Clinical Value of Add-on Chemistry Testing in a Large Tertiary-Care Teaching Hospital

Abstract

Background: An add-on request is a new laboratory request made for a previously analyzed specimen. Despite the operational challenges it poses, it remains poorly researched. Objective: To determine the frequency and clinical value of add-on chemistry tests or panels requested to be performed on specimens that had been analyzed by routine testing, for inpatients in a 1000-bed tertiarycare teaching hospital. Methods: Using our Laboratory Information System, we retrospectively reviewed all requests for an add-on chemistry test or panel during a 1-week period. We determined the total number of routine chemistry test or panel requests, the number of add-on requests for chemistry tests or panels, and the number of abnormal results obtained for all add-on-requested tests or panels. We interviewed 65 physicians who had ordered add-on chemistry tests or panels to determine the reasons for their requests. Results: There were 323 requests (3.2% of the 10,094 routine requests) for add-on chemistry tests, as an individual chemistry test (n = 228) or a chemistry panel (n = 95) and at least one abnormal result was obtained in 56.9% (n = 184) of these tests. Of the 65 physicians interviewed, 50 (77%) made the add-on request in response to the results of the original tests or the clinical condition of the patients. Conclusion: Add-on tests appear to provide clinically relevant results and optimize the use of the blood already collected. Laboratories should identify and eliminate inefficient steps in the add-on testing process, such as poor archival practices that may hinder and delay specimen retrieval.