Computers are steadily being incorporated in clinical practice. We con
ducted a nonrandomised, controlled, prospective trial of electronic me
ssages designed to enhance adherence to clinical practice guidelines.
We studied 126 physicians and nurse practitioners who used electronic
medical records when caring for 349 patients with HIV infection in a p
rimary care practice. We analysed the response times of clinicians to
the situations that triggered alerts and reminders, the number of ambu
latory visits, and hospitalisation. The median response times to 303 a
lerts in the intervention group and 388 alerts in the control group we
re 11 and 52 days (p<0.0001), respectively. The median response time t
o 432 reminders in the intervention group was 114 days and that for 36
0 reminders in the control group was over 500 days (p<0.0001). There w
as no effect on visits to the primary care practice. There was, howeve
r, a significant increase in the rate of visits outside the primary ca
re practice (p=0.02), which is explained by the increased frequency of
visits to ophthalmologists. There were no differences in admission ra
tes (p=0.47), in admissions for pneumocystosis (p=0.09), in visits to
the emergency ward (p=0.24), or in survival (p=0.19). We conclude that
the electronic medical record was effective in helping clinicians adh
ere to practice guidelines.