A Rasch Analysis of the Charcot-Marie-Tooth Neuropathy Score (CMTNS) in a Cohort of Charcot-Marie-Tooth Type 1A Patients

The Patient Activation Measure-13 (PAM-13) in an oncology patient population: psychometric properties and dimensionality evaluation

BACKGROUND

Accurate assessment and enhancement of health-related skills among oncology patients are pivotal for optimizing cancer care. The Patient Activation Measure (PAM-13), a questionnaire designed to reflect an individual's knowledge, skills, and confidence in self-healthcare management, has been validated across diverse countries and settings. Concerns have been raised regarding the cross-situational applicability, as patients with specific diseases and cultural backgrounds interpret questionnaire items differently. This study aimed to examine the structural validity and psychometric properties of the PAM-13 in an oncological patient cohort.

METHODS

Baseline data from a longitudinal non-randomized controlled study involving cancer out-patients (n = 1,125) from Comprehensive Cancer Centres in Southern Germany were analysed. The German version of the PAM-13 was employed. With classical test and item response theory methods data quality, reliability, convergent and structural validity, as well as psychometric properties were assessed. Exploratory (EFA) and confirmatory factor analyses (CFA) were employed to investigate the postulated unidimensionality of the underlying construct. With a partial credit model (PCM) we examined item fit, targeting, local independence and differential item functioning.

RESULTS

Participants were predominantly female (73.0%) with a breast cancer diagnosis (41.3%). While items were generally well-accepted, ceiling effects were observed and a high mean PAM-13 score (69.7, SD = 14.2) was noted, potentially compromising responsiveness to interventions. Reliability was adequate (Cronbach's α = 0.81), person and item separation reliability were good to excellent (0.81 and 0.99, respectively). Explorations of the unidimensionality of the construct (EFA, CFA, PCM) yielded inconclusive results, hinting towards a two-factor solution. Item difficulty rankings deviated from the original. No differential item functioning was identified, and local independence was confirmed.

CONCLUSIONS

While the PAM-13 serves as a valuable instrument for comprehending and promoting health-related skills in cancer patients, the identification of ceiling effects, disordered item-difficulty rankings, and inconclusive findings regarding unidimensionality contribute to the expanding body of evidence, emphasizing the dependency of PAM-13's validity and reliability on distinctive characteristics within the population under investigation. Future research should prioritize refining or adding PAM-13 items to better capture the specific health-related challenges within diverse populations, paving the way for more effective patient engagement strategies in oncology.

TRIAL REGISTRATION NUMBER

DRKS00021779.

A new scale assessing the stressors and rewards of children's hospice work

BACKGROUND

There is a workforce shortage in the children's hospice sector, but there has been little research on the specific challenges of working in this setting and on how these challenges might be alleviated. To identify appropriate interventions to improve staff wellbeing, the drivers of wellbeing in children's hospices need to be known and measured. This paper reports on the development of two measures, one for work-related rewards and one for work-related stressors, for use in children's hospice care teams.

METHODS

A mixed-methods, four-stage study; the first three phases focused on the development of the scales, and the last stage focused on the validation of the scales. Participants of all stages were children's hospice care team staff members in the UK. Stage 1: survey assessing the relevance and comprehensiveness of the original scale items (N = 60); Stages 2 (focus groups; N = 16) and 3 (cognitive interviews; N = 14) to assess content validity; Stage 4: UK-wide survey (N = 414) to validate the final version of the new, children's hospice-specific scales using Rasch Analysis (RA) and Confirmatory Factor Analysis (CFA).

RESULTS

Due to poor fitting indices shown in the results from the RA, five items (out of 36) were removed from the new rewards scale used in the UK-wide survey and 20 (out of 62) were removed from the new stressors scale. CFA also supported the removal of the items and showed a one-factor structure for the rewards scale and a three-factor structure for the stressors scale were adequate-the sub-scales for the stressors scale related to caring for an ill or dying child ("Child" sub-scale), working with parents and families ("Parent" sub-scale), and stressors related to organisational factors, such as team conflict and workload ("Organisation" sub-scale).

CONCLUSIONS

Both of the new scales showed good psychometric properties and can be useful in clinical settings and research to assess the perceived intensity of the work-related rewards and stressors for children's hospice staff.

The Functional Rating Index: Twenty Years of Invalid Measurement

STUDY DESIGN

The 2001 Functional Rating Index (FRI) was not developed under today's standard psychometric analysis. The original data of 108 cases were re-analyzed using Rasch item response theory. In 2015, 2 alternative forms were administered to an additional 140 patients for establishing and perhaps improving its psychometric characteristics.

OBJECTIVE

To evaluate the FRI with item response theory.

SUMMARY OF BACKGROUND DATA

The 2001 FRI data showed internal agreement among items and weak item-total correlation items. The FRI's true reliability and validity were never established.

METHODS

The original 2001 FRI 108 and two new versions with 140 respondents with back pain were compared by Rasch analysis for unidimensionality, local independence, monotonicity, and differential item functioning.

