Evidence and references

Every source this pillar rests on, what each one supports, and a register recording which pages carry evidence and which carry argument.

What this means

This page is the evidence register for the health pillar: every source the pillar rests on, the pages that rely on it, and the boundary of what each source supports. A health design system acquires the tone of clinical guidance cheaply, because a citation on each page and a study behind each rule read as authority whether or not the references say what the pages claim. An unchecked reference converts an opinion into an apparent finding, and the conversion is invisible to any reader who does not open the source.

The rule this pillar operates turns on a narrow definition of cited. evidence: cited means a source we can hand you, that we have opened, that says what we say it says. A claim that fails any one of those three conditions is opinion, and it is declared as opinion in the page's own frontmatter where a machine can read it.

Applying that rule across the pillar produces a countable result. Of the 24 pages here, 14 declare evidence: opinion, 10 declare mixed, and none declares cited. The opinion is argued and falsifiable, and every page names the observation that would revise it. The tiers are readable straight from frontmatter with grep -h '^evidence:' content/docs/health/*.mdx, which is the check behind those counts and the reason the register below is a candidate for generation rather than hand maintenance.

The rule

Never invent a citation, a statistic, a date or a study. Prefer an honest opinion to a plausible reference. Every cited claim names a source you can open.

Four rules apply to every page in this section.

evidence is declared in frontmatter on every kind: health page. The field is machine-readable and is emitted into the corpus that agents read, so a downstream consumer can filter on the tier without opening the page body.
cited requires an openable source, which means a DOI, a URL, or a named published standard. The constructions it excludes are "research shows", "studies have found", and a reference reconstructed from memory.
mixed covers a page that carries both tiers. Such a page holds one or two grounded claims alongside several judgements, and its body states which sentence belongs to which tier.
Sources are cited and linked rather than pasted. The NHS Digital Service Manual and other NHS content are Crown copyright and are not reusable, so where this documentation covers the same ground it does so in original prose and points you at the original. Where we name a guideline we do not paraphrase its substance either: a paraphrase fixes the wording at the date it was written, the guideline moves on when it is revised, and the team working from the paraphrase ends up treating a superseded sentence as the requirement.

Sources this pillar rests on

The register below lists every source this pillar cites, the pages that rely on each one, and the proposition it is cited for. A source cited beyond the proposition it actually supports is the failure this register exists to prevent, so the boundary is stated in the last column here rather than left to the page doing the citing.

Source	Kind	Used on	Cited for	What it does not support
Systematic review of laboratory-result presentation formats, JMIR, 2024, DOI 10.2196/53993	Peer-reviewed systematic review	Reference ranges, Numbers, units and precision, Clinical interaction guidelines	That presentation format materially changes what a lay reader takes away from a result	No effect size and no specific visual treatment are extracted from it
Presentation of results in patient portals, BMC Medical Informatics and Decision Making, 2018, DOI 10.1186/s12911-018-0589-7	Peer-reviewed study	Reference ranges, Clinical interaction guidelines	The same claim in the patient-portal context specifically	No effect size and no specific visual treatment are extracted from it
WCAG 2.2, in particular SC 1.4.1 Use of Colour, SC 2.2.2 Pause Stop Hide, SC 2.3.1 Three Flashes, SC 2.3.3 Animation from Interactions and SC 2.5.8 Target Size	Normative standard	The two colour axes, Clinical status semantics, Motion in health UI	Requirements that are checkable against a published standard rather than research findings about readers	The criteria set a floor and do not choose between conforming designs. How this system tests against them is Accessibility
APCA and the WCAG 3 draft contrast work	Draft standard	Contrast and APCA	A second contrast measure, published alongside the WCAG 2.2 ratio	Conformance, which remains the WCAG 2.2 ratio
NHS England information standards DCB0129 and DCB0160, on clinical risk management in the manufacture and in the deployment of health IT	Information standard	Regulatory context	That the obligations exist, are published, and are findable by name	Their requirements, which are named here and never paraphrased
Regulation (EU) 2017/745 on medical devices, and the UK medical devices regime	Regulation	Regulatory context	That software can be a medical device in its own right	The classification of any particular product, which opsinjs never assigns
The FDA's clinical decision support guidance, and the software provisions of the 21st Century Cures Act	Regulator guidance and statute	Regulatory context	Where consumer health products in the United States usually sit, or try to sit	Legal, regulatory or clinical advice of any kind
UK GDPR and EU GDPR special-category provisions	Legislation	Consent and disclosure	That health data is a special category with additional conditions on processing, and that consent as a lawful basis carries statutory requirements	A summary of the law, and the choice of lawful basis, which for direct care is frequently not consent
World Health Organization guidance on responsible communication about suicide, and the Samaritans media guidelines	Named guidance	Crisis and self-harm	That a current, freely available body of safe-messaging practice exists and is more authoritative on it than a design system	Their content, which this register cites and never paraphrases. The interface rules on that page are opinion
The Joint Commission's Sentinel Event Alert on medical device alarm safety in hospitals (Issue 50), and ECRI's health technology hazards lists	Safety alert and hazard register	Alarm fatigue	That alarm fatigue in clinical settings is a documented patient-safety problem rather than a designer's intuition	Transfer of those findings to a consumer phone app, which that page marks as opinion
The NHS Digital Service Manual	Comparison point	Named across this documentation, in the patterns section and in this pillar	How another public-service organisation handles the same ground	Any claim in opsinjs. The text is Crown copyright and is never copied
Apple's Human Interface Guidelines	Comparison point	Notifications and off-screen alerts, Target size and motor accessibility	Current platform behaviour, which is checked against the guidelines rather than restated from them	A safety argument, because a platform convention is a convention rather than a finding, and the guidelines are cited rather than copied

