Laboratory Developed Test (LDT)

Laboratory Developed Test (LDT) designates a diagnostic assay designed, manufactured, validated, and used within a single laboratory, often to address specialised clinical questions where commercial diagnostic kits are unavailable or insufficient. LDTs may detect genetic mutations, measure protein biomarkers, assess infectious disease targets, or evaluate complex multi-analyte signatures used in personalised medicine. These tests are typically implemented in high-complexity laboratories with established quality systems.

The pharmaceutical and biopharmaceutical industry engages with LDTs extensively during biomarker discovery, clinical trial enrolment, and translational research programmes. In early development, LDTs may serve as the first practical diagnostic tool to identify responsive patient subgroups, especially when companion diagnostics are not yet commercially available. LDT performance requires strong analytical validation, including accuracy, precision, sensitivity, specificity, and reproducibility across sample types and instruments. Regulatory expectations around LDT oversight continue evolving, making compliance and documentation increasingly critical for clinical trial credibility and downstream regulatory submissions. As targeted therapies expand, LDTs remain essential in bridging scientific discovery with real-world clinical implementation.