The aim of the present study was to cross-culturally adapt and validate the Croatian parent, child/adult 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 Croatian 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 September 2013 to April 2016. Children were recruited after Ethics Committee approval and consent from at least one parent.


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 3 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 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) subscales (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 10 JIA parents and 10 patients.

Each participating centre was asked to collect demographic, clinical data and the JAMAR 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 items-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 6 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 1st and 3rd quartiles and categorical data as absolute frequencies and percentages.

The complete Croatian parent and patient versions of the JAMAR are available upon request to PRINTO.


Cross cultural adaptation

The Croatian JAMAR was fully cross-culturally adapted from the standard English version with 2 forward and 2 backward translations. The concordance rate between the original standard English version of the JAMAR and the 2 back-translations was 91.7% (112/123 lines) for the parent version and 91.1% (110/120 lines) for the child version.

All 123 lines of the parent version of the JAMAR were understood by at least 80% of the 10 parents tested (median = 100%; range 90–100%). All the 120 lines of the patient version of the JAMAR were understood by at least 80% of the children (median = 100%; range 90–100%). The text of the parent and child JAMAR was unmodified after the probe technique.

Demographic and clinical characteristics of the subjects

A total of 100 JIA patients and 100 healthy children (total of 200 subjects), were enrolled at the paediatric rheumatology centres of the Clinical Hospital Center Sestre Milosrdnice and Children’s Hospital Srebrnjak in Zagreb.

In the 100 JIA subjects, the JIA categories were 7% with systemic arthritis, 38% with oligoarthritis, 19% with RF negative polyarthritis, 5% with RF positive polyarthritis, 12% with enthesitis related arthritis and 19% with undifferentiated arthritis (Table 1). Notably, none of the enrolled JIA patients is affected with psoriatic arthritis.

Table 1 Descriptive statistics (medians, 1st 3rd quartiles or absolute frequencies and %) for the 100 JIA patients

A total of 192/200 (96%) subjects had the parent version of the JAMAR completed by a parent (93 from parents of JIA patients and 99 from parents of healthy children). The JAMAR was completed by 151/192 (78.6%) mothers and 41/192 (21.4%) fathers. The child version of the JAMAR was completed by 180/200 (90%) children age 5.5 years or older. Also patients younger than 7 years old, 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 (1st–3rd quartile)] obtained for the PF, the PhH, the PsH subscales 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 a 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

Descriptive statistics (first Likert assumption)

For all JAMAR items, the median number of missing responses were 2.2% (1.1–5.9%).

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 except for items 8 and 9, whereas a reduced number of response choices was used for all the PF items except for items 1, 2, 3, 4 and 5.

The mean and SD of the items within a scale were roughly equivalent for the PF and for the HRQoL items (data not shown). The median number of items marked as not applicable was 1% (0–2%) for the PF and 2% (1–3%) for the HRQoL.

Floor and ceiling effect

The median floor effect was 88.2% (82.8–93.5%) for the PF items, 60.2% (43–64.5%) for the HRQoL PhH items, and 62.4% (48.4–69.9%) for the HRQoL PsH items. The median ceiling effect was 0.0% (0–1.1%) for the PF items, 3.2% (2.2–3.2%) for the HRQoL PhH items, and 1.1% (0–1.1%) for the HRQoL PsH items. The median floor effect was 43% for the pain VAS, 46.2% for the disease activity VAS and 55.9% for the well-being VAS. The median ceiling effect was 0% for the pain VAS, 3.2% for the disease activity VAS and 1.1% for the well-being VAS.

Equal items-scale correlations (second Likert assumption)

Pearson items-scale correlations corrected for overlap were roughly equivalent for items within a scale for 80% of the PF items, with the exception of items 11, 12 and 15 and for 80% of the HRQoL items, with the exception of items 8 and 9.

Items internal consistency (third Likert assumption)

Pearson items-scale correlations were ≥ 0.4 for 87% of items of the PF (except for items 11 and 15) and 80% of items of the HRQoL (except for items 8 and 9).

Cronbach’s alpha internal consistency

Cronbach’s alpha was 0.87 for PF-LL, 0.91 for PF-HW, 0.45 for PF-US. Cronbach’s alpha was 0.88 for HRQoL PhH and 0.74 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, with the exception of PF items 13 and 14.

Test–retest reliability

Reliability was assessed in 9 JIA patients, by re-administering both versions (parent and child) of the JAMAR after a median of 7 days (7–7 days). The intraclass correlation coefficients (ICC) for the PF total score showed an almost perfect reproducibility (ICC = 0.95). The ICC for the HRQoL PhH and for HRQoL PsH scores showed an almost perfect reproducibility (ICC = 0.96 and ICC = 1.0, respectively).

Convergent validity

The Spearman correlation of the PF total score with the JIA core set of outcome variables ranged from 0.2 to 0.6 (median = 0.3). The PF total score best correlation was observed with the global assessment of well-being (r = 0.6, p < 0.001). The correlation of the PF total score with the ESR and with the number of active joints was not significant (p = 0.41 and p = 0.14, respectively). For the HRQoL, the median correlation of the PhH with the JIA core set of outcome variables ranged from 0.1 to 0.6 (median = 0.3), whereas for the PsH ranged from − 0.1 to 0.4 (median = 0.2). The PhH and the PsH showed the best correlation with the parent’s global assessment of well-being (r = 0.6 and r = 0.5, respectively, p < 0.001). The median correlations between the pain VAS, the well-being VAS, and the disease activity VAS and the physician-centred and laboratory measures were 0.3 (0.2–0.4), 0.2 (0.2–0.3), 0.2 (0.1–0.2), respectively.


In this study, the Croatian version of the JAMAR was cross-culturally adapted from the original standard English version with 2 forward and 2 backward translations. According to the results of the validation analysis, the Croatian 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. The PhH, the PsH subscales and total score of the HRQoL scales proved to discriminate between the different JIA subtypes.

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: 2 PF items (“stretch arms” and “bite a sandwich or an apple” and “having trouble getting alone with other children” and “having difficulty concentrating or paying attention”) showed a lower items internal consistency. However, the overall internal consistency was good for all the domains, with the exception of the PF-US Cronbach’s alpha.

In the external validity evaluation, the Spearman’s correlations of the PF and HRQoL scores with JIA core set parameters were weak.

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 Croatian 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.