# TPMT and NUDT15 are two questions, not two names for one test

Two gene headings on a thiopurine report can look like a duplicated section. TPMT and NUDT15 are distinct. A result for one should not be copied into the blank space for the other, and a measured TPMT enzyme result should not be silently relabelled as a DNA result.

The [updated CPIC thiopurine guideline manuscript](https://pmc.ncbi.nlm.nih.gov/articles/PMC12997511/) addresses both genes. Its title says “2025 Update”, while the publication appeared in 2026. That detail is a useful reminder to keep the exact edition title and publication date, rather than treating a year printed on the cover as the entire version history.

## Look at the method beside the name

A fictional reader, Priya, has one document headed “TPMT activity” and another with separate TPMT and NUDT15 genotype fields. Priya initially files them as duplicates. On closer inspection, the methods differ. One describes an activity measurement; the other reports genetic assignments.

The useful next step is not to decide which document is better. Priya asks the service to explain what each test measured and how the results are used together in her care. In the saved notes, the activity result keeps its original units and wording. The genotype fields keep their complete assignments and any coverage limitations. A missing NUDT15 field stays missing.

The CPIC manuscript focuses on genotype-based guidance and separates that scope from other assessments. It does not authorise a reader to convert an activity measurement into an allele assignment. A result can be relevant without being interchangeable with another test bearing the same gene name.

## A combined panel still needs separate coverage

The NHS Genomics Education Programme’s [thiopurine overview](https://www.genomicseducation.hee.nhs.uk/genotes/knowledge-hub/thiopurines/) explains why the two genes appear in this setting. It also notes limitations of testing that focuses on selected variants. A reassuring summary for one gene does not establish what was examined in the other.

Imagine a fictional panel table with two rows. The TPMT row contains a result and a coverage note. The NUDT15 row says “not tested”. A compact front-page summary says “thiopurine panel completed”. The completion statement describes the ordered work; it does not turn the untested row into a negative finding.

For the reader, the practical skill is row-by-row copying. Preserve “not tested”, “not detected”, “uncertain” and “assigned” as different states. These distinctions help prevent an incomplete record from becoming a more comprehensive-looking one when shared between services.

## The report and the monitoring plan have different jobs

The NHS education service also provides a [clinical explanation of known TPMT and/or NUDT15 results in non-malignant indications](https://www.genomicseducation.hee.nhs.uk/genotes/in-the-clinic/results-patient-with-a-known-tpmt-and-or-nudt15-genotype-requiring-thiopurines-for-non-malignant-indications/). This is professional educational material with a named context, not a universal instruction for every thiopurine use.

Keeping the indication matters because the same medicine class can appear in different services and treatment plans. A reader should not import a recommendation from an example case into their own prescription. This article uses original fictional document examples only; it does not reproduce or personalise that clinical case.

A genetic result also does not replace the care team’s ongoing monitoring instructions. The report describes tested information at a particular level. It cannot confirm the current blood results, symptoms or treatment circumstances. Keep the monitoring plan as a separate document with its own dates and contact arrangements.

## Build a two-row conversation note

For each gene, record the test type, result wording, sample or report date and tested coverage. Then write the indication as the treating team describes it. If a phenotype label is supplied, keep it beside the corresponding gene rather than turning it into a broad label about all medicines. A filename can include the method too, so an activity report stays identifiable before you open it.

The question can be simple: “Do you have both results, and have I kept the activity and genotype tests distinct?” Follow with “Which edition of guidance applies here?” That is enough to expose a missing document or an ambiguous label without suggesting a treatment change.

If a later report looks different, compare methods before comparing the summary words. A new genetic panel, an older activity measurement and a changed interpretation edition can produce different-looking paperwork for different reasons. A chronological folder with clear test types is more useful than a single “normal/abnormal” badge.

## Scope and source access

Research accessed 4 October 2026: accessible sections of the updated CPIC manuscript and official indexed NHS education pages. The manuscript is a 2025-titled update published in 2026; no live supplementary-table audit is claimed. This article explains record distinctions, not treatment, doses or an individual’s suitability for thiopurines.