Are questions on both achieving and maintaining an erection needed to define erectile dysfunction?

Our aim was to ascertain if the assessment of erectile dysfunction (ED) should include questions on difficulty in both achieving and maintaining erection. A population-based study of 3143 men in Tampere region in Finland was conducted by mailed questionnaire. The 1983 men who responded questions on erectile function were included in the analysis. Different levels in the severity of ED were used to examine the agreement between the two questions. Consistency was measured by kappa coefficient. Consistency was fairly high (kappa=0.71) when the severity of ED was examined in four groups. In those cases where alternative responses were categorized into three groups, consistency was best (kappa=0.86) when the alternatives 'never' and 'sometimes' were combined. Consistency was almost perfect (kappa=0.97) when ED dichotomized into two groups and the cutoff was set between the alternatives 'quite often' and 'intercourse does succeed'. The kappa index was 0.86 with the cutoff level between 'sometimes' and 'quite often' and 0.67 with the cutoff between 'never' and 'sometimes'. When ED was examined in different age groups, the consistency was the highest among the oldest respondents. Responses on both symptoms are needed to distinguish between normal erectile function and minimal ED, and also between minimal and moderate ED, especially in young men. When the aim is to distinguish between complete ED and a milder form, the information from one question is the same as that from two questions.