Reasons for missing interviews in the daily electronic assessment of pain, mood, and stress.

Electronic diary assessment methods offer the potential to accurately characterize pain and other daily experiences. However, the frequent assessment of experiences over time often results in missing data. It is important to identify systematic reasons for missing data because such a pattern may bias study results and interpretations. We examined the reasons for missing electronic interviews, comparing self-report and data derived from electronic diary responses. Sixty-two patients with temporomandibular disorders were asked to rate pain intensity, pain-related activity interference, jaw use limitations, mood, and perceived stress three times a day for 8 weeks on palmtop computers. Participants also were asked the number of and reason(s) for missing electronic interviews. The average electronic diary completion rate was 91%. The correspondence between self-report and electronic data was high for the overall number of missed electronic interviews (Spearman correlation=0.77, P < 0.0001). The most common self-reported reasons for missing interviews were failure to hear the computer alarm (49%) and inconvenient time (21%). Although there was some suggestion that persistent negative mood and stress were associated with missing electronic interviews in a subgroup of patients, on the whole, the patient demographic and clinical characteristics, treatment, and daily fluctuations in pain, activity interference, mood, and stress were not associated significantly with missing daily electronic interviews. The results provide further support for the use of electronic diary methodology in pain research.