Source Hierarchy and Trust Policy

Source Hierarchy and Trust Policy

This page explains how PGY Zero decides what to publish, which sources earn which level of authority, how conflicts between sources are resolved, and where the site's scope ends. Read it once. It governs every factual claim on the site.

What Is a Source Hierarchy?

A source hierarchy is an explicit ranking of evidence types by their resistance to bias and their capacity to support generalizable conclusions. It is not a novelty of this site—it underlies clinical guideline development, systematic review methodology, and graduate medical education itself. Making it explicit for readers serves two purposes: it lets you evaluate any claim on PGY Zero the same way you would evaluate a claim on rounds, and it holds the editorial team accountable to a published standard rather than an informal one.

For a site covering the transition into US residency—a domain where program requirements, application rules, and credentialing standards change on cycles that are not always well-publicized—source discipline is not optional. An applicant who acts on a misattributed or outdated claim may miss a deadline, misread their own competitiveness, or make a ranking decision on false premises. The hierarchy below is the structural answer to that risk.

Tier 1: Primary Literature

The highest evidentiary tier is original research published in peer-reviewed journals, with preference ordered as follows: systematic reviews and meta-analyses, then well-powered randomized controlled trials, then large prospective cohort studies. This preference reflects established evidence-grading frameworks—GRADE, Oxford CEBM, and their derivatives—and not an idiosyncratic editorial preference.

In the context of PGY Zero, Tier 1 sources appear most often in content that touches clinical reasoning development, learning science (how to build durable knowledge for shelf exams and boards), and the documented effects of specific training structures on trainee outcomes. Where a Tier 1 source is cited, the citation identifies author, journal, and publication year. Readers are expected to retrieve and evaluate the primary source independently rather than relying on the site's summary alone.

PGY Zero does not conduct original research. When no Tier 1 source exists for a given claim, the site either moves to a lower tier and labels it accordingly, or declines to make the claim.

Tier 2: Clinical Practice Guidelines

Guidelines issued by recognized professional societies—including but not limited to the ACC/AHA, ACOG, IDSA, AAN, and their peer organizations—constitute Tier 2. They are treated as representing the current synthesis of evidence by domain experts, with the understanding that every guideline carries the methodological and conflict-of-interest profile of its authoring panel.

When PGY Zero references a guideline, the citation identifies the issuing society and the guideline's publication or most recent update year. This matters because guidelines age at different rates depending on the pace of evidence accumulation in that specialty. A guideline published several years ago in a domain with active ongoing trials may already be superseded by emerging practice patterns; one in a domain with stable evidence may remain current. The citation year is provided so readers can make that judgment.

When two society guidelines conflict—for example, when two major bodies recommend different first-line approaches for the same condition—PGY Zero discloses the conflict explicitly rather than choosing one silently. See the Handling Source Conflicts section for the full policy.

Tier 3: Authoritative Textbooks and Reference Works

Recognized medical references—textbooks of the Harrison's and Cecil class, continuously updated clinical decision resources of the UpToDate class, and equivalent specialty-specific references—occupy Tier 3. They are used when Tier 1 or Tier 2 sources are absent, ambiguous, or when a foundational concept requires grounding in accepted clinical framework before primary literature can be interpreted.

Tier 3 sources are acknowledged to carry a specific limitation: textbook publication cycles lag primary literature, and continuously updated references reflect editorial judgment that may not be fully transparent. A claim sourced to Tier 3 is marked as such. Readers should treat it as an orientation to consensus rather than as a settled evidentiary conclusion.

Tier 4: Expert Consensus and Practice Patterns

When no higher-tier source addresses a question that is nonetheless real and consequential for applicants—for example, how program directors describe the weight they give to a specific application component, or how interview practices vary across specialties—PGY Zero draws on expert consensus, case series, survey data from credible sources, and documented practice patterns.

This tier has the highest susceptibility to bias, recency error, and selection effects. Every claim sourced at Tier 4 is labeled explicitly with language such as "based on expert consensus," "reflects commonly reported practice," or "drawn from survey data." Tier 4 claims are never presented as if they carry the evidentiary weight of higher tiers. When a Tier 4 claim concerns something that changes frequently—interview formats, program preferences, application norms—the content carries a review date and a prompt to verify against current sources.

AI-Assisted Synthesis: Role and Limits

PGY Zero uses AI-assisted tools to organize source material, identify structural relationships between concepts, and draft initial content frameworks. This use is disclosed because it is material to how you should read the site.

The editorial policy on AI is narrow and firm: AI tools are used to work with sources, not to originate clinical or application facts. A large language model summarizing a guideline is not the same as the guideline. A model generating plausible-sounding clinical context is not a substitute for a sourced claim. The distinction matters because AI systems can produce fluent, internally consistent text that is factually incorrect or that presents outdated information without flagging it as such.

The human-review layer applied before publication works as follows: every factual claim must be traceable to a named source at the appropriate tier; AI-generated text that cannot be so traced is either sourced and verified or removed; claims about application processes, requirements, and institutional policies are verified against the issuing authority's current documentation before publication. Physician editors—US-trained, with direct experience in the application and training systems covered—review content before it goes live. That review is not a formality; it is the gate through which AI-assisted drafts become published content.

