A 12-year Follow-up in Sporadic Inclusion Body Myositis

An End Stage With Major Disabilities

Fieke M. Cox; Maarten J. Titulaer; Jacob K. Sont; Axel R. Wintzen; Jan J. G. M. Verschuuren; Umesh A. Badrising

Disclosures

Brain. 2011;134(11):3167-3175. 

In This Article

Patients and Methods

Patients

From 1996 to 2000, 64 patients fulfilling the European Neuromuscular Centre criteria (Verschuuren et al., 1997) for definite (n = 58) or probable (n = 6) sporadic IBM participated in a cross-sectional nation-wide study, which resulted in a description of the clinical characteristics of the disease (Badrising et al., 2005). A subgroup of 44 patients also participated in a clinical trial comparing weakness progression during 48 weeks of treatment with methotrexate or placebo, which showed no statistical difference (Badrising et al., 2002).

All patients were invited to participate in the present study. For those who had died since the initial assessment, the date and cause of death were retrieved from their medical records by contacting their general practitioner or the treating physician in the hospital or nursing home.

Investigations

The surviving patients underwent investigations following the same protocol as the first assessment (Badrising et al., 2005). These included recording case history, manual muscle testing of 32 muscle groups according to the six-point British Medical Research Council scale (Saunders, 2000) and quantitative testing of 14 muscle groups using a hand-held myometer (van der Ploeg et al., 1991), resulting in a sum score. Three functional grading scales were completed. Both the Barthel index (Mahoney and Barthel, 1965), a measure of physical disability ranging from 0 to 20 and the Rivermead mobility index (Collen et al., 1991), a measure of disability related to mobility ranging from 0 to 15, were used—a lower score representing poorer function. The Brooke's functional grading scale (Brooke, 1986), a motor function measure scale ranging from 3 to 23 where 23 is the worst score, was also applied. Furthermore, a standardized questionnaire dealing with dysphagia (Wintzen et al., 1994) was administered. The type of dysphagia was subdivided into symptoms of impaired propulsion or aspiration (Cox et al., 2009).

HLA typing was performed at baseline in 53 of 64 patients by a complement-dependent lymphocytotoxicity technique using locally prepared sets of anti-HLA allosera and monoclonal antibodies. A few patients were also typed using DNA-based methods (Badrising et al., 2004).

The study was approved by the Ethics Committee of the Leiden University Medical Centre and all patients gave informed consent.

Statistics

Descriptive measures were presented as mean ± standard deviation if appropriate, otherwise as median ± interquartile range. The paired-samples t-test was applied as a means of comparing the different time points, given a normal distribution; otherwise the Wilcoxon signed-rank test was used. For comparison between different groups within the cohort, an independent-samples t-test was used, or Mann–Whitney U-test in case of abnormal distribution. For categorical variables, the Fisher's exact test was used. The rates of decline in strength per year and per 10 years were calculated on manual and quantitative muscle tests, assuming the decline was linear. Correlation tests were performed using Pearson product if appropriate or Spearman's Rank correlation. Time to definitive wheelchair dependency and survival, and factors possibly influencing the latter were calculated using a Kaplan–Meier plot and log-rank tests. Information about Dutch life expectancy and causes of death were gathered from Central Statistics Office of the Netherlands (Statistics Netherlands, 2010). The survival curve for the general Dutch population was generated with adjustment for life expectancy, age at onset and gender for each individual patient. To compare the causes of death in our cohort with those in the general Dutch population, chi-squared tests were used with observed and expected values; in addition, a Bonferroni correction of 14 was applied to correct for multiple comparisons, as we had 14 main categories. Statistical analyses were carried out with SPSS for Windows 16 (SPSS Inc.).

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