CONSORT

What it is

The Consolidated Standards of Reporting Trials (CONSORT) Statement is the foundational reporting guideline for randomized controlled trials (RCTs). It is maintained by the CONSORT Group and endorsed by the EQUATOR Network, and it is the single most widely adopted reporting standard in clinical research, required by hundreds of biomedical journals (ICMJE-aligned), regulators, and HTA bodies. The core statement covers parallel-group, two-arm, individually randomized superiority trials through a structured checklist (25 items in CONSORT 2010; an expanded item set in CONSORT 2025) and a participant flow diagram that traces enrollment, allocation, follow-up, and analysis. CONSORT is a reporting standard: it specifies what a finished trial report must contain so that readers can judge validity, applicability, and reproducibility. It sits alongside its protocol-stage sibling SPIRIT (used before the trial) and a family of design- and content-specific extensions (pragmatic, AI, PRO, cluster, non-inferiority, harms).

When to use

Use CONSORT whenever a study actually randomizes an intervention to participants (or clusters) and the output is a trial report for a peer-reviewed journal, a regulatory submission (FDA/EMA), or an HTA/payer dossier. Within the real-world evidence space the relevant cases are narrow but important: pragmatic randomized trials embedded in routine care and registry-based randomized trials (RRCTs) that randomize but draw eligibility, baseline data, and/or endpoints from claims, EHR, or disease registries. Decision rules for which CONSORT artifact applies: - A unit was randomized → CONSORT (this guideline) is in scope. No randomization → use STROBE (general observational) or RECORD / RECORD-PE (routinely-collected health data / pharmacoepidemiology) instead. - Pragmatic trial in real-world settings → CONSORT extension for pragmatic trials (consort-pragmatic), paired with PRECIS-2 to characterize where the trial sits on the explanatory–pragmatic continuum. - PRO endpoint is primary or key-secondary → CONSORT-PRO (consort-pro). - AI/ML-based intervention → CONSORT-AI (consort-ai). - Writing the protocol, not the report → SPIRIT (spirit), not CONSORT.

What it requires

CONSORT enforces transparent reporting across the trial lifecycle, and several items become load-bearing in registry/pragmatic RWE trials where data are routinely collected rather than purpose-measured: - Trial design and eligibility — explicit design (parallel, allocation ratio), pre-specified eligibility, and settings; in pragmatic/registry trials, how routine-care eligibility was operationalized in the data source. - Randomization and allocation concealment — sequence generation, type (block/stratified), and concealment mechanism; these distinguish a true RRCT from an observational comparison and are what license a causal interpretation. - Outcomes and estimands — completely defined pre-specified primary/secondary outcomes and, under CONSORT 2025, the estimand and handling of intercurrent events; in registry trials this requires that the routinely-collected outcome be a validated phenotype, not a raw code. - Participant flow (the CONSORT diagram) — numbers randomized, receiving intervention, lost to follow-up, excluded, and analyzed per arm. In registry/claims-based trials this is where attrition, disenrollment, and informative censoring must be made visible. - Baseline data, numbers analyzed, and the analysis population — ITT vs per-protocol, and denominators per arm. - Results, harms, ancillary analyses, and limitations — effect sizes with precision, pre-specified vs exploratory subgroups, and harms (CONSORT-Harms). - Registration, protocol availability, and funding — trial registration number, access to the full protocol/SAP, and declared funding/role of sponsor.

When NOT to use — limitations and common misapplications

- It is not for observational/non-randomized studies. Applying CONSORT to a claims- or EHR-based cohort, case-control, self-controlled, or target-trial-emulation study is a category error; randomization is the trigger. Use STROBE or RECORD/RECORD-PE for secondary-data observational work. A target-trial emulation uses CONSORT-like discipline conceptually but is reported under STROBE/RECORD, not CONSORT. - It is not a risk-of-bias instrument and not a quality score. Completeness of reporting is not internal validity. Use RoB 2 (for RCTs) or ROBINS-I (for non-randomized studies) to appraise bias; do not sum CONSORT items into a score. - Using the wrong extension. A pragmatic registry trial reported against the base statement without CONSORT-Pragmatic (or PRECIS-2 positioning) misses the items reviewers care about most — generalizability, routine-care delivery, and pragmatic outcome ascertainment. AI interventions need CONSORT-AI; PRO endpoints need CONSORT-PRO; protocols need SPIRIT. - Checklist-as-theater. Page-number ticks against each item without substantive transparency (e.g., "estimand reported" pointing to a vague sentence) satisfies the form and fails the function. The flow diagram is meaningless if attrition is rolled up rather than itemized by reason and