/disability 3-24 months after an ULI, and who were referred to our rehabilitation center for a 1-month intensive interdisciplinary treatment. Data were collected on personal characteristics, body function/structure variables, activity limitations/participation restrictions, and environmental factors. Participants' evolution during rehabilitation was assessed using functional tests/questionnaires and the 7-level self-reported Patient's Global Impression of Change (PGIC) assessment at discharge. Participant outcomes after 1 year were categorized as either able (ATW>0%) or unable (ATW=0%) to work. The best prognostic characteristics were selected by logistic regression analysis.

RESULTS

Among the 317 participants, 202 (64%) had an ATW>0% at 1 year. A grip strength ≥16 kg (Jamar Hand Dynamometer score - affected side) and "(I) do not take pain medicine" were independent predictors. Overall, 96% (26/27) of participants with these 2 characteristics had an ATW>0% at 1 year. The simultaneous absence of these characteristics predicted an unfavorable prognosis in 50% (59/119) of participants. For those who also had a positive PGIC score then 100% (25/25) of participants with these 3 characteristics had an ATW>0%; for those without, only 42% (19/45) had an ATW>0%.

CONCLUSIONS

Grip strength (≥16 kg) and not taking pain medicine are favorable prognostic factors for an ATW after an ULI. Their absence is associated with a poor ATW prognosis for half of people with ULI and should alert caregivers to risk of long-term absenteeism ("red flags"). Including data from a PGIC further improves the ATW prediction. We recommend that these 3 criteria be systematically evaluated.

Effect of a four-week isocaloric ketogenic diet on physical performance at very high-altitude: a pilot study

BACKGROUND

A ketogenic diet (KD) reduces daily carbohydrates (CHOs) ingestion by replacing most calories with fat. KD is of increasing interest among athletes because it may increase their maximal oxygen uptake (VO₂max), the principal performance limitation at high-altitudes (1500-3500 m). We examined the tolerance of a 4-week isocaloric KD (ICKD) under simulated hypoxia and the possibility of evaluating ICKD performance benefits with a maximal graded exercise bike test under hypoxia and collected data on the effect of the diet on performance markers and arterial blood gases.

METHODS

In a randomised single-blind cross-over model, 6 recreational mountaineers (age 24-44 years) completed a 4-week ICKD followed or preceded by a 4-week usual mixed Western-style diet (UD). Performance parameters (VO₂max, lactate threshold [LT], peak power [P_peak]) and arterial blood gases (PaO₂, PaCO₂, pH, HCO₃^-) were measured at baseline under two conditions (normoxia and hypoxia) as well as after a 4-week UD and 4-week ICKD under the hypoxic condition.

RESULTS

We analysed data for all 6 participants (BMI 19.9-24.6 kg m^-2). Mean VO₂max in the normoxic condition was 44.6 ml kg^-1 min^-1. Hypoxia led to decreased performance in all participants. With the ICKD diet, median values for PaO₂ decreased by - 14.5% and VO₂max by + 7.3% and P_peak by + 4.7%.

CONCLUSION

All participants except one could complete the ICKD. VO₂max improved with the ICKD under the hypoxia condition. Therefore, an ICKD is an interesting alternative to CHOs dependency for endurance performance at high-altitudes, including high-altitude training and high-altitude races. Nevertheless, decreased PaO₂ with ICKD remains a significant limitation in very-high to extreme altitudes (> 3500 m). Trial registration Clinical trial registration Nr. NCT05603689 (Clinicaltrials.gov). Ethics approval CER-VD, trial Nr. 2020-00427, registered 18.08.2020-prospectively registered.

Development and Validation of Short Forms of the Pain Catastrophizing Scale (F-PCS-5) and Tampa Scale for Kinesiophobia (F-TSK-6) in Musculoskeletal Chronic Pain Patients

Purpose

Chronic pain is a complex phenomenon. Understanding its multiple dimensions requires the use of a combination of several patient-reported outcome measures (PROMs). However, completing multiple PROMs is time-consuming and can be a burden for patients. The objective of our study was to simultaneously reduce the French versions of the Pain Catastrophizing Scale (PCS) and Tampa Scale for Kinesiophobia (TSK) questionnaires to enable their use in an ambulatory and clinical settings.

Patients and Methods

We conducted a clinical study between May 2014 and August 2020 in our rehabilitation center. 1428 chronic musculoskeletal pain patients (CMSP) were included. The originality of our approach is that the reduction method included qualitative as well as quantitative analyses. The study was divided into two parts: 1) reduction of the questionnaires (n=1363) based on internal consistency (item-to-total correlation), principal component analysis (item loadings), Rasch analysis (infit/outfit), floor and ceiling effect (quantitative analyses) and expert judgment of items (qualitative analysis), and 2) validation of the reduced questionnaires (n=65), including test-retest reliability (intraclass correlation coefficient [ICC]), homogeneity (Cronbach α), criterion validity (Pearson correlation [r] with the long-version score), determination of the pathological cutoff and Minimal Clinically Important Difference (MCID). The two full-length questionnaires include 30 items in total.

Results

The reduction resulted in a 5-item PCS (score 0-20) and 6-item TSK (score 0-24). Psychometric properties of the reduced questionnaires were all acceptable as compared with other version (α=0.89 and 0.71, ICC=0.75 and 0.60, r=0.86 and 0.70, MCID=2 and 2 for PCS and TSK, respectively) while keeping the structure and coherence of the long versions.

Conclusion

The two reduced versions of the PCS and TSK can be used in CMSP patient. As their administration only requires a few minutes, they can be implemented in outpatient consultation as well as in clinical settings.

Prosthetic fitting associated with better survival at 5 years after above-knee amputation due to vascular insufficiency

BACKGROUND

Individuals requiring non-traumatic Gritti-Stokes amputation or mid-thigh amputation usually have multiple comorbidities that place them at high risk of mortality.

OBJECTIVE

To determine survival rate 5 years after Gritti-Stokes and mid-thigh amputation in individuals with vascular insufficiency and to identify the predictors of survival.

METHODS

We conducted a retrospective observational study including all individuals with vascular insufficiency who underwent amputation from September 2007 to December 2015 in our University Hospital. The indication for amputation was limb necrosis in 86% of cases, infection in 10%, and complications with the stump (discomfort, neuroma or scar dehiscence) in 4%. Medical records were analysed to determine factors and comorbidities. The date of death was retrieved from the national death registry at a minimum of 5 years after amputation. Cox proportional-hazard regression was used to estimate associations between factors and post-amputation survival with hazard ratios (HR) and 95% confidence intervals (CIs).

RESULTS

We included 126 people with vascular insufficiency (83 men), mean age was 70 years [20; 97]; eighty-nine participants (71%) died during the study period. Survival rate was 68% at 1 year, 48% at 3 years and 37% at 5 years. Survival was associated with prosthetic fitting (HR 0.306 [95% CI 0.180; 0.521], p<0.001) and length of stay (HR 0.992 [95% CI 0.987; 0.997], p = 0.003). Conversely, limb necrosis was associated with a lower survival rate (HR 3.801 [95% CI 1.615; 8.949], p = 0.002). In a secondary multivariable analysis, Gritti-Stokes amputation was the only factor positively associated with prosthetic fitting (odds ratio 7.407 [95% CI 2.439; 22.489], p<0.001).