No AI-review process is error-free. The reporting pathway described below exists precisely because this layer will sometimes fail.

How Sources Are Cited in Content

Factual claims in PGY Zero content are cited in line, immediately adjacent to the claim they support, rather than aggregated in a bibliography at the end of a section. The citation convention identifies: for primary literature, author(s) or first author et al., journal name, and year; for guidelines, issuing society and year; for textbooks, title and edition year; for Tier 4 sources, the nature of the source (survey, consensus panel, practice survey) and year.

External links from citations go to the primary source, the society's guideline landing page, or the DOI where available. Where access to the full text requires institutional subscription, the citation links to the abstract or the most accessible point of entry rather than paywalling the claim. PGY Zero does not link to secondary summaries of primary sources as though they were the primary source itself—a summary of a study, however accurate, is not the study.

Content pages display a "last reviewed" date in the header. This date reflects the most recent editorial pass against current sources, not merely the original publication date.

Handling Source Conflicts

Source conflicts arise when two credible sources at the same or different tiers support different conclusions about the same factual question. The editorial policy is as follows.

When a conflict exists between a higher-tier and lower-tier source, the higher tier governs the claim and the lower-tier dissent is either omitted or noted as a minority position with its tier identified. When a conflict exists between two sources at the same tier—most commonly between two society guidelines or two systematic reviews—both positions are presented, the nature of the disagreement is described (different populations, different outcome definitions, different time periods), and neither is presented as definitively settled. A clinical note is added when the conflict has practical decision relevance for the reader.

PGY Zero does not resolve genuine guideline-level disagreements by editorial preference. If two major societies disagree, the reader deserves to know that and to factor it into their own reasoning. Flattening that conflict into a single confident claim would be editorially convenient and epistemically dishonest.

Currency and Review Cadence

Content is reviewed on a scheduled cadence aligned with the natural update cycle of its source tier. Content derived primarily from society guidelines is reviewed within a defined window after any guideline update by the relevant issuing body. Content covering application processes and program requirements is reviewed at each application cycle, because these details can change year to year.

Out-of-cycle updates are triggered by: publication of a high-impact primary study or meta-analysis that materially changes the evidence base for a claim; a guideline update from a major society; a confirmed change to ACGME, NRMP, AAMC, or ECFMG policy; or a validated reader report identifying a factual error. The triggering event and the change made are logged in the version history of the affected page.

The "last reviewed" date on each content page reflects the date of the most recent editorial review, not merely the last time a word was changed. A cosmetic edit does not advance the review date; a substantive evidence check does.

Scope Boundaries: What PGY Zero Does Not Cover

PGY Zero covers the process, strategy, and knowledge base of applying to and beginning US residency training. It does not function as a clinical decision support tool for patient care, a substitute for institutional policy guidance, or a source of legal or financial advice.

The following categories fall outside the site's scope regardless of how the question is framed:

When a reader's question touches these areas, PGY Zero will say so and direct toward the appropriate professional or institutional resource. The site will not attempt to answer questions outside its scope in order to appear comprehensive.

Regarding visa content specifically: PGY Zero describes visa pathways and credentialing requirements in general terms for informational orientation. It does not provide instructional visa guidance. Verify current requirements directly with ECFMG/Intealth and official sources for your application year.

How to Report a Source Concern

Clinicians, researchers, applicants, and program administrators who identify a factual error, an outdated source, a missing citation, or a claim that misrepresents its underlying source are encouraged to report it. The editorial team treats these reports as a core quality mechanism, not as complaints.

Reports can be submitted via the contact form linked in the site footer. A useful report identifies: the URL of the page containing the concern, the specific claim or passage, the nature of the concern (outdated, unsourced, misrepresented, contradicted by a named source), and, if available, a citation or link to the source the reporter believes should govern the claim.

Reports are reviewed by a physician editor. The expected response window is defined on the contact page and reflects current editorial capacity. If a report identifies an error that affects clinical or application decision-making, it is treated as a priority update and the page is flagged as under review in the interim. Reporters receive a response confirming receipt and, upon resolution, a note on the outcome—whether the content was updated, why the existing claim was retained, or why the concern fell outside scope.

Anonymous reports are accepted. You do not need to identify yourself to report a concern.

Relationship to the Medical Disclaimer

This source hierarchy policy and the site's medical disclaimer operate as complementary documents. The source hierarchy describes the evidentiary basis for content—how claims are made, sourced, and maintained. The medical disclaimer describes the liability boundary—what this site is not, what it cannot substitute for, and the conditions under which no amount of sourcing makes a website an appropriate substitute for clinical judgment or professional consultation.

Reading one without the other gives an incomplete picture. The hierarchy tells you how carefully the content was constructed; the disclaimer tells you the irreducible limits of what any carefully constructed website can do. Both apply simultaneously to every page on the site. The medical disclaimer is linked in the site footer and in the header of all clinical content.

Version History of This Policy

Changes to this policy that affect editorial standards, citation conventions, tier definitions, or scope boundaries are logged here with the date of change and a brief rationale. Cosmetic edits are not logged.

Subsequent entries will be added here as the policy is revised. The most recent version of this policy is always the one at this URL.