The purpose of this study is to determine whether the computerized decision support system 'NHGDoc' is effective in improving quality of primary care in terms of processes of care (e.g. prescribing behavior of physicians) as well as outcomes of care (e.g. hospital admissions, mortality).

Computerized decision support systems are regarded as useful tools to improve quality of care, but their effects are still uncertain. In the Netherlands 'NHGDoc' a computerized decision support system supported by the Dutch College of General Practitioners (NHG) is currently being implemented among more than 1.000 general practices in the Netherlands.

The aim of this study is to evaluate the effects of NHGDoc on quality of care. In addition, we want to gain insight into the barriers and facilitators that affect the systems' impact.

A cluster randomized controlled trial will be conducted among 120 general practices in the Netherlands. Eligible practices will be randomized to receive either the regular NHGDoc modules (control arm) or the regular modules and an additional module on heart failure (intervention arm). The effect evaluation will focus on processes of care (e.g. prescription behavior) as well as on patient outcomes (e.g. hospital admissions, mortality). Additionally, a process evaluation will be conducted, which includes a focus group study and a survey among participating healthcare providers to evaluate the perceived barriers and facilitators to using 'NHGDoc'.

Results of this study will provide insight in the ability of computerized decision support systems and in particular 'NHGDoc' to improve quality of primary care. Whereas the trial focuses on a specific NHGDoc domain - heart failure - we believe our conclusions are relevant to other primary care areas as well, particularly as this study also explores the factors that contribute to the systems' effectiveness.

Inclusion Criteria:

• General practices should use the information system MicroHIS X or Promedico ASP
• NHGDoc should be available in the general practices

Exclusion Criteria:

• General practices that do not meet the inclusion criteria