Frequency that Laboratory Tests Influence Medical Decisions

Background Among the variables that influence medical decisions, laboratory tests are considered to be among the most important and frequently used. The influence of laboratory tests on medical decisions has been difficult to estimate. The goal of this study was to estimate the number of patient encounters that included a laboratory test. Methods We extracted information for 72196 patient encounters from 1-week intervals each quarter of a year from our comprehensive academic medical center electronic medical record. The patients examined represent a comprehensive range of clinical conditions and medical services. We determined for which encounters laboratory and other orders existed. Results Overall 35% of encounters had 1 or more laboratory tests ordered. However, the percent varied markedly with patient care areas. For inpatient, emergency department, and outpatient populations, 98%, 56%, and 29%, respectively, had 1 or more laboratory tests ordered. Conclusions Our observations support that it is not possible to use a single number to categorize the frequency with which laboratory tests occur in patient encounters. Utilization of laboratory tests varied with type of medical service with almost all inpatients, approximately half of emergency department patients, and nearly one-third of outpatients having laboratory tests during their healthcare visit.