CONCLUSIONS

The survival rate at 5 years after Gritti-Stokes and mid-thigh amputation in people with vascular insufficiency was 37%. Prosthetic fitting was independently associated with better survival, and Gritti-Stokes amputation was the only factor positively related to prosthetic fitting.

Healthcare Costs, Time to Fitness for Work, and Related Factors in Chronic Complex Regional Pain Syndrome: A Comparative and Longitudinal Study of 5-Year Follow-Up

Purpose

To assess and compare the healthcare costs, time to fitness for work (TFW) between chronic complex regional pain syndrome (CRPS) and non-CRPS; and identify factors associated with these outcomes in a comparative longitudinal study.

Patients and Methods

148 patients with chronic CRPS of the hand and 273 patients with chronic hand impairments but without CRPS (non-CRPS) were admitted at a Swiss rehabilitation clinic between 2007 and 2016. Healthcare costs and TFW were retrieved from insurance data over 5 years after the accident. Socio-demographic factors, biopsychosocial complexity measured by means of the INTERMED questionnaire, pain intensity and DASH disability scores were collected during rehabilitation. Generalized estimation equations and Cox proportional-hazards models were used to identify factors associated with outcomes.

Results

Healthcare costs were increased by 20% for the CRPS versus non-CRPS group (coefficient = 1.20, 95% CI = 1.08-1.35, p<0.001). The median TFW was longer for CRPS than non-CRPS patients (816 vs 672 days, p = 0.02). After adjusting for covariates, TFW did not differ between the two groups (hazard ratio = 0.94, 95% CI = 0.73-1.21, p=0.61). For CRPS patients, higher healthcare costs were associated with severe or moderate initial injury, high INTERMED or DASH disability scores. Longer TFW were associated with severe initial injury, low educational level, no work contract, and high INTERMED or DASH disability scores.

Conclusion

Overall, the healthcare costs were higher for CRPS than non-CRPS patients, but the TFW was comparable. We demonstrated also the significant associations of disability and biopsychosocial factors with the healthcare costs and TFW in CRPS patients.

Genome-Wide Epigenomic Analyses in Patients With Nociceptive and Neuropathic Chronic Pain Subtypes Reveals Alterations in Methylation of Genes Involved in the Neuro-Musculoskeletal System

Nociceptive pain involves the activation of nociceptors without damage to the nervous system, whereas neuropathic pain is related to an alteration in the central or peripheral nervous system. Chronic pain itself and the transition from acute to chronic pain may be epigenetically controlled. In this cross-sectional study, a genome-wide DNA methylation analysis was performed using the blood DNA reduced representation bisulfite sequencing (RRBS) technique. Three prospective cohorts including 20 healthy controls (CTL), 18 patients with chronic nociceptive pain (NOCI), and 19 patients with chronic neuropathic pain (NEURO) were compared at both the single CpG and differentially methylated region (DMR) levels. Genes with DMRs were seen in the NOCI and NEURO groups belonged to the neuro-musculoskeletal system and differed between NOCI and NEURO patients. Our results demonstrate that the epigenetic disturbances accompanying nociceptive pain are very different from those accompanying neuropathic pain. In the former, among others, the epigenetic disturbance observed would affect the function of the opioid analgesic system, whereas in the latter it would affect that of the GABAergic reward system. This study presents biological findings that help to characterize NOCI- and NEURO-affected pathways and opens the possibility of developing epigenetic diagnostic assays. PERSPECTIVE: Our results help to explain the various biological pathways modifications underlying the different clinical manifestations of nociceptive and neuropathic pains. Furthermore, the new targets identified in our study might help to discover more specific treatments for nociceptive or neuropathic pains.

Determination of Perceived Levels of Physical Work Demand Thresholds, and Reliability and Responsiveness of the Modified-Spinal Function Sort Questionnaire in a Multidisciplinary Occupational Rehabilitation Setting

PURPOSE

To determine the levels of perceived work demand capacity corresponding to the Modified Spinal Function Sort (M-SFS) score and precise reliability validity and responsiveness.

METHODS

This prospective validation study included patients with chronic musculoskeletal impairments who underwent multidisciplinary occupational rehabilitation. After determining the percentiles of the work demand thresholds corresponding to the spinal function sort (SFS), the percentiles were transposed to the M-SFS. Reliability was assessed using the intraclass correlation coefficient and limits of agreement. Correlations with other questionnaires and a lifting task were measured to assess validity. Responsiveness was determined using anchor- and distribution-based approaches.

RESULTS

288 patients were included. The following thresholds were obtained for the M-SFS: 0-43 points, minimal; 44-50, very light; 51-58, light; 59-64, light to medium; 65-70, medium; 71-76, heavy; and 77-80, very heavy. Reliability was confirmed. The correlation between the M-SFS and SFS scores was good at 0.89 (95% CI, 0.86-0.91) and moderate according to the PILE-test result of 0.60 (95% CI, 0.50-0.67). We could not calculate a valid anchor-based minimal clinically important difference. The standard error of measurement was 3.9 points, and the smallest detectable change was 10.8 points.

CONCLUSIONS

On the basis of the comparison of the M-SFS and SFS scores, the M-SFS score can be interpreted in relation to the levels of work demand. This study confirms the good reliability and validity of the M-SFS questionnaire in assessing perceived physical capacity. Further studies are needed to determine its responsiveness.

Development and validation of a short version of the French Hand Function Sort questionnaire in vocational rehabilitation

BACKGROUND

The Hand Function Sort (HFS) is a pictorial self-administered questionnaire with 62 items. It is a valid and reliable scale focused on the physical function of the upper limbs. It is used to predict the return to work.

OBJECTIVES

We aimed to develop and validate a short version of the French version of the HFS (HFS-F) to simplify its use in clinical practice.

METHODS

We included patients with upper-limb chronic pain hospitalised for vocational rehabilitation from 2012 to 2019. Vocational rehabilitation aims to improve the autonomy of patients to regain their previous working capacity. The 62 items of the HFS-F were analysed in terms of patient and expert assessments, floor/ceiling effect, item-to-total correlation, principal component analysis, and Rasch analysis. A short HFS-F was developed. Thereafter, we assessed its internal consistency, test-retest reliability, criterion validity with the full-length HFS-F, construct validity with different scales (Disabilities of the Arm, Shoulder, and Hand [DASH]; Brief Pain Inventory [BPI]; Hospital Anxiety and Depression [HAD]), standard error of measurement (SEM), and minimal detectable change (MDC).

RESULTS

Six experts were consulted, 34 patients were interviewed, and 629 questionnaires were analysed. Among the items, 25 were selected after the final round with the six experts. The internal consistency and test-retest reliability were excellent (Cronbach α=0.95, intraclass correlation coefficient=0.92, 95% confidence interval [95% CI] 0.87 to 0.95). The correlation coefficient between scores of the short and full-length HFS-F was 0.841 (95% CI: 0.752 to 0.897, P<10-4), and those between the short HFS-F score and the DASH, BPI, HAD-Anxiety, and HAD-Depression scores were -0.816 (95% CI: -0.714 to -0.881, P<10-4), -0.529 (95% CI: -0.338 to -0.674, P<10-4), -0.451 (95% CI: -0.244 to 0.614, P=0.0001), and -0.360 (95% CI: -0.140 to -0.542, P=0.0018), respectively. The SEM and MDC values were estimated at 6/100 and 17/100, respectively.

