Introduction

The aim of the present study was to cross-culturally adapt and validate the German parent and patient version of the Juvenile Arthritis Multidimensional Assessment Report (JAMAR) [1] in patients with juvenile idiopathic arthritis (JIA). The JAMAR assesses the most relevant parent/patient reported outcomes in JIA, including overall well-being, functional status, health-related quality of life (HRQoL), pain, morning stiffness, disease activity/status/course, articular and extra-articular involvement, drug-related side effects/compliance, and satisfaction with illness outcome.

This project was part of a larger multinational study conducted by the Paediatric Rheumatology International Trials Organisation (PRINTO) [2] aimed to evaluate the Epidemiology, Outcome and Treatment of Childhood Arthritis (EPOCA) in different geographic areas [3].

We report herein the results of the cross-cultural adaptation and validation of the parent and patient versions of the JAMAR in the German language.

Materials and methods

The methodology employed has been described in detail in the introductory paper of the supplement [4]. In brief, it was a cross-sectional study of JIA children, classified according to the ILAR criteria [5, 6] and enrolled from August 2011 to August 2013. Children were recruited after Ethics Committee approval and consent from at least one parent.

The JAMAR

The JAMAR [1] includes the following 15 sections:

  1. 1.

    Assessment of physical function (PF) using 15-items in which the ability of the child to perform each task is scored as follows: 0 = without difficulty, 1 = with some difficulty, 2 = with much difficulty, 3 = unable to do and not applicable if it was not possible to answer the question or the patient was unable to perform the task due to their young age or to reasons other than JIA. The total PF score ranges from 0 to 45 and has three components: PF-lower limbs (PF-LL); PF-hand and wrist (PF-HW); and PF-upper segment (PF-US) each scoring from 0 to 15 [7]. Higher scores indicating higher degree of disability [8,9,10].

  2. 2.

    Rating of the intensity of the patient’s pain on a 21-numbered circle visual analogue scale (VAS) [11].

  3. 3.

    Assessment of the presence of joint pain or swelling (present/absent for each joint).

  4. 4.

    Assessment of morning stiffness (present/absent).

  5. 5.

    Assessment of extra-articular symptoms (fever and rash) (present/absent).

  6. 6.

    Rating of the level of disease activity on a 21-circle VAS.

  7. 7.

    Rating of disease status at the time of the visit (categorical scale).

  8. 8.

    Rating of disease course from the previous visit (categorical scale).

  9. 9.

    Checklist of the medications the patient is taking (list of choices).

  10. 10.

    Checklist of side effects of medications.

  11. 11.

    Report of difficulties with medication administration (list of items).

  12. 12.

    Report of school/university/work problems caused by the disease (list of items).

  13. 13.

    Assessment of HRQoL, through the Physical Health (PhH), and Psychosocial Health (PsH) sub-scales (5 items each) and a total score. The four-point Likert response, referring to the prior month, are ‘never’ (score = 0), ‘sometimes’ (score = 1), ‘most of the time’ (score = 2), and ‘all the time’ (score = 3). A ‘not assessable’ column was included in the parent version of the questionnaire to designate questions that cannot be answered because of developmental immaturity. The total HRQoL score ranges from 0 to 30, with higher scores indicating worse HRQoL. A separate score for PhH and PsH (range 0–15) can be calculated [12,13,14].

  14. 14.

    Rating of the patient’s overall well-being on a 21-numbered circle VAS.

  15. 15.

    A question about satisfaction with the outcome of the illness (Yes/No) [15].

The JAMAR is available in three versions, one for parent proxy-report (child’s age 2–18), one for child self-report, with the suggested age range of 7–18 years, and one for adults.

Cross-cultural adaptation and validation

The process of cross-cultural adaptation was conducted according to international guidelines with 2–3 forward and backward translations. In those countries for which the translation of JAMAR had been already cross-cultural adapted in a similar language (i.e., Spanish in South American countries), only the probe technique was performed. Reading comprehension and understanding of the translated questionnaires were tested in a probe sample of ten JIA parents and ten patients.

The participating centres were asked to collect demographic and clinical data along the JAMAR questionnaire in 100 consecutive JIA patients or all consecutive patients seen in a 6-month period and to administer the JAMAR to 100 healthy children and their parents.

