Division of Rheumatology, Department of Internal Medicine, Cerrahpaa Medical Faculty, University of
stanbul,
1 Division of Rheumatology, Department of Internal Medicine, Marmara Medical Faculty,University of Marmara, stanbul, Turkey and
2 University of London, London, UK
Correspondence to:
V. Hamuryudan, Veysipasa sokak 100, Yil Sitesi I Blok D16, 81190 Uskudarstanbul, Turkey.
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Abstract |
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Methods. Fifty Behçet's syndrome (BS) patients were assessed by four rheumatologists in separate morning and afternoon sessions.
Results. The results showed good intra- and interobserver agreement for the oro-genital ulcers and eye involvement of BS, but there was poor agreement between (kappa score=0.14) and within observers (range for kappa scores 0.090.25) for their overall impression of disease activity. Individual low kappa scores were also noted for erythema nodosum, vascular involvement, central nervous system involvement and gastrointestinal involvement.
Conclusion. These results suggest that the Turkish version of BDCAF may be useful for assessing the classic triad of BS (oro-genital ulceration and eye involvement), but more experience is needed for its other parts.
KEY WORDS: Behçet's syndrome, Disease activity, Behçet's Disease Current Activity Form, Turkish translation, Reliability analysis.
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Introduction |
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There have been previous attempts to develop an internationally accepted disease activity measure [35]. Recently, a new instrument, the Behçet's Disease Current Activity Form (BDCAF), has been developed at the University of Leeds, UK [6]. This form showed good interobserver reliability in a formal study [6] and is now routinely used in the clinic where it has been developed. However, the marked geographical differences in disease expression of BS [7, 8], as well as possible ethnic and intercultural differences in disease impact among individuals from different geographical regions, require the evaluation of this form in other countries before recommending its clinical use universally. We therefore translated the activity form into Turkish and tested its usefulness among Turkish patients.
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Methods |
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Instrument
The Behçet's Current Activity Index has been described in detail elsewhere [6]. In brief, this activity form scores (from 0 to 4) the duration of clinical features (oral ulcers, genital ulcers, skin lesions, etc.) which have been present during the 4 weeks prior to the day of assessment. Eye activity is assessed for the presence or absence of blurring of vision or pain or redness in any eye. Additionally, the patients and clinicians were asked to rate their impressions of the overall disease activity within the preceding 4 weeks by indicating on a scale consisting of seven faces with different expressions.
Translation
A physician who was aware of the purpose of the translation initially translated this form into Turkish. Subsequently, a non-medical person translated it again back into English to assess whether substantial differences in meaning were created during the translation. Finally, two rheumatologists discussed the discrepancies in the translations and made their decisions on the final appearance of the form (the English and Turkish versions of the activity form are available on request).
Design of the study
The study was performed on two different days. Every patient was evaluated twice in one day with separate morning and afternoon sessions. Four rheumatologists took part in the evaluation. To overcome a locality bias, two of them came from another institution in Istanbul, which also has a special interest in BS. All four observers had a brief meeting regarding the use of the form before the evaluation began.
Statistical analysis
Intra-observer reliability was assessed from the morning and afternoon observations of the same observer using Cohen's kappa, a measure of agreement between two raters [10]. Cohen's kappa is sensitive only to the presence or absence of agreement between observers and not to the relative strength of disagreement, when present. All kappas have a maximum value of one (complete agreement), with zero meaning no agreement beyond that which can be expected by pure chance alone.
Interobserver reliability was assessed between all four observers, in both the morning and afternoon. A generalized k-rater kappa described by Fleiss [11] was used for this purpose, which is more properly a generalization of a measure known as Scott's pi [12]. The generalized k-rater kappa is based on the pragmatic assumption that the probability that an object (patient) is assigned to a particular category (severity of manifestation) does not vary across raters.
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Results |
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The completion of the form took ~4 min on average for each observer. The results of the analysis of intra-observer agreement are presented in Table 1. The lowest kappa scorings were obtained for the observer's impression of overall disease activity using the seven different faces. Moderately low kappa scorings were also obtained for erythema nodosum (three observers), pustules (one observer), gastrointestinal involvement (one observer), central nervous system (one observer) and vascular involvement (two observers).
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Discussion |
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Our study demonstrated poor agreement between and within observers for their impressions of overall disease activity. However, this result is not surprising [13] and indeed explains the necessity of attempts to develop reliable disease activity measures. This disagreement, we believe, is most probably the consequence of the heterogeneous nature of organ involvement in BS.
Our results are somewhat different from the findings in the English study, which showed a better reliability of the form [6]. The translation process into Turkish differs from the proposed guidelines for cross-cultural adaptation of health-related quality of life measurements only by the absence of a pre-test phase [14], but none of the patients involved in our study volunteered difficulty in understanding the questions. Thus, before considering an essential construction problem for the parts with low agreement, we have to consider the fact that our colleagues from the UK probably had more clinical experience with the use of the activity form, since it was originally developed by them.
This activity form does not have an overall activity score, i.e. a composite index, deduced from the individual scores for different organ systems. The heterogeneous nature of disease expression in BS, both within and between organ systems, makes this difficult to achieve. Furthermore, one can also debate whether such a composite index would jeopardize accuracy in seeking simplicity. On the other hand, this has been achieved in systemic lupus erythematosus, a condition at least as heterogeneous as BS [15].
We conclude that some parts of the BDCAF (oro-genital ulcers and eye involvement) can be reliably translated into Turkish. However, more experience is needed before all parts of it can be used confidently in daily care and clinical trials. Furthermore, the ultimate test of its usefulness will be to observe its sensitivity and specificity to change over time, and this can only be assessed with its more widespread and dedicated use.
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References |
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