CONCLUSIONS

A short version of the HFS-F was developed and validated. We named this questionnaire the 25 HFS-F.

Psychiatric Comorbidity and Complex Regional Pain Syndrome Through the Lens of the Biopsychosocial Model: A Comparative Study

PURPOSE

To compare the prevalence of psychiatric comorbidity between patients with complex regional pain syndrome (CRPS) of the hand and non-CRPS patients and to assess the association between biopsychosocial (BPS) complexity profiles and psychiatric comorbidity in a comparative study.

PATIENTS AND METHODS

We included a total of 103 patients with CRPS of the hand and 290 patients with chronic hand impairments but without CRPS. Psychiatric comorbidities were diagnosed by a psychiatrist, and BPS complexity was measured by means of the INTERMED. The odds ratios (OR) of having psychiatric comorbidities according to BPS complexity were calculated with multiple logistic regression (adjusted for age, sex, and pain).

RESULTS

Prevalence of psychiatric comorbidity was 29% in CRPS patients, which was not significantly higher than in non-CRPS patients (21%, relative risk=1.38, 95% CI: 0.95 to 2.01 p=0.10). The median total scores of the INTERMED were the same in both groups (23 points). INTERMED total scores (0-60 points) were related to an increased risk of having psychiatric comorbidity in CRPS patients (OR=1.46; 95% CI: 1.23-1.73) and in non-CRPS patients (OR=1.21; 95% CI: 1.13-1.30). The four INTERMED subscales (biological, psychological, social, and health care) were correlated with a higher risk of having psychiatric comorbidity in both groups. The differences in the OR of having psychiatric comorbidity in relation to INTERMED total and subscale scores were not statistically different between the two groups.

CONCLUSION

The total scores, as well as all four dimensions of BPS complexity measured by the INTERMED, were associated with psychiatric comorbidity, with comparable magnitudes of association between the CRPS and non-CRPS groups. The INTERMED was useful in screening for psychological vulnerability in the two groups.

The self-assessment INTERMED predicts healthcare and social costs of orthopaedic trauma patients with persistent impairments

Objective:

To use the self-assessment INTERMED questionnaire to determine the relationship between biopsychosocial complexity and healthcare and social costs of patients after orthopaedic trauma.

Design:

Secondary prospective analysis based on the validation study cohort of the self-assessment INTERMED questionnaire.

Setting:

Inpatients orthopaedic rehabilitation with vocational aspects.

Subjects:

In total, 136 patients with chronic pain and impairments were included in this study: mean (SD) age, 42.6 (10.7) years; 116 men, with moderate pain intensity (51/100); suffering from upper (n = 55), lower-limb (n = 51) or spine (n = 30) pain after orthopaedic trauma; with minor or moderate injury severity (severe injury for 25).

Main measures:

Biopsychosocial complexity, assessed with the self-assessment INTERMED questionnaire, and other confounding variables collected prospectively during rehabilitation. Outcome measures (healthcare costs, loss of wage costs and time for fitness-to-work) were collected through insurance files after case settlements. Linear multiple regression models adjusted for age, gender, pain, trauma severity, education and employment contract were performed to measure the influence of biopsychosocial complexity on the three outcome variables.

Results:

High-cost patients were older (+3.6 years) and more anxious (9.0 vs 7.3 points at HADS-A), came later to rehabilitation (+105 days), and showed higher biopsychosocial complexity (+3.2 points). After adjustment, biopsychosocial complexity was significantly associated with healthcare (ß = 0.02; P = 0.003; exp^ß = 1.02) and social costs (ß = 0.03; P = 0.006, exp^ß = 1.03) and duration before fitness-to-work (ß = 0.04; P < 0.001, exp^ß = 1.04).

Conclusion:

Biopsychosocial complexity assessed with the self-assessment INTERMED questionnaire is associated with higher healthcare and social costs.

Altered BDNF Methylation in Patients with Chronic Musculoskeletal Pain and High Biopsychosocial Complexity

Purpose

The INTERMED instrument, which was developed to measure patient's biopsychosocial (BPS) complexity, represents a powerful diagnostic and therapeutic tool. Epigenetic changes are the interface between signals from the environment and genetic modifications, affecting gene expression, in particular, by DNA methylation of CpG dinucleotides in promotor regions of the corresponding genes. The brain-derived neurotrophic factor (BDNF) gene plays a crucial role in the central sensitization (CS) of pain. In this study, we hypothesized that chronic pain modifies the methylation levels of the BDNF gene in a manner that is interconnected with the BPS status.

Patients and Methods

Fifty-eight chronic musculoskeletal pain patients (CMSP) were enrolled in the study. DNA was extracted from blood samples, the methylation levels of 13 CpG sites in the BDNF promoter were measured by pyrosequencing, and association studies with various patient parameters and the INTERMED scores were performed.

Results

Interestingly, a negative correlation (-0.40) was found between the total INTERMED scores and the average CpG methylation values of the BDNF gene, but no correlation was observed with the severity of pain, degree of anxiety, depression, or kinesiophobia and catastrophism. Moreover, the association was independent of age, sex and level of comorbidities.

Conclusion

This result shows that CMSP, in association with its biopsychosocial context, epigenetically decreases the degree of methylation of the BDNF promoter and should therefore increase the level of BDNF transcription. It also suggests a role of the INTERMED tool to detect a relationship between the BPS complexity and the epigenetic control of a target gene. The possible upregulation of BDNF expression might be, at least in part, the signal for chronic pain-induced central sensitization (CS). This could partly explain why patients with a higher level of complexity feel more pain than those with lower complexity.

Cross-cultural adaptation and measurement properties of the French version of the Trinity Amputation and Prosthesis Experience Scales-Revised (TAPES-R)

BACKGROUND

The Trinity Amputation and Prosthesis Experience Scales-Revised (TAPES-R) is a self-administered questionnaire to measure multidimensional adjustment to a prosthetic limb. Our aim was to assess the validity and reliability of the French version of the TAPES-R (TAPES-R-F).

MATERIALS AND METHODS

The cross-cultural adaptation was performed according to the recommendations. Factor analysis and Rasch analysis were also performed to allow comparison with the original English version. Construct validity was assessed by measuring the correlations between TAPES-R-F subscores and quality of life, pain, body image satisfaction, anxiety and depression. Internal consistency was measured with Cronbach's α. The standard error of measurement, smallest detectable change, Bland and Altman limits of agreement, and intraclass correlation were the measures of agreement and reliability.

RESULTS

No major difficulties were encountered throughout the trans-cultural adaptation process. The final version of the TAPES-R-F was well accepted and understood by the patients. According to the factor analysis, the satisfaction scale should be treated as a one-dimensional construct when used by French-speaking people and should not be separated into two separate subscales, functional and aesthetic, as is the case in the original English version. Our study confirmed that there is a strong relationship between biopsychosocial factors and adjustment to amputation. Cronbach's α > 0.8 for all the subscales. Reliability was good to excellent for all the subscales (ICCs between 0.61 and 0.89). The smallest detectable changes were 0.7, 0.8, 1.3, 0.4, and 1.8 (general adjustment, social adjustment, adjustment to limitation, activity restriction, and global satisfaction with the prosthesis).