RESULTS

All three versions exhibited more than the requisite single latent construct. The original Form 2001 had two items that were non-monotonic, four with differential item functioning (DIF), five with poor infit, and four with poor outfit. Form B had five nonmonotonic items, five had DIF, three had poor infit, and three had poor outfit. Form C had only monotonic items, one item with DIF, three items with poor infit, and two with poor outfit.

CONCLUSION

The original FRI and alternative forms all fail failed crucial psychometric tests and fail to accurately measure more than one latent construct. It is thus unfit as a pain, function, and disability assessment. Only reducing the number of Likert choices improved the test. Other back pain assessments should be used instead, and all surveys would benefit from periodic item responses to adjust to shifts in grammar and meaning.Level of Evidence: 3.

Are we prepared for clinical trials in Charcot-Marie-Tooth disease?

There has been considerable progress in developing treatments for Charcot-Marie-Tooth disease with a number of therapies either completing or nearing clinical trials. In the case of CMT1A, the commonest subtype of CMT, there have been more than five randomised, double blind placebo-controlled trials. Although these trials were negative for the primary outcome measure, considerable lessons have been learnt leading to the collection of large prospective natural history data sets with which to inform future trial design as well as the development of new and sensitive outcome measures. In this review we summarise the difficulties of conducting clinical trials in a slowly progressive disease such as CMT1A and the requirement for sensitive, reproducible and clinically relevant outcome measures. We summarise the current array of CMT specific outcome measures subdivided into clinical outcome measures, functional outcome measures, patient reported outcome measures, biomarkers of disease burden and treatment specific biomarkers of target engagement. Although there is now an array of CMT specific outcome measures, which collectively incorporate clinically relevant, sensitive and reproducible outputs, a single outcome measure incorporating all three qualities remains elusive.

Intraepidermal nerve fibre density as biomarker in Charcot-Marie-Tooth disease type 1A

Charcot-Marie-Tooth disease type 1A, caused by a duplication of the gene peripheral myelin protein 22 kDa, is the most frequent subtype of hereditary peripheral neuropathy with an estimated prevalence of 1:5000. Patients suffer from sensory deficits, muscle weakness and foot deformities. There is no treatment approved for this disease. Outcome measures in clinical trials were based mainly on clinical features but did not evaluate the actual nerve damage. In our case-control study, we aimed to provide objective and reproducible outcome measures for future clinical trials. We collected skin samples from 48 patients with Charcot-Marie-Tooth type 1A, 7 patients with chronic inflammatory demyelinating polyneuropathy, 16 patients with small fibre neuropathy and 45 healthy controls. To analyse skin innervation, 40-µm cryosections of glabrous skin taken from the lateral index finger were double-labelled by immunofluorescence. The disease severity of patients with Charcot-Marie-Tooth type 1A was assessed by the Charcot-Marie-Tooth neuropathy version 2 score, which ranged from 3 (mild) to 27 (severe) and correlated with age (P < 0.01, R = 0.4). Intraepidermal nerve fibre density was reduced in patients with Charcot-Marie-Tooth type 1A compared with the healthy control group (P < 0.01) and negatively correlated with disease severity (P < 0.05, R = -0.293). Meissner corpuscle (MC) density correlated negatively with age in patients with Charcot-Marie-Tooth type 1A (P < 0.01, R = -0.45) but not in healthy controls (P = 0.07, R = 0.28). The density of Merkel cells was reduced in patients with Charcot-Marie-Tooth type 1A compared with healthy controls (P < 0.05). Furthermore, in patients with Charcot-Marie-Tooth type 1A, the fraction of denervated Merkel cells was highly increased and correlated with age (P < 0.05, R = 0.37). Analysis of nodes of Ranvier revealed shortened paranodes and a reduced fraction of long nodes in patients compared with healthy controls (both P < 0.001). Langerhans cell density was increased in chronic inflammatory demyelinating polyneuropathy, but not different in Charcot-Marie-Tooth type 1A compared with healthy controls. Our data suggest that intraepidermal nerve fibre density might be used as an outcome measure in Charcot-Marie-Tooth type 1A disease, as it correlates with disease severity. The densities of Meissner corpuscles and Merkel cells might be an additional tool for the evaluation of the disease progression. Analysis of follow-up biopsies will clarify the effects of Charcot-Marie-Tooth type 1A disease progression on cutaneous innervation.

A longitudinal study of CMT1A using Rasch analysis based CMT neuropathy and examination scores

OBJECTIVE

To evaluate the sensitivity of Rasch analysis-based, weighted Charcot-Marie-Tooth Neuropathy and Examination Scores (CMTNS-R and CMTES-R) to clinical progression in patients with Charcot-Marie-Tooth disease type 1A (CMT1A).

