ABSTRACT
OBJECTIVE: Missing item values (MIV) often occur in quality-of-life (QoL) questionnaires. This study aimed to examine whether the use of introductory exemplary questions reduces the number of MIV and what patient-related factors influence effectiveness of such a QoL form training. METHODS: In a randomized controlled study in ten primary care practice settings, a total of 215 consecutively recruited patients with at least one chronic disease were requested to complete the Medical Outcomes Study 36 Items Short Form (SF-36) questionnaire, German version 1.0. Prior to filling out the QoL form, a sample of randomly selected patients answered three simple written questions similar in wording and appearance to the original SF-36 questionnaire. RESULTS: In total, 126 (58.6%) patients completed the SF-36 questionnaire without MIV. Despite MIV the forms of 46 (21.4%) patients were still computable, i.e., scoring of scales was possible after use of the standardized SF-36 imputation algorithm. After the imputation procedure, MIV significantly hampered generating computable sum scales in 29 (26.6%) of the control group and 14 (13.2%) of the interventional group (P < 0.05). A univariate analysis suggested no evidence that the number of MIV was reduced by the intervention. However, intervention led to a significant decrease of MIV in males but not in females. The education status affected the number of missing data independent of intervention. CONCLUSION: This cross-sectional study showed that the prior use of three self-created questions similar in wording and appearance to the SF-36 questionnaire significantly reduces MIV in male patients. School qualification of QoL respondents inversely correlated with the number of questionnaire MIV, but independent of education status all subjects did benefit from the QoL form training.