CONCLUSIONS

The TAPES-R-F is a valid and reliable instrument to assess multidimensional adjustment of French-speaking lower limb amputees. This questionnaire can be used for both clinical assessment and research purposes.

Differences in the miRNA signatures of chronic musculoskeletal pain patients from neuropathic or nociceptive origins

BACKGROUND

The quality of life for millions of people worldwide is affected by chronic pain. In addition to the effect of chronic pain on well-being, chronic pain has also been associated with poor health conditions and increased mortality. Due to its multifactorial origin, the classification of pain types remains challenging. MicroRNAs (miRNA) are small molecules that regulate gene expression. They are released into the bloodstream in a stable manner under normal and pathological conditions and have been described as potential biomarkers. In the present study, we aimed to investigate whether pain may induce an aberrant, specific dysregulation of miRNA expression, depending on the origin of the pain.

METHODS AND FINDINGS

To do so, we measured the expression changes of 184 circulating miRNAs (c-miRNAs) in the plasma samples of patients with different origins of chronic musculoskeletal pain. After statistical analyses, we identified seven c-miRNA candidates that were differentially expressed depending on the nociceptive or neuropathic origin of the pain. We then developed a two c-miRNA signature (hsa-miR-320a and hsa-miR-98-5p) that was able to correctly classify the pain type of 70% of the patients from the validation set.

CONCLUSIONS

In conclusion, circulating miRNAs are promising biomarkers to identify and characterize the chronic pain type and to further improve its clinical management.

Influencing walking behavior can increase the physical activity of patients with chronic pain hospitalized for multidisciplinary rehabilitation: an observational study

Background

Physical therapy and exercising are key components of biopsychosocial rehabilitation for chronic pain. Exercise helps reduce pain and improve physical functions. In addition, a high level of physical activity benefits quality of life and emotional well-being. However, the degree to which hospitalization for extensive rehabilitation effectively increases physical activity has not yet been studied. Therefore, we investigated the physical activity level and the walking behavior of inpatients with musculoskeletal pain. The objectives were 1) to compare physical activity level and walking with or without rehabilitation, 2) to evaluate whether pain site influences physical activity level, and 3) to measure the association between physical activity and pain-related interference with physical functioning.

Methods

During a rehabilitation stay, 272 inpatients with lower limb, spine, or upper limb pain wore an accelerometer over 1 week. We assessed the daily duration of the practice of moderate physical activity and walking. Weekend days, during which the participants went home (days off), were used as a reference for habitual activities. We also evaluated 93 patients before the hospitalization to validate the use of days off as a baseline. Pain interference was measured with the brief pain inventory questionnaire. Generalized linear mixed models analyzed the association between physical activity and walking levels, and 1) rehabilitation participation, 2) pain sites, and 3) pain interference.

Results

Weekend days during the stay have similar physical activity level as days measured before the stay (73 min / day at the clinic, versus 70 min / day at home). Rehabilitation days had significantly higher physical activity levels and walking durations than days off (+ 28 min [+ 37%] and + 32 min [+ 74%], respectively). Mixed models revealed 1) a negative association between physical activity and pain interference, and 2) no effect of pain sites. Overall, patients increased their physical activity level independently of reported pain interference.

Conclusions

Despite their painful condition, the inpatients were able to engage themselves in a higher level of physical activity via increased participation in walking activities. We conclude that walking incentives can be a valid solution to help patients with chronic pain be more physically active.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2561-9) contains supplementary material, which is available to authorized users.

"Minimal clinically important difference" estimates of 6 commonly-used performance tests in patients with chronic musculoskeletal pain completing a work-related multidisciplinary rehabilitation program

Background

Functional tests are widely used to measure performance in patients with chronic musculoskeletal pain. Our objective was to determine the Minimal Clinically Important Differences (MCID) for the 6-min walk test (6MWT), the Steep Ramp Test (SRT), the 1-min stair climbing test (1MSCT), the sit-to-stand test (STS), the Jamar dynamometer test (JAM) and the lumbar Progressive Isoinertial Lifting Evaluation (PILE) in chronic musculoskeletal pain patients.

Methods

A single-center prospective observational study was conducted in a rehabilitation center. Patients with upper-limb, lower-limb or neck/back lesions were included over a period of 21 months. We used the anchor-based method as a reference method, supplemented by the distribution-based and opinion-based approaches, to determine the MCIDs.

Results

838 chronic musculoskeletal pain patients were included. The estimation method and thelesion location had a significant influence on the results. MCIDs were estimated at +75m and +60m for the 6MWT (lower-limb and neck/back lesions, respectively), +18 steps for the 1MSCT (lower-limb and neck/back lesions) and +6kg for the JAM (upper limb lesions). The anchor-based method could not provide valid estimations for the three other scales, but distribution and opinion-based methods provided rough values of MCIDs for the SRT (+39w to +61w), the STS (-5 sec to -7 sec) and the PILE (+4kg to +7kg).

Conclusion

The above MCID estimations for the 6MWT, 1MSCT and JAM can be used in chronic musculoskeletal pain patients participating in vocational multidisciplinary rehabilitation programs or in therapeutic trials. The use of specific anchors might give better estimations of MCIDs for the three other scales in future research.

Cross-cultural adaptation and validation of the ABIS questionnaire for French speaking amputees

Background: The Amputee Body Image Scale (ABIS) and its shortened version (ABIS-R) are self-administered questionnaires to measure body image perception of amputee. Our aim was to assess the validity and reliability of the French ABIS (ABIS-F and ABIS-R-F).Methods: Ninety-nine patients were included. The cross-cultural adaptation was performed according to the recommendations. Construct validity was assessed by measuring the correlation between ABIS-F or ABIS-R-F scores and quality of life, pain, anxiety, and depression. Internal consistency was measured with Cronbach's α. The standard error of measurement, smallest detectable change, Bland and Altman limits of agreement, and intraclass correlation were the measures of agreement and reliability.Results: A highest body image disturbance was associated with lowest quality of life, higher pain, and higher anxiety, and depression. Cronbach's α was 0.91/0.89 (ABIS-F/ABIS-R-F). The standard error of measurement was 5.35/2.28 (ABIS-F/ABIS-R-F). The smallest detectable change was 14.82/6.31 (ABIS-F/ABIS-R-F). The mean difference in ABIS-F score was -3.90 with limits of agreement from -18.71 to 10.92. For ABIS-R-F, the mean difference was -2.12 with limits of agreement from -8.43 to 4.19. Intraclass correlation was 0.87/0.82 (ABIS-F/ABIS-R-F).Conclusions: The French versions ABIS-F and ABIS-R-F share similar psychometric properties, both are as reliable, but ABIS-R-F has a better response structure and is more feasible.Implications for rehabilitationThe quality of life of amputees is impacted by their satisfaction with body imageThe Amputee Body Image Scale questionnaire measures this perception and is available for French-speaking amputeesThe Standard Errors of Measurement proposed could be useful for clinical and research purposesBoth ABIS and ABIS-R showed satisfactory construct validity, internal consistency, and reliabilityThe shortened version has a better response structure and is more readily feasible.

