[Self perceived burden from informal care: construction of the EDIZ-plus].

To measure the experienced burden by informal carers (N = 2.444), a 15-item Mokken scale has been developed. This concerns an extended version of the EDIZ ("Ervaren druk door Informele zorg"); several items refer to the pressure of time brought by the combination of labour and care and the consequences for the health of the informal carers are added to the EDIZ. We call this new scale the EDIZ-plus; it concerns a reliable one-dimensional and hierarchical scale which extends from o (no burden) to maximum 15 (severe burden). First, the burden manifests itself in feelings of responsibility of the carer, followed by having difficulty with combining work and family tasks and ultimately exceeding all limits due to too many obligations. In most cases this last group does not only deal with conflicts at home or at work and a decline in their own health, they also experience all other problems in the scale. The presumed limit for overburdening is enclosed by the proposition 'caring put too much pressure on me'. This is a score on the EDIZ-plus of nine or higher. Furthermore, the scale has proved to be usable for several population groups, such as carers of partners and children, parents/parents-in-law and carers of different patient populations (people with dementia, mental disability or a chronic disease). The EDIZ-plus is not only suitable because of its reasonable psychometric qualities, but also because of the usability in different populations.