Objective: To assess the impact of clinicians' use of an online information retrieval system on their performance in answering clinical questions.

Design: Pre-/post-intervention experimental design.

Measurements: In a computer laboratory, 75 clinicians (26 hospital-based doctors, 18 family practitioners, and 31 clinical nurse consultants) provided 600 answers to eight clinical scenarios before and after the use of an online information retrieval system. We examined the proportion of correct answers pre- and post-intervention, direction of change in answers, and differences between professional groups.

Results: System use resulted in a 21% improvement in clinicians' answers, from 29% (95% confidence interval [CI] 25.4-32.6) correct pre- to 50% (95% CI 46.0-54.0) post-system use. In 33% (95% CI 29.1-36.9) answers were changed from incorrect to correct. In 21% (95% CI 17.1-23.9) correct pre-test answers were supported by evidence found using the system, and in 7% (95% CI 4.9-9.1) correct pre-test answers were changed incorrectly. For 40% (35.4-43.6) of scenarios, incorrect pre-test answers were not rectified following system use. Despite significant differences in professional groups' pre-test scores [family practitioners: 41% (95% CI 33.0-49.0), hospital doctors: 35% (95% CI 28.5-41.2), and clinical nurse consultants: 17% (95% CI 12.3-21.7; chi(2) = 29.0, df = 2, p < 0.01)], there was no difference in post-test scores. (chi(2) = 2.6, df = 2, p = 0.73).

Conclusions: The use of an online information retrieval system was associated with a significant improvement in the quality of answers provided by clinicians to typical clinical problems. In a small proportion of cases, use of the system produced errors. While there was variation in the performance of clinical groups when answering questions unaided, performance did not differ significantly following system use. Online information retrieval systems can be an effective tool in improving the accuracy of clinicians' answers to clinical questions.