The statistical validation phase explored the descriptive statistics and the psychometric issues [16]. In particular, we evaluated the following validity components: the first Likert assumption [mean and standard deviation (SD) equivalence]; the second Likert assumption or equal item-scale correlations (Pearson r: all items within a scale should contribute equally to the total score); third Likert assumption (item internal consistency or linearity for which each item of a scale should be linearly related to the total score that is 90% of the items should have Pearson r ≥ 0.4); floor/ceiling effects (frequency of items at lower and higher extremes of the scales, respectively); internal consistency, measured by the Cronbach’s alpha, interscale correlation (the correlation between two scales should be lower than their reliability coefficients, as measured by Cronbach’s alpha); test–retest reliability or intra-class correlation coefficient (reproducibility of the JAMAR repeated after 1 or 2 weeks); and construct validity in its two components: the convergent or external validity which examines the correlation of the JAMAR sub-scales with the six JIA core-set variables, with the addition of the parent assessment of disease activity and pain by the.

Spearman’s correlation coefficients (r) [17] and the discriminant validity, which assesses whether the JAMAR discriminates between the different JIA categories and healthy children [18].

Quantitative data were reported as medians with the first and third quartiles and categorical data as absolute frequencies and percentages.

The complete German parent and patient versions of the JAMAR are available upon request from PRINTO.

Results

Cross-cultural adaptation

The German JAMAR was fully cross-culturally adapted from the British English version with two forward and two backward translations with a concordance for 111/123 translations lines (90.2%) for the parent version and 111/120 lines (92.5%) for the child version.

In the probe technique analysis, 121/123 (98.4%) lines of the parent version of the JAMAR were understood by at least 80% of the ten parents tested (median = 100%; range 40–100%); 114/120 (95%) lines of the patient version of the JAMAR were understood by at least 80% of the children (median = 100%; range 40–100%). Lines 51 and 52 were modified according to parents’ indications; lines 1, 40, 49, 50, 51, and 116 were modified according to patients’ indications.

Demographic and clinical characteristics of the subjects

A total of 322 JIA patients and 100 healthy children (total of 422 subjects) were enrolled at eight paediatric rheumatology centres. Three patients did not give the consent to use their data.

In the remaining 319/322 (99.1%) JIA subjects, the JIA categories were 2.8% with systemic arthritis, 36.7% with oligoarthritis, 23.5% with RF negative polyarthritis, 3.1% with RF positive polyarthritis, 5.6% with psoriatic arthritis, 20.4% with enthesitis-related arthritis, and 7.8% with undifferentiated arthritis (Table 1). The distribution of JIA categories resembles the distribution of national cohorts [19].

Table 1 Descriptive statistics (medians first–third quartiles or absolute frequencies and %) for the 319 JIA patients
Full size table

A total of 413/422 (97.9%) subjects had the parent version of the JAMAR completed by a parent (314 from parents of JIA patients and 99 from parents of healthy children). The JAMAR was completed by 362/413 (87.7%) mothers and 51/413 (12.3%) fathers. The child version of the JAMAR was completed by 385/422 (84.1%) children age 5.0 or older. In addition, patients younger than 7 years, capable to assess their personal condition and able to read and write, were asked to fill in the patient version of the questionnaire.

Discriminant validity

The JAMAR results are presented in Table 1, including the scores [median (first–third quartiles)] obtained for the PF, the PhH, the PsH sub-scales and total score of the HRQoL scales. The JAMAR components discriminated well between healthy subjects and JIA patients.

In summary, the JAMAR revealed that JIA patients had a greater level of disability and pain, as well as lower HRQoL than their healthy peers.

Psychometric issues

The main psychometric properties of both parent and child versions of the JAMAR are reported in Table 2. The following “Results” section refers mainly to the parent’s version findings, unless otherwise specified.

Table 2 Main psychometric characteristics between the parent and child version of the JAMAR
Full size table

Descriptive statistics (first Likert assumption)

For all JAMAR items, the median number of missing responses was 1.9% (1.1–5.1%).

The response pattern for both PF and HRQoL was positively skewed toward normal functional ability and normal HRQoL. All response choices were used for the different HRQoL items, whereas a reduced number of response choices were used for PF items 6, 9, 13, 14, and 15.

