Comparison between telephone and self-administration of Short Form Health Survey Questionnaire (SF-36)

Abstract

Objective The characteristics of the 36 item Medical Outcome Short Form Health Study Survey (SF-36) questionnaire, designed as a generic indicator of health status for the general population, allow it to be self-administered or used in personal or telephone interviews. The main objective of the study was to compare the telephone and self-administered modes of SF-36 for a population from Girona (Spain). Methods A randomized crossover administration of the questionnaire design was used in a cardiovascular risk factor survey. Of 385 people invited to participate in the survey, 351 agreed to do so and were randomly assigned to two orders of administration (i.e., telephone-self and self-telephone); 261 completed both questionnaires. Scores were compared between administration modes using a paired t test. Internal consistency and agreement between modalities were analyzed by respectively applying Chronbach's alpha and intraclass correlation coefficients. The effect of the order of administration on the test-retest difference was analyzed by one-way ANOVA for repeated measurements. Results Physical function, physical role and social functioning received significantly lower scores when the self-administered questionnaire was used prior to the telephone survey. When the initial survey was conducted by telephone, all Chronbach's alpha coefficients (except social functioning) scored over 0.70 in the self-administered modality. The intraclass correlation coefficient ranged from 0.41 to 0.83 for the telephone-self order and from 0.32 to 0.73 for the self-telephone order. No clinically significant effect was observed for the order of application. Conclusions The results of the present study suggest that the telephone-administration mode of SF-36 is equivalent to and as valid as the self-administered mode.