Pre-emptive versus Reactive Genotyping

Pre-emptive versus reactive genotyping describes two strategies for timing pharmacogenomic testing relative to prescribing. In the pre-emptive model, patients are genotyped in advance and results are stored so that guidance is ready the moment any relevant drug is considered. In the reactive model, a test is ordered only when a specific drug is about to be prescribed and its result is awaited before treatment. The two approaches differ in cost, turnaround, data availability, and clinical yield.

Definition

Pre-emptive genotyping is the strategy of testing pharmacogenes before any specific drug decision so results are available in advance, whereas reactive genotyping is the strategy of testing only at the time a particular drug is being considered, with prescribing awaiting the result.

Scope

This entry contrasts the pre-emptive and reactive testing models, the rationale and trade-offs of each, and the operational requirements that pre-emptive testing places on data storage and decision support. It draws on early prospective implementation programs that piloted pre-emptive panel testing. It is a reference comparison of strategies, not advice on whether or when to test an individual patient.

Core questions

• What distinguishes pre-emptive from reactive testing?
• What are the trade-offs of each strategy in cost, turnaround, and yield?
• What infrastructure does pre-emptive testing require to be useful later?
• Why might a single panel test be more efficient than repeated single-drug tests?

Key concepts

• Pre-emptive (prospective) testing
• Reactive (point-of-care) testing
• Panel-based multi-gene testing
• Result storage and reuse
• Turnaround time and clinical timing
• Cost and clinical yield trade-offs

Mechanisms

In a reactive workflow, a clinician orders a pharmacogenomic test for a specific drug, then waits for the result before prescribing; turnaround time can delay treatment, and each new drug may trigger a separate test. In a pre-emptive workflow, a multi-gene panel is run ahead of need, the results are stored in the electronic health record, and they are surfaced through clinical decision support whenever an affected drug is later considered, so no test delay occurs at the point of care (Pulley et al., 2012; Roden, 2019). Pre-emptive testing assumes durable storage of results and reliable decision support to retrieve them, because a genotype is lifelong and may inform decisions years after the sample was taken. Early programs such as Vanderbilt's PREDICT demonstrated the operational feasibility of pre-emptive panel testing with embedded decision support (Pulley et al., 2012).

Clinical relevance

Understanding the pre-emptive versus reactive distinction clarifies why some health systems invest in upfront panel testing while others test on demand, and what each implies for data infrastructure. This entry compares strategies at a system level; it does not recommend a testing approach for any individual and is not a basis for ordering or withholding a test.

Evidence & guidelines

Operational evidence for pre-emptive testing comes from prospective implementation programs that paired panel genotyping with electronic decision support and reported on feasibility and uptake (Pulley et al., 2012). Reviews and consortium retrospectives describe how the field has weighed the two strategies as implementation has matured (Roden, 2019; Relling et al., 2019). These describe implementation experience rather than constitute individualized clinical guidance.

History

Early pharmacogenomic testing was largely reactive, ordered drug by drug. As multi-gene panels became affordable and electronic health records matured, institutions began piloting pre-emptive testing, generating and storing results before they were needed. The Vanderbilt PREDICT project, launched in the early 2010s, was a prominent demonstration of operationalized pre-emptive genotyping linked to clinical decision support (Pulley et al., 2012), and the model spread as part of the broader implementation movement chronicled a decade later (Relling et al., 2019; Roden, 2019).

Debates

Is pre-emptive testing worth the upfront cost?

Pre-emptive panel testing avoids point-of-care delays and lets one result inform many future decisions, but it tests genes that may never become relevant for a given patient, so the balance of cost against clinical yield remains debated.

Key figures

• Jill M. Pulley
• Dan M. Roden
• Josh F. Peterson
• Joshua C. Denny

Seminal works

• pulley-2012
• roden-2019

Frequently asked questions

Why store a pharmacogenomic result instead of retesting later?

Germline genotype does not change over a person's life, so a result obtained once can inform prescribing decisions indefinitely, which is the core efficiency argument for pre-emptive testing.

What is the main drawback of pre-emptive testing?

It incurs the cost of testing genes that may never become clinically relevant for a particular patient and requires durable data storage and decision support to deliver value later.