The mean and SD of the items within a scale were roughly equivalent for the PF and for the HRQoL items, except for HRQoL item 5 (data not shown). The median number of items marked as not applicable was 1% (0–1) for the PF and 3.5% (2–5%) for the HRQoL.

Floor and ceiling effect

The median floor effect was 86.9% (81.2–90.4%) for the PF items, 64.0% (53.5–75.2%) for the HRQoL physical health (PhH) items, and 60.2% (57.0–66.2%) for the HRQoL psychosocial health (PsH) items. The median ceiling effect was 0.3% (0–1%) for the PF items, 1.9% (1–3.8%) for the HRQoL-PhH items, and 2.2% (1.3–2.5%) for the HRQoL-PsH items. The median floor effect was 34.7% for the pain VAS, 32.5% for the disease activity VAS and 31.8% for the well-being VAS. The median ceiling effect was 0% for the pain VAS, 1.9% for the disease activity VAS, and 0% for the well-being VAS.

Equal item-scale correlations (second Likert assumption)

Pearson item-scale correlations corrected for overlap were roughly equivalent for items within a scale for 80% of the PF items, with the exception of PF items 9, 11, and 15, and for 80% of the HRQoL items, with the exception of HRQoL items 1 and 8.

Item internal consistency (third Likert assumption)

Pearson item-scale correlations were ≥ 0.4 for 93% of items of the PF (except for PF item 15) and 100% of items of the HRQoL.

Cronbach’s alpha internal consistency

Cronbach’s alpha was 0.90 for PF-LL, 0.86 for PF-HW, and 0.78 for PF-US. Cronbach’s alpha was 0.87 for HRQoL-PhH and 0.84 for HRQoL-PsH.

Interscale correlation

The Pearson correlation of each item of the PF and the HRQoL with all items included in the remaining scales of the questionnaires was lower than the Cronbach’s alpha.

Test–retest reliability

Reliability was assessed in 10 JIA patients, by re-administering both versions (parent and child) of the JAMAR after a median of 6 days (0–8 days). The intra-class correlation coefficients (ICC) for the PF total score showed a substantial reproducibility (ICC = 0.69). The ICC for the HRQoL-PhH and for the HRQoL-PsH scores showed a fair reproducibility (ICC = 0.34 and ICC = 0.28, respectively).

Convergent validity

The Spearman correlation of the PF total score with the JIA core set of outcome variables ranged from 0.4 to 0.6 (median = 0.6). The PF total score best correlation was observed with the parent global assessment of well-being (r = 0.6, p < 0.001). For the HRQoL, the median correlation of the PhH with the JIA core set of outcome variables ranged from 0.3 to 0.7 (median = 0.5), whereas for the PsH ranged from 0.3 to 0.5 (median = 0.4). The PhH showed the best correlation with the parent’s assessment of pain (r = 0.7, p < 0.001) and the PsH with the parent global assessment of well-being (r = 0.6, p < 0.001). The median correlations between the pain VAS, the well-being VAS, and the disease activity VAS and the physician-centered and laboratory measures were 0.4 (0.2–0.5), 0.4 (0.2–0.5), and 0.4 (0.2–0.5), respectively.

Discussion

In this study, the German version of the JAMAR was cross-culturally adapted from the original standard English version with two forward and two backward translations. According to the results of the validation analysis, the German parent and patient versions of the JAMAR possess satisfactory psychometric properties. The disease-specific components of the questionnaire discriminated well between patients with JIA and healthy controls.

Psychometric performances were good for all domains of the JAMAR with few exceptions: PF item 15 (“bite a sandwich or an apple”) showed a lower items internal consistency. However, the overall internal consistency was good for all the domains. Notably, the ICC for the HRQoL-PhH and for the HRQoL-PsH scores showed a fair reproducibility. In the external validity evaluation, the Spearman’s correlations of the PF and HRQoL scores with JIA core-set parameters ranged from moderate to strong.

The results obtained for the parent version of the JAMAR are very similar to those obtained for the child version, which suggests that children are equally reliable proxy reporters of their disease and health status as their parents. The JAMAR is aimed to evaluate the side effects of medications and school attendance, which are other dimensions of daily life that were not previously considered by other HRQoL tools. This may provide useful information for intervention and follow-up in health care.

In conclusion, the German version of the JAMAR was found to have satisfactory psychometric properties and it is thus a reliable and valid tool for the multidimensional assessment of children with JIA.