Cross-cultural adaptation of the JPF-Questionnaire for German-speaking patients with functional temporomandibular joint disorders

Abstract

Clinical research related to the management of the syndrome of temporomandibular joint pain and dysfunction would be facilitated enormously between researchers in different locations around the world if a small number of patient-oriented questionnaires were to achieve wide acceptance. It would make comparison of therapeutic results possible. For this reason, a cross-cultural version of the Jaw Pain and Function (JPF)-Questionnaire was developed and validated for use in German-speaking patients with functional temporomandibular disorders. The scale was translated from the English into the German language and translated back into English again, pretested and reviewed by a committee. The German version of the JPF-Questionnaire was tested on 137 patients with temporomandibular disorders. Reliability and concurrent construct validity were assessed using Pearson's correlation coefficients. The concurrent validity was assessed by evaluating the relation of the questionnaire's summary score (the internal criterion) to data on maximum interincisal distance (the external criterion). Spearman's and correlation coefficients were statistically significant for the comparison of the summary score with maximal mouth opening (r=-0.213; p=0.036). Test-retest reliability for the JPF-Questionnaire was also assessed by Spearman's correlation coefficients: at first admission at the clinic (time a, mean=20.23+/-16.42, median=16), then at the time of administration 1 day later at home (time b, mean=17.98+/-16.29, median=13), and 7 days later at home (time c, mean=17.90+/-15.77, median=13). They were r=0.91 (p=0.0001) for the initial administration with the repetition 1 day later, r=0.90 (p=0.0001) for the initial administration with the repetition 1 week later, and r=0.93 (p=0.0001) for the correlation between the two repetitions. Test - retest reliability measured by mean-against-difference graphs was not satisfactory for time (a) versus time (b) and time (a) versus time (c) but there was a good test-retest reliability for time (b) versus time (c). The use of this instrument can be recommended in future clinical trials, as the German version of the JPF-Questionnaire seems to be valid and--under the same test-retest conditions--reliable for the assessment of temporomandibular joint disorders.