METHODS

Patients with CMT1A from 18 sites of the Inherited Neuropathies Consortium were evaluated between 2009 and 2018. Weighted CMTNS and CMTES modified category responses were developed with Rasch analysis of the standard scores. Change from baseline for CMTNS-R and CMTES-R was estimated with longitudinal regression models.

RESULTS

Baseline CMTNS-R and CMTES-R scores were available for 517 and 1,177 participants, respectively. Mean ± SD age of participants with available CMTES-R scores was 41 ± 18 (range 4-87) years, and 56% were female. Follow-up CMTES-R assessments at 1, 2, and 3 years were available for 377, 321, and 244 patients. A mixed regression model showed significant change in CMTES-R score at years 2 through 6 compared to baseline (mean change from baseline 0.59 points at 2 years, p = 0.0004, n = 321). Compared to the original CMTES, the CMTES-R revealed a 55% improvement in the standardized response mean (mean change/SD change) at 2 years (0.17 vs 0.11). Change in CMTES-R at 2 years was greatest in mildly to moderately affected patients (1.48-point mean change, 95% confidence interval 0.99-1.97, p < 0.0001, for baseline CMTES-R score 0-9).

CONCLUSION

The CMTES-R demonstrates change over time in patients with CMT1A and is more sensitive than the original CMTES. The CMTES-R was most sensitive to change in patients with mild to moderate baseline disease severity and failed to capture progression in patients with severe CMT1A.

CLINICALTRIALSGOV IDENTIFIER

NCT01193075.

Clinical and genetic investigation in Chinese patients with demyelinating Charcot-Marie-Tooth disease

Demyelinating Charcot-Marie-Tooth disease (CMT) is the most common subtype of CMT. It is caused mainly by 17p11.2 heterozygous duplication, but also by mutations in more than 20 genes which affect development and function of Schwann cells. To investigate the profile of genes mutated and clinical features in demyelinating CMT of Chinese descent, we collected a cohort of 44 demyelinating CMT patients and screened them using multiplex ligation-dependent probe amplification (MLPA) and targeted next-generation sequencing (NGS) technology. The MLPA technology revealed that 77.3% demyelinating CMT patients harbored 17p11.2 heterozygous duplication and 6.8% patients harbored heterozygous deletion of exon 6 of MPZ gene, that was further confirmed a novel c.674_675insA mutation in MPZ gene. In the patients with 17p12 heterozygous duplication, 3 sets of independent families were discordant for the CMT phenotype within the same family. The targeted NGS technology revealed that 6 candidate mutations including 1 previously reported mutation (GDAP1: c.571C>T) and 5 novel mutations (SBF2: c.415T>C, c.619G>T, c.1258A>G; GDAP1: c.589delC; PMP22: c.318delT) were found. In conclusion, combined MLPA technique with targeted NGS, the demyelinating CMT genetic diagnostic success rate was increased.

Charcot-Marie-Tooth Disease Type 1A: Influence of Body Mass Index on Nerve Conduction Studies and on the Charcot-Marie-Tooth Examination Score

PURPOSE

Charcot-Marie-Tooth Disease type 1A (CMT1A) is caused by a duplication of the peripheral myelin protein gene 22 at chromosome 17p11.2-12. There is limited data regarding whether body mass index (BMI) affects electrophysiological or clinical data in those with CMT1A.

METHODS

Electrophysiological data, the Charcot-Marie-Tooth examination score (CMTES) and BMI from 101 patients with known CMT1A were obtained and analyzed.

RESULTS

When controlling for age, a higher BMI does not affect ulnar motor nerve conduction studies in those with CMT1A, but rather components of the CMTES (loss of pinprick and motor strength in the lower extremities).

CONCLUSIONS

BMI and clinical components of the CMTES are correlated, but it is uncertain which came first-whether the loss of lower extremity pinprick sensation and motor strength results in a higher BMI or if higher BMI results in these signs.

New developments in Charcot-Marie-Tooth neuropathy and related diseases

PURPOSE OF REVIEW

Charcot-Marie-Tooth disease (CMT) and related neuropathies represent a heterogeneous group of hereditary disorders. The present review will discuss the most recent advances in the field.

RECENT FINDINGS

Knowledge of CMT epidemiology and frequency of the main associated genes is increasing, with an overall prevalence estimated at 10-28/100 000. In the last years, the huge number of newly uncovered genes, thanks to next-generation sequencing techniques, is challenging the current classification of CMT. During the last 18 months other genes have been associated with CMT, such as PMP2, MORC2, NEFH, MME, and DGAT2. For the most common forms of CMT, numerous promising compounds are under study in cellular and animal models, mainly targeting either the protein degradation pathway or the protein overexpression. Consequently, efforts are devoted to develop responsive outcome measures and biomarkers for this overall slowly progressive disorder, with quantitative muscle MRI resulting the most sensitive-to-change measure.

SUMMARY

This is a rapidly evolving field where better understanding of pathophysiology is paving the way to develop potentially effective treatments, part of which will soon be tested in patients. Intense research is currently devoted to prepare clinical trials and develop responsive outcome measures.