Apparently a crap load:
Several studies have identified the overuse of daily lab testing and how certain interventions can effectively reduce tests ordered. A study by Miyakis et al. examined the effects of disclosing lab test costs on the frequency at which healthcare providers ordered these tests. 24,482 laboratory tests were ordered before the intervention (mean 2.96 tests/patient/day). Among those, roughly 70% were not considered to have contributed towards management of patients (mean avoidable 2.01 tests/patient/day). After costs of tests were disclosed, the avoidable tests/patient/day were significantly decreased (mean 1.58, p = 0.002), but containment of unnecessary ordering of tests gradually waned during the semester after the intervention. (1) A study by Kumwilaisak et al. examined how the implementation of formal guidelines effected how laboratory tests were ordered. 1,117 patients were enrolled. After the institution of the guidelines, the number of laboratory tests decreased by 37% (from 64,305 to 40,877). Furthermore, this result was still present at 1 year. (3)