GeraClinic / Diagnostic Waiting Times Index / Methodology
How the Gera Diagnostic Waiting Times Index is calculated
The Gera Diagnostic Waiting Times Index is a reproducible 0–100 score derived entirely from the real NHS England DM01 Diagnostic Waiting Times and Activity release. This page sets out the exact formula, the one disclosed reference ceiling, a worked example, the data provenance and the limitations — so anyone can reproduce or challenge the number.
What the index measures
The index answers one question: how long do patients wait for an NHS diagnostic test in England? It is anchored to the single official DM01 accountability standard — the share of the diagnostic waiting list that has been waiting 6 weeks or more — and expresses it as a 0–100 number, where 0 is close to the operational standard and higher means longer waits.
The NHS standard: fewer than 1% of patients should wait 6 weeks or more for one of the 15 key diagnostic tests. That standard has not been met since November 2013.
The formula
6-week share, scored against a disclosed ceiling
Take the published DM01 “% waiting 6+ weeks” and score it against a 40% reference ceiling — the level at which the index reaches 100. 40% (two in five of the waiting list waiting 6+ weeks) is a documented crisis level, well above the 1% operational standard. The ceiling is the only editorial choice in the index, and it is disclosed here.
GDWTI = min(100, sixWeekSharePct / 40 × 100)
(rounded to 1 dp; higher = longer waits)
Worked example — England, January 2026
- Patients waiting 6+ weeks: 447,068 — about 25.0% (one in four) of the roughly 1,788,272 on the diagnostic waiting list.
- GDWTI = min(100, 25 / 40 × 100) = 62.5 / 100
The total-list figure shown is derived (waiting ÷ share) and labelled as such; the hard published DM01 number is the 6+ week count of 447,068.
Data provenance
The national 6+ week figure is taken from the NHS England DM01 Diagnostic Waiting Times and Activity release. National figures use NHS England’s published England total. The index is the only Gera-computed layer, and it is fully specified above.
Contains public sector information published by NHS England and licensed under the Open Government Licence v3.0. Source: NHS England — Monthly Diagnostic Waiting Times and Activity (DM01) (January 2026, published March 2026).
Contains public sector information published by Gera Systems and licensed under the Open Government Licence v3.0 (source data). Source: Gera Diagnostic Waiting Times Index — derived from NHS England DM01 open data (January 2026, published 3 July 2026).
Data-status policy — no fabrication
Where a cut has been extracted from the DM01 file and checked, it is shown as a real figure. Where it has not — the per-test-type breakdowns and the 13-week severity cut — the page shows an explicit “loads from the DM01 file” state rather than a guessed number. Gera does not display a diagnostic figure it has not verified against the source.
Source file to wire: NHS England DM01 "Monthly Diagnostics Web File" (provider-level CSV/Excel), e.g. Monthly-Diagnostics-Web-File-Provider-<MONTH>-<YEAR>.xls, from the Diagnostics Waiting Times and Activity statistical work area.
What the index does NOT show
- It covers England only, and only the 15 DM01 tests — not every investigation the NHS does.
- It measures the wait to be tested, not the wait for treatment once a diagnosis is made.
- The 6-week benchmark is an accountability standard, not a clinical-urgency threshold; an urgent case is prioritised regardless of the average wait.
- It is a monthly summary. For a serious or life-threatening emergency, always go to A&E or call 999.
- This page is information, not medical advice. For any decision about your own care, use NHS 111 or speak to a clinician.
Update cadence
NHS England publishes DM01 diagnostic waiting-time data monthly. Gera recomputes the index on each release. The national figure here is for January 2026 and was last recompiled on 3 July 2026.