Table 4. The pharmacogenomic information pipeline.

Level of establishment	Current number of described loci with variation that have reached that level (order of magnitude)
Level 1: identification of variation – experimental identification and validation of a human gene variant, submission to a gene variant database, annotation, description and uniform identification of the gene variant as a reference sequence or Locus Reference Genomic entry [27]	4 × 107 (number of human RefSNP clusters in dbSNP)
Level 2: clinical genotype–phenotype association – clinical studies of phenotypes associated with genetic variants (e.g., drug response), deposition in genotype-to-phenotype databases	104 (estimate)
Level 3: approval/recognition – recognition of the clinical significance of the genotype–phenotype association by some authority, for example, mention of impact of genetic variants in package inserts, approval of drugs for patients with specific genotype, clinical validation of companion diagnostics and modification of a national clinical guideline to contain genotype-based decision-making	102 (estimate based on number of US FDA product labels containing pharmacogenomic information [139]
Level 4: significant clinical application – application in clinical practice, possibly recognized as relevant by payers (reimbursement of diagnostic tests, requirement of testing for reimbursement of certain treatments). Implementation of pharmacogenomic guidelines in clinical decision support systems	101 (number of widely documented examples such as warfarin or Herceptin®)
Level 5: surveillance – monitoring of benefit, risk and cost associated with the implementation of a specific pharmacogenomic guideline in clinical practice	? (surveillance not yet established)

We can conceptualize the translation of a pharmacogenomic finding from research (raw data) into practice (established clinical rules that can be implemented in decision support systems) as a continuum with several levels.