γ-Glutamyl Transferase Testing, Change of Its Designation on the Laboratory Request Form, and Resulting Ratio of Inappropriate to Appropriate Use

Objectives: To determine the effect of a modified request form on the total use of γ-glutamyl transferase (GGT) usage and the ratio of inappropriate testing.

Methods: We modified a test request form by moving GGT from the "Liver profile" to the "Other" section. The criteria for appropriate GGT ordering were developed based on literature review and then validated by expert consensus. To determine the appropriateness of GGT requests, we reviewed the medical records of patients for whom GGT testing was requested, before and after the change in the request form.

Results: The total number of GGT tests performed was reduced from 81,020 tests before the change to 35,816 tests after the change (a 44.2% reduction). Of the 349 patients whose records we examined, GGT testing was ordered for 169 patients before the change in the form and for 180 patients after the change. The percentage of inappropriate GGT ordering was nonsignificantly reduced (from 85.8% to 81.7%; P =.30).

Conclusions: The change in the classification of GGT testing on the laboratory request form was associated with a reduction in total test usage and nonsignificantly associated with a reduction in the proportion of inappropriate testing. Hence, we strongly recommend that physicians be given feedback and education concerning clinical indication.