Clinical Pathology: General Principles, Lab Management, Clinical Chemistry

• The FDA considers LDTs medical devices and the laboratories producing them as manufacturers of medical devices.

• The definition of an LDT is a test designed in a laboratory for specific use ONLY in that laboratory.

• The FDA exercises enforcement discretion with regard to LDTs to enable implementation of the newest diagnostics in clinical laboratories in a meaningful time period.

• The FDA’s proposed jurisdiction over LDTs is the subject of debate, particularly from the CMS, which considers LDTs a service offered by the laboratory to ordering physicians without any reagents or devices crossing state borders. Therefore, they argue that the FDA has no authority in regulating LDTs.

• Although LDTs are not actively regulated by the FDA, Clinical Laboratory Improvement Amendments has a strict set of performance criteria that must be established in method validation before releasing patient results. These include, but are not limited to, linearity, reproducibility, analytical sensitivity/specificity, reference range, and recovery/accuracy.

• LDT validation studies should be tailored to address issues specific to the technology being used. For example, ionization suppression experiments should always be included in methods using electrospray ionization–mass spectrometry, despite this not being specifically listed by Clinical Laboratory Improvement Amendments regulations.