Avoidance, pacing, or persistence in multidisciplinary functional rehabilitation for chronic musculoskeletal pain: An observational study with cross-sectional and longitudinal analyses

Background

Three main activity patterns have been distinguished in describing chronic pain (avoidance, pacing and persistence). However, their influence on patient outcomes remains a question of debate. This observational study aimed to measure the associations between the avoidance, pacing, and persistence (labelled overdoing) scales of the Patterns of Activity Measure–Pain (POAM-P), self-reported outcomes (pain-interference, depression, functional ability), and observational outcomes (walking, lifting test, physical fitness).

Methods

We conducted an observational study with cross-sectional and longitudinal analyses. The data were collected prospectively before and after treatment, which was a 5-week functional rehabilitation including vocational aspects. In addition to self-reported and observational outcomes, patients were asked if they thought they would be able to return to work at 6 months. Analyses were conducted with treatment effect sizes, correlations, and multiple regression models.

Results

In this sample (891 patients), we found on average small to moderate improvements for pain-interference and observational outcomes (Cohen’s d: 0.37 to 0.64). According to the multivariable models, overdoing was associated with most of the beneficial psychosocial and observational outcomes (β -0.13 to 0.17; all p<0.01). Avoidance was related to negative psychosocial outcomes before treatment (β -0.09 to 0.17; all p<0.015). Pacing, which had moderate correlation with avoidance (r = 0.46), was not associated with most of the outcomes. The feeling that the goal of returning to work was attainable was associated with lower avoidance scores (adjusted OR 0.97; p = 0.024).

Conclusions

The overdoing POAM-P scale probably measures a task-contingent persistence, which appears appropriate in the setting of this study. Persistent behavior was indeed related to small or moderate positive biopsychosocial outcomes, before and after treatment. Moreover feeling able to return to work was related to lower avoidance. Further studies should test the efficacy of motivational strategies that may promote functional task-contingent persistence and reduce avoidance of painful tasks.

Predictive Value of the Fear-Avoidance Model on Functional Capacity Evaluation

Purpose Measuring the predictive value of the Fear-Avoidance Model (FAM) on lifting tasks in Functional Capacity Evaluation (FCE), and on reasons for stopping the evaluation (safe maximal effort, versus self-limited). Methods A monocentric prospective study was conducted on 298 consecutive inpatients. Components of the FAM were analyzed using the Cumulative Psychosocial Factor Index (CPFI: kinesiophobia, catastrophizing, depressive mood) and perceived disability (Hand/Spinal Function Sort: HFS/SFS). Floor-to-waist, waist-to-overhead and dominant-hand lifting tests were measured according to the FCE guidelines. Maximal safe performance was judged by certified FCE assessors. Analyses were conducted with linear multiple regression models. Results The CPFI was significantly associated with the 3 FCE lifting tests: floor-to-waist (ß = - 1.12; p = 0.039), waist-to-overhead (ß = - 0.88; p = 0.011), and dominant-handed lifting (ß = - 1.21; p = 0.027). Higher perceived disability was also related to lower performances: floor-to-waist (ß = 0.09; p < 0.001), waist-to-overhead (ß = 0.04; p < 0.001), and dominant-handed lifting (ß = 0.06; p < 0.001). The CPFI was not related to performances of patients with self-limited effort despite higher psychological scores, while a relationship was found for patients who achieved a safe maximal performance. Higher perceived disability was related to performances in both situations. Conclusions FAM components should be taken into account when interpreting maximal physical performance in FCE. This study also suggests that factors other than pain-related fears may influence patients with self-limited effort.

Immediate and short-term effects of kinesiotaping on muscular activity, mobility, strength and pain after rotator cuff surgery: a crossover clinical trial

BACKGROUND

Kinesiotape (KT) is widely used in musculoskeletal rehabilitation as an adjuvant to treatment, but minimal evidence supports its use. The aim of this study is to determine the immediate and short-term effects of shoulder KT on muscular activity, mobility, strength and pain after rotator cuff surgery.

METHODS

Thirty-nine subjects who underwent shoulder rotator cuff surgery were tested 6 and 12 weeks post-surgery, without tape, with KT and with a sham tape (ST). KT and ST were applied in a randomized order. For each condition, the muscular activity of the upper trapezius, three parts of the deltoid and the infraspinatus were measured during shoulder flexion, and range of motion (ROM) and pain intensity were assessed. At 12 weeks, the isometric strength at 90° of shoulder flexion, related muscular activity and pain intensity were also measured. Subjects maintained the last tape that was applied for three days and recorded the pain intensity at waking up and during the day.

RESULTS

Modifications in muscle activity were observed with KT and with ST. Major changes in terms of decreased recruitment of the upper trapezius were observed with KT (P < 0.001). KT and ST also increased flexion ROM at 6 weeks (P = 0.004), but the differences with the no tape condition were insufficient to be clinically important. No other differences between conditions were found.

CONCLUSIONS

Shoulder taping has the potential to decrease over-activity of the upper trapezius, but no clinical benefits of KT on ROM, strength or pain were noted in a population of subjects who underwent rotator cuff surgery.

TRIAL REGISTRATION

The study was retrospectively registered on ClinicalTrials.gov PRS ( NCT03379636 ) on 21st December 2017.

Working Together and Being Physically Active Are Not Enough to Advise Uniformly and Adequately Low Back Pain Patients: A Cross-Sectional Study

The profession of the health-care providers (HCPs) influences their recommendations to the patients. Conversely, interdisciplinarity seeks to challenge such differences, so that the patient receives one single and consistent therapeutic message. Some studies also suggest associations between HCPs life habits and recommendations. Our hypotheses were (1) that despite interdisciplinary work, the profession remains a predictor of recommendations and (2) that HCPs who are more physically active recommend more activity. Three clinical vignettes were presented to a group of experts of low back pain (LBP) (guidelines), and 20 physicians, 22 physiotherapists, and 23 nurses to assess how they evaluate the symptoms and pathologies of LBP patients and how much work and physical activity they recommend. Physical activity was assessed with accelerometers and questionnaires. Some interprofessional differences remained present within an interdisciplinary team. The nurses were more restrictive and further away from the guidelines. The physicians were the most in line with them. The physiotherapists recommend as much physical activity, but less work activity than the physicians. The level of physical activity of the HCPs is not associated with their recommendations. To ensure a clear and unique message, educational actions may be undertaken to promote the biopsychosocial model and clarify the guidelines.

