Reliability of distance estimation by doctors and patients: cross sectional study

Objective: To assess the reliability and accuracy of distance estimated by doctors and patients. Design: Comparison between estimated and measured distances of six familiar sites around Guy's Hospital, London. Subjects: 100 hospital consultants and 100 patients. Main outcome measures: Median (range) of estimated distances, and mean (SD) of the difference between estimated and measured distances. Results: Both doctors and patients gave a wide range of estimates of distance. The estimates differed by up to 14.6-fold from the measured distances, and the difference between minimum and maximum estimates was up to 62.5-fold. Conclusion: Doctors and patients were inaccurate at estimating distances, which implies that estimates of distances walked are not reliable indicators of a person's health.