Where we know the evidence is thin

Six topics in this pillar rest on argument where a finding would serve better; five carry evidence: opinion today and one has no page at all. Each row names the topic and the specific item that would move it.

Topic	What is missing
Numeracy and health literacy in the general population	A read, dated, citable review; the qualitative claim on Who this is for stands in for it
Natural frequencies over percentages	The primary risk-communication sources named but not yet read and cited on Risk and statistics
Alert frequency and response in consumer apps	Any field data at all; the budgets on Alarm fatigue are chosen, not derived
Receiving results without a clinician present	Patient-preference research, for Delivering difficult results
Screening statistics and predictive value	The page does not exist yet
Device accuracy across skin tones	Named as a real issue, deliberately unquantified, on Data provenance and device accuracy

Not written yet. Generate the evidence register from page frontmatter rather than maintaining the table above by hand, and have check-freshness report any kind: health page whose reviewed date has expired.

Why (evidence)

mixedas at 2026-09-02

The rule itself is our policy, so this page's mixed marking refers to the sources listed above rather than to the discipline.

The discipline is built around a propagation failure. A design system is copied, so a rule stated here appears unattributed in a product's internal guidelines, and from there in a clinical safety case. By the third level the original wording is gone and the claim is carrying weight it was never given. An opinion marked as an opinion can be weighed by a downstream reader at any of those levels, and an opinion presented as a finding cannot.

The discipline costs this pillar some of its persuasive force. A page that says "this is our judgement" is less persuasive than a page that says "research shows", and some readers will discount it on that basis. We accept the discount, because the alternative is to be more persuasive than we are entitled to be, in a domain where the people relying on us cannot check.

What would change our mind: the discipline is a policy rather than an empirical claim, so no observation about readers would revise it. What changes is the register above, as the sources named in the thin-evidence table are read and the pages that depend on them move tier.

Applying it

"This is our design judgement. Here is the reasoning, and here is what would change our mind." The claim states its basis and the condition under which it would be revised.

Don’t

"Research shows that users prefer…" with no reference. The sentence names no study, no population and no measure, so there is nothing a reviewer can open and nothing a reader can check it against.

Cite the standard by name and number and let the reader open the current version: "WCAG 2.2 SC 1.4.1".

Don’t

Paraphrase the standard's requirement into your own sentence and present the sentence as the requirement. The paraphrase stays fixed while the standard is revised, and a team relying on it is then conforming to a version that no longer exists.

Set evidence: opinion and say so in the body when you are stating a design position. The field is machine-readable, so an agent reading this corpus can weigh the claim without parsing the prose around it.

Don’t

Set evidence: cited and link a search results page, a blog summary, or a reference you have not opened. The link resolves, so the citation survives review, and the claim it appears to support is never checked against a source.

Components that implement this

source-citation ships, and it is the component form of this page's rule: an attributed, dated, linkable claim that can appear next to a value or inside an explanation, so that a product inherits the discipline instead of reimplementing it. It has not been reviewed, and on this site itself the discipline is still carried by frontmatter and prose rather than by the component.

What this does not cover

A literature review. This is a register of what this documentation relies on, not a survey of the field.
Clinical evidence for any threshold, range or intervention. None appears anywhere in opsinjs, and this register cites none.
The freshness mechanism. Review cadence, owners and expiry reporting are Docs freshness.
Licensing of the guidance itself, which is Licence and attribution. The prose in this documentation is separately licensed from the code.

Updates to this page

Last read through against the system on 2026-09-02. Due for review every 6 months; expiry is reported by pnpm run check:freshness.

Evidence and references

On this page