A Return-to-Work Prognostic Model for Orthopaedic Trauma Patients (WORRK) Updated for Use at 3, 12 and 24 Months

Purpose Updating the Wallis Occupational Rehabilitation Risk (WORRK) model formula, predicting non-return to work (nRTW) at different time points (3 and 12 months) than in the validation study (2 years). Methods Secondary analysis of two samples was carried out (following orthopaedic trauma), including work status, the first at 3 months (428 patients) and the second at 12 months (431 patients) after discharge from rehabilitation. We used calibration (agreement between predicted probabilities and observed frequencies) and discrimination (area under the receiver operating characteristics curve) to assess performance of the model after fitting it in the new sample, then calculated the probabilities of nRTW based on the coefficients from the 2-year prediction. Finally, the intercepts were updated for both 3- and 12-month prediction models (re-calibration was necessary for the adjustment of these probabilities) and performance re-evaluated. Results Patient characteristics were similar in all samples (mean age 43 in both groups; 86% male at 3 months, 84% male at 12 months). The proportion of nRTW at 3 months was 63.8% and 53.4% at 12 months (50.36% at 2 years). Performance of the original WORRK for both 3- and 12-month prediction showed an AUC of 0.73, while statistically significant miscalibration was found for both time points (p < 0.001). After the updating of the intercept, calibration was improved and did not show significant miscalibration (p = 0.458 and 0.341). The AUC stayed at 0.73. Conclusion The WORRK model was successfully adapted by changing the intercept for 3- and 12-month prediction of nRTW, now available for use in clinical practice.

Adapting the "Chester step test" to predict peak oxygen uptake in children

AIM OF THE STUDY

Maximal exercise testing may be difficult to perform in clinical practice, especially in obese children who have low cardiorespiratory fitness and exercise tolerance. We aimed to elaborate a model predicting peak oxygen consumption (VO2) in lean and obese children with use of the submaximal Chester step test.

METHODS

We performed a maximal step test, which consisted of 2-minute stages with increasing intensity to exhaustion, in 169 lean and obese children (age range: 7-16 years). VO2 was measured with indirect calorimetry. A statistical Tobit model was used to predict VO2 from age, gender, body mass index (BMI) z-score and intensity levels. Estimated VO2peak was then determined from the heart rate-VO2 linear relationship extrapolated to maximal heart rate (220 minus age, in beats.min-1).

RESULTS

VO2 (ml/kg/min) can be predicted using the following equation: VO2 = 22.82 - [0.68*BMI z-score] - [0.46*age (years)] - [0.93*gender (male = 0; female = 1)] + [4.07*intensity level (stage 1, 2, 3 etc.)] - [0.24*BMI z-score *intensity level] - [0.34*gender*intensity level]. VO2 was lower in participants with high BMI z-scores and in female subjects.

CONCLUSION

The Chester step test can assess cardiorespiratory fitness in lean and obese children in clinical settings. Our adapted equation allows the Chester step test to be used to estimate peak aerobic capacity in children.

Optimal slopes and speeds in uphill ski mountaineering: a field study

PURPOSE

The aim of this study is to describe the effects of speed and gradient during uphill ski mountaineering on energy expenditure, to relate any changes to changes in stride characteristics, and to determine an optimal gradient and speed allowing minimization of energy expenditure.

METHODS

11 subjects were tested on snowy trails using their mountaineering skis (fitted with skins), boots and poles, at three gradients (7, 11 and 33 %) at 80 % of maximum heart rate (HRmax), and at 11 % also at 90 and 100 % of HRmax. Energy expenditure was calculated by indirect calorimetry to derive energy cost of locomotion (EC), vertical energy cost (ECvert) and mechanical efficiency, while stride length, stride frequency, relative and absolute thrust phase duration, and slope gradient were measured with an inertial sensor-based system.

RESULTS

At 11 % there was no change with speed in EC, ECvert and mechanical efficiency, while stride length and frequency increased and absolute thrust phase duration decreased. There was an effect of gradient on EC, ECvert and mechanical efficiency, while speed, stride length and stride frequency decreased and absolute and relative thrust phase duration increased. The most economical gradient (lowest ECvert) was the steepest one.

CONCLUSION

During ski mountaineering uphill at shallow gradient (11 %), EC, ECvert and mechanical efficiency do not vary with speed, while at steeper gradient (33 %) economy is improved. It follows that to minimize energy expenditure and optimize performance to reach a place located at a higher altitude, an athlete should choose a steep gradient, if he/she is able to maintain a sufficient speed.

CYP17A1 Enzyme Activity Is Linked to Ambulatory Blood Pressure in a Family-Based Population Study

BACKGROUND

Genome-wide association studies have linked CYP17A1 coding for the steroid hormone synthesizing enzyme 17α-hydroxylase (CYP17A1) to blood pressure (BP). We hypothesized that the genetic signal may translate into a correlation of ambulatory BP (ABP) with apparent CYP17A1 activity in a family-based population study and estimated the heritability of CYP17A1 activity.

METHODS

In the Swiss Kidney Project on Genes in Hypertension, day and night urinary excretions of steroid hormone metabolites were measured in 518 participants (220 men, 298 women), randomly selected from the general population. CYP17A1 activity was assessed by 2 ratios of urinary steroid metabolites: one estimating the combined 17α-hydroxylase/17,20-lyase activity (ratio 1) and the other predominantly 17α-hydroxylase activity (ratio 2). A mixed linear model was used to investigate the association of ABP with log-transformed CYP17A1 activities exploring effect modification by urinary sodium excretion.

RESULTS

Daytime ABP was positively associated with ratio 1 under conditions of high, but not low urinary sodium excretion (P interaction <0.05). Ratio 2 was not associated with ABP. Heritability estimates (SE) for day and night CYP17A1 activities were 0.39 (0.10) and 0.40 (0.09) for ratio 1, and 0.71 (0.09) and 0.55 (0.09) for ratio 2 (P values <0.001). CYP17A1 activities, assessed with ratio 1, were lower in older participants.

CONCLUSIONS

Low apparent CYP17A1 activity (assessed with ratio 1) is associated with elevated daytime ABP when salt intake is high. CYP17A1 activity is heritable and diminished in the elderly. These observations highlight the modifying effect of salt intake on the association of CYP17A1 with BP.

Optimal slopes and speeds in uphill ski mountaineering: a laboratory study

PURPOSE

The purpose of this study was to estimate the energy cost of linear (EC) and vertical displacement (ECvert), mechanical efficiency and main stride parameters during simulated ski mountaineering at different speeds and gradients, to identify an optimal speed and gradient that maximizes performance.

METHODS

12 subjects roller skied on a treadmill at three different inclines (10, 17 and 24 %) at three different speeds (approximately 70, 80 and 85 % of estimated peak heart rate). Energy expenditure was calculated by indirect calorimetry, while biomechanical parameters were measured with an inertial sensor-based system.

RESULTS

At 10 % there was no significant change with speed in EC, ECvert and mechanical efficiency. At 17 and 24 % the fastest speed was significantly more economical. There was a significant effect of gradient on EC, ECvert and mechanical efficiency. The most economical gradient was the steepest one. There was a significant increase of stride frequency with speed. At steep gradients only, relative thrust phase duration decreased significantly, while stride length increased significantly with speed. There was a significant effect of gradient on stride length (decrease with steepness) and relative thrust phase duration (increase with steepness).

CONCLUSION

A combination of a decreased relative thrust phase duration with increased stride length and frequency decreases ECvert. To minimize the energy expenditure to reach the top of a mountain and to optimize performance, ski-mountaineers should choose a steep gradient (~24 %) and, provided they possess sufficient metabolic scope, combine it with a fast speed (~6 km h(-1)).

