Laboratory-Developed Tests Account for a Small Minority of Tests Ordered in an Academic Hospital System

Abstract

Objectives To determine the frequency of use of laboratory-developed tests (LDTs) in an academic medical center system. Methods Retrospective analysis of 2021 test order data from an academic medical center (hospital, outpatient clinics, and cancer center) was done. Measures included assay type, assay methodology, regulatory status, test order volume, inpatient vs outpatient setting, and provider medical specialty. Results Of the 3,016,928 tests ordered in 2021, 2,831,489 (93.9%) were tests cleared, approved, and/or authorized by the US Food and Drug Administration (FDA); 116,583 (3.9%) were LDTs; and 68,856 (2.3%) were standard methods. These test orders were performed using a total of 1,954 distinct assays. Of these, 983 (50.3%) were FDA assays, 880 (45.0%) were LDTs, and 91 (4.7%) were standard methods. Laboratory-developed tests were more commonly ordered in the outpatient vs inpatient setting and represented a higher proportion of the test volume at the cancer center compared with the university hospital (5.6% vs 3.6%, respectively). The top 167 LDT assays accounted for 90% of the LDT volume (104,996 orders). Among the 20 most frequently ordered LDTs were mass spectrometry assays and tests used in the care of immunocompromised patients. Internal/family medicine placed the greatest number of orders (1,044,642) and ordered one of the lowest proportions of LDTs (3.2%). Conclusions Laboratory-developed tests made up a small percentage of the total laboratory tests ordered within the academic health system studied.

The US FDA's proposed rule on laboratory-developed tests: Impacts on clinical laboratory testing

“…The limited public information on the number and extent of LDTs in use within clinical laboratories has been one justification proposed by the FDA and other groups for additional oversight [ 26 , 31 ]. This does not mean that such information does not exist, however, but rather it is not being collected by federal agencies in a manner that would better inform the public [ 32 ]. For example, and as previously discussed [ 32 ], all clinical laboratories accredited by the College of American Pathologists (a CLIA-approved accreditation organization) are required to maintain a list of LDTs currently in use [ 33 ], although the Centers for Medicare and Medicaid Services (CMS) does not collect this information from the CAP.…”

“…This does not mean that such information does not exist, however, but rather it is not being collected by federal agencies in a manner that would better inform the public [ 32 ]. For example, and as previously discussed [ 32 ], all clinical laboratories accredited by the College of American Pathologists (a CLIA-approved accreditation organization) are required to maintain a list of LDTs currently in use [ 33 ], although the Centers for Medicare and Medicaid Services (CMS) does not collect this information from the CAP. Additionally, all laboratories accredited by the New York State Department of Health (NYSDOH) are subject to an LDT review and approval process prior to use [ 34 ].…”

“…The question of ‘how many’ different types of LDTs are available across clinical laboratories is often confused with the concept of ‘how frequently’ they are ordered by clinicians. In a retrospective study of real-world clinician test orders at a large academic health system, we previously demonstrated that LDTs are ordered far less frequently than is typically portrayed in public discussion [ 32 ]. For example, over one year of all test orders in our health system, approximately 94 % of clinician laboratory orders were for FDA-cleared/approved assays, while only 4 % of clinician orders were for LDTs, and 2 % of clinician orders were for standard methods (e.g., differential cell counts, erythrocyte sedimentation rate, urinalysis, Gram stains, etc.)…”

“…For example, over one year of all test orders in our health system, approximately 94 % of clinician laboratory orders were for FDA-cleared/approved assays, while only 4 % of clinician orders were for LDTs, and 2 % of clinician orders were for standard methods (e.g., differential cell counts, erythrocyte sedimentation rate, urinalysis, Gram stains, etc.) [ 32 ]. Many LDTs were associated with test modifications, including alternative specimen types for which the original assay manufacturer did not seek FDA-clearance/approval in its submissions.…”