Different Methods of Screening

Hierarchical (Multi-Tiered) Screening Approaches (HMTS) 

Level 1. Most General Screen - Fast and Simple. This type of screen eliminates the majority of negative candidates, and preferentially does not eliminate potential positives. 

Level 2. Intermediate Screen(s). This step generally employs more specific substrates or semi-quantitative approaches. 

Level 3. Specific Screen. Slowest and most accurate. This type of screen generally employs highly quantitative assays including HPLC, GC, or spec-trophotometric or fluorogenic quantitative approaches. 

---