Subjective perceptions as prognostic factors of time to fitness for work during a 4-year period after inpatient rehabilitation for orthopaedic trauma

INTRODUCTION

Time to fitness for work (TFW) was measured as the number of days that were paid as compensation for work disability during the 4 years after discharge from the rehabilitation clinic in a population of patients hospitalised for rehabilitation after orthopaedic trauma. The aim of this study was to test whether some psychological variables can be used as potential early prognostic factors of TFW.

MATERIAL AND METHODS

A Cox proportional hazards model was used to estimate the associations between predictive variables and TFW. Predictors were global health, pain at hospitalisation and pain decrease during the stay (all continuous and standardised by subtracting the mean and dividing by two standard deviations), perceived severity of the trauma and expectation of a positive evolution (both binary variables).

RESULTS

Full data were available for 807 inpatients (660 men, 147 women). TFW was positively associated with better perceived health (hazard ratio [HR] 1.16, 95% confidence interval [CI] 1.13-1.19), pain decrease (HR 1.46, 95% CI 1.30-1.64) and expectation of a positive evolution (HR 1.50, 95% CI 1.32-1.70) and negatively associated with pain at hospitalisation (HR 0.67, 95% CI 0.59-0.76) and high perceived severity (HR 0.72, 95% CI 0.61-0.85).

DISCUSSION

The present results provide some evidence that work disability during a four-year period after rehabilitation may be predicted by prerehabilitation perceptions of general health, pain, injury severity, as well as positive expectation of evolution.

Associations of Ambulatory Blood Pressure With Urinary Caffeine and Caffeine Metabolite Excretions

Intake of caffeinated beverages might be associated with reduced cardiovascular mortality possibly via the lowering of blood pressure. We estimated the association of ambulatory blood pressure with urinary caffeine and caffeine metabolites in a population-based sample. Families were randomly selected from the general population of Swiss cities. Ambulatory blood pressure monitoring was conducted using validated devices. Urinary caffeine, paraxanthine, theophylline, and theobromine excretions were measured in 24 hours urine using ultrahigh performance liquid chromatography tandem mass spectrometry. We used mixed models to explore the associations of urinary excretions with blood pressure although adjusting for major confounders. The 836 participants (48.9% men) included in this analysis had mean age of 47.8 and mean 24-hour systolic and diastolic blood pressure of 120.1 and 78.0 mm Hg. For each doubling of caffeine excretion, 24-hour and night-time systolic blood pressure decreased by 0.642 and 1.107 mm Hg (both P values <0.040). Similar inverse associations were observed for paraxanthine and theophylline. Adjusted night-time systolic blood pressure in the first (lowest), second, third, and fourth (highest) quartile of paraxanthine urinary excretions were 110.3, 107.3, 107.3, and 105.1 mm Hg, respectively ( P trend <0.05). No associations of urinary excretions with diastolic blood pressure were generally found, and theobromine excretion was not associated with blood pressure. Anti-hypertensive therapy, diabetes mellitus, and alcohol consumption modify the association of caffeine urinary excretion with systolic blood pressure. Ambulatory systolic blood pressure was inversely associated with urinary excretions of caffeine and other caffeine metabolites. Our results are compatible with a potential protective effect of caffeine on blood pressure.

New anthropometry-based age- and sex-specific reference values for urinary 24-hour creatinine excretion based on the adult Swiss population

BACKGROUND

Urinary creatinine excretion is used as a marker of completeness of timed urine collections, which are a keystone of several metabolic evaluations in clinical investigations and epidemiological surveys.

METHODS

We used data from two independent Swiss cross-sectional population-based studies with standardised 24-hour urinary collection and measured anthropometric variables. Only data from adults of European descent, with estimated glomerular filtration rate (eGFR) ≥60 ml/min/1.73 m2 and reported completeness of the urinary collection were retained. A linear regression model was developed to predict centiles of the 24-hour urinary creatinine excretion in 1,137 participants from the Swiss Survey on Salt and validated in 994 participants from the Swiss Kidney Project on Genes in Hypertension.

RESULTS

The mean urinary creatinine excretion was 193 ± 41 μmol/kg/24 hours in men and 151 ± 38 μmol/kg/24 hours in women in the Swiss Survey on Salt. The values were inversely correlated with age and body mass index (BMI).

CONCLUSIONS

We propose a validated prediction equation for 24-hour urinary creatinine excretion in the general European population, based on readily available variables such as age, sex and BMI, and a few derived normograms to ease its clinical application. This should help healthcare providers to interpret the completeness of a 24-hour urine collection in daily clinical practice and in epidemiological population studies.

Copeptin is associated with kidney length, renal function, and prevalence of simple cysts in a population-based study

Arginine vasopressin (AVP) has a key role in osmoregulation by facilitating water transport in the collecting duct. Recent evidence suggests that AVP may have additional effects on renal function and favor cyst growth in polycystic kidney disease. Whether AVP also affects kidney structure in the general population is unknown. We analyzed the association of copeptin, an established surrogate for AVP, with parameters of renal function and morphology in a multicentric population-based cohort. Participants from families of European ancestry were randomly selected in three Swiss cities. We used linear multilevel regression analysis to explore the association of copeptin with renal function parameters as well as kidney length and the presence of simple renal cysts assessed by ultrasound examination. Copeptin levels were log-transformed. The 529 women and 481 men had median copeptin levels of 3.0 and 5.2 pmol/L, respectively (P<0.001). In multivariable analyses, the copeptin level was associated inversely with eGFR (β=-2.1; 95% confidence interval [95% CI], -3.3 to -0.8; P=0.002) and kidney length (β=-1.2; 95% CI, -1.9 to -0.4; P=0.003) but positively with 24-hour urinary albumin excretion (β=0.11; 95% CI, 0.01 to 0.20; P=0.03) and urine osmolality (β=0.08; 95% CI, 0.05 to 0.10; P<0.001). A positive association was found between the copeptin level and the presence of renal cysts (odds ratio, 1.6; 95% CI, 1.1 to 2.4; P=0.02). These results suggest that AVP has a pleiotropic role in renal function and may favor the development of simple renal cysts.

Epidemiology of masked and white-coat hypertension: the family-based SKIPOGH study

Objective

We investigated factors associated with masked and white-coat hypertension in a Swiss population-based sample.

Methods

The Swiss Kidney Project on Genes in Hypertension is a family-based cross-sectional study. Office and 24-hour ambulatory blood pressure were measured using validated devices. Masked hypertension was defined as office blood pressure<140/90 mmHg and daytime ambulatory blood pressure≥135/85 mmHg. White-coat hypertension was defined as office blood pressure≥140/90 mmHg and daytime ambulatory blood pressure<135/85 mmHg. Mixed-effect logistic regression was used to examine the relationship of masked and white-coat hypertension with associated factors, while taking familial correlations into account. High-normal office blood pressure was defined as systolic/diastolic blood pressure within the 130–139/85–89 mmHg range.

Results

Among the 652 participants included in this analysis, 51% were female. Mean age (±SD) was 48 (±18) years. The proportion of participants with masked and white coat hypertension was respectively 15.8% and 2.6%. Masked hypertension was associated with age (odds ratio (OR) = 1.02, p = 0.012), high-normal office blood pressure (OR = 6.68, p<0.001), and obesity (OR = 3.63, p = 0.001). White-coat hypertension was significantly associated with age (OR = 1.07, p<0.001) but not with education, family history of hypertension, or physical activity.

Conclusions

Our findings suggest that physicians should consider ambulatory blood pressure monitoring for older individuals with high-normal office blood pressure and/or who are obese.

Reference Values and Factors Associated With Renal Resistive Index in a Family-Based Population Study

Increased renal resistive index (RRI) has been recently associated with target organ damage and cardiovascular or renal outcomes in patients with hypertension and diabetes mellitus. However, reference values in the general population and information on familial aggregation are largely lacking. We determined the distribution of RRI, associated factors, and heritability in a population-based study. Families of European ancestry were randomly selected in 3 Swiss cities. Anthropometric parameters and cardiovascular risk factors were assessed. A renal Doppler ultrasound was performed, and RRI was measured in 3 segmental arteries of both kidneys. We used multilevel linear regression analysis to explore the factors associated with RRI, adjusting for center and family relationships. Sex-specific reference values for RRI were generated according to age. Heritability was estimated by variance components using the ASSOC program (SAGE software). Four hundred women (mean age±SD, 44.9±16.7 years) and 326 men (42.1±16.8 years) with normal renal ultrasound had mean RRI of 0.64±0.05 and 0.62±0.05, respectively ( P <0.001). In multivariable analyses, RRI was positively associated with female sex, age, systolic blood pressure, and body mass index. We observed an inverse correlation with diastolic blood pressure and heart rate. Age had a nonlinear association with RRI. We found no independent association of RRI with diabetes mellitus, hypertension treatment, smoking, cholesterol levels, or estimated glomerular filtration rate. The adjusted heritability estimate was 42±8% ( P <0.001). In a population-based sample with normal renal ultrasound, RRI normal values depend on sex, age, blood pressure, heart rate, and body mass index. The significant heritability of RRI suggests that genes influence this phenotype.

Reticulocyte dynamic and hemoglobin variability in hemodialysis patients treated with Darbepoetin alfa and C.E.R.A.: a randomized controlled trial

Background

In a simulation based on a pharmacokinetic model we demonstrated that increasing the erythropoiesis stimulating agents (ESAs) half-life or shortening their administration interval decreases hemoglobin variability. The benefit of reducing the administration interval was however lessened by the variability induced by more frequent dosage adjustments. The purpose of this study was to analyze the reticulocyte and hemoglobin kinetics and variability under different ESAs and administration intervals in a collective of chronic hemodialysis patients.

Methods

The study was designed as an open-label, randomized, four-period cross-over investigation, including 30 patients under chronic hemodialysis at the regional hospital of Locarno (Switzerland) in February 2010 and lasting 2 years. Four subcutaneous treatment strategies (C.E.R.A. every 4 weeks Q4W and every 2 weeks Q2W, Darbepoetin alfa Q4W and Q2W) were compared with each other. The mean square successive difference of hemoglobin, reticulocyte count and ESAs dose was used to quantify variability. We distinguished a short- and a long-term variability based respectively on the weekly and monthly successive difference.

Results

No difference was found in the mean values of biological parameters (hemoglobin, reticulocytes, and ferritin) between the 4 strategies. ESAs type did not affect hemoglobin and reticulocyte variability, but C.E.R.A induced a more sustained reticulocytes response over time and increased the risk of hemoglobin overshooting (OR 2.7, p = 0.01). Shortening the administration interval lessened the amplitude of reticulocyte count fluctuations but resulted in more frequent ESAs dose adjustments and in amplified reticulocyte and hemoglobin variability. Q2W administration interval was however more favorable in terms of ESAs dose, allowing a 38% C.E.R.A. dose reduction, and no increase of Darbepoetin alfa.

Conclusions

The reticulocyte dynamic was a more sensitive marker of time instability of the hemoglobin response under ESAs therapy. The ESAs administration interval had a greater impact on hemoglobin variability than the ESAs type. The more protracted reticulocyte response induced by C.E.R.A. could explain both, the observed higher risk of overshoot and the significant increase in efficacy when shortening its administration interval.

Trial registration

ClinicalTrials.gov: NCT01666301

Serum uric acid and adiposity: deciphering causality using a bidirectional Mendelian randomization approach

Background

Although the relationship between serum uric acid (SUA) and adiposity is well established, the direction of the causality is still unclear in the presence of conflicting evidences. We used a bidirectional Mendelian randomization approach to explore the nature and direction of causality between SUA and adiposity in a population-based study of Caucasians aged 35 to 75 years.

Methods and Findings

We used, as instrumental variables, rs6855911 within the SUA gene SLC2A9 in one direction, and combinations of SNPs within the adiposity genes FTO, MC4R and TMEM18 in the other direction. Adiposity markers included weight, body mass index, waist circumference and fat mass. We applied a two-stage least squares regression: a regression of SUA/adiposity markers on our instruments in the first stage and a regression of the response of interest on the fitted values from the first stage regression in the second stage. SUA explained by the SLC2A9 instrument was not associated to fat mass (regression coefficient [95% confidence interval]: 0.05 [−0.10, 0.19] for fat mass) contrasting with the ordinary least square estimate (0.37 [0.34, 0.40]). By contrast, fat mass explained by genetic variants of the FTO, MC4R and TMEM18 genes was positively and significantly associated to SUA (0.31 [0.01, 0.62]), similar to the ordinary least square estimate (0.27 [0.25, 0.29]). Results were similar for the other adiposity markers.

Conclusions

Using a bidirectional Mendelian randomization approach in adult Caucasians, our findings suggest that elevated SUA is a consequence rather than a cause of adiposity.

A comparison of three methods of Mendelian randomization when the genetic instrument, the risk factor and the outcome are all binary

The method of instrumental variable (referred to as Mendelian randomization when the instrument is a genetic variant) has been initially developed to infer on a causal effect of a risk factor on some outcome of interest in a linear model. Adapting this method to nonlinear models, however, is known to be problematic. In this paper, we consider the simple case when the genetic instrument, the risk factor, and the outcome are all binary. We compare via simulations the usual two-stages estimate of a causal odds-ratio and its adjusted version with a recently proposed estimate in the context of a clinical trial with noncompliance. In contrast to the former two, we confirm that the latter is (under some conditions) a valid estimate of a causal odds-ratio defined in the subpopulation of compliers, and we propose its use in the context of Mendelian randomization. By analogy with a clinical trial with noncompliance, compliers are those individuals for whom the presence/absence of the risk factor X is determined by the presence/absence of the genetic variant Z (i.e., for whom we would observe X = Z whatever the alleles randomly received at conception). We also recall and illustrate the huge variability of instrumental variable estimates when the instrument is weak (i.e., with a low percentage of compliers, as is typically the case with genetic instruments for which this proportion is frequently smaller than 10%) where the inter-quartile range of our simulated estimates was up to 18 times higher compared to a conventional (e.g., intention-to-treat) approach. We thus conclude that the need to find stronger instruments is probably as important as the need to develop a methodology allowing to consistently estimate a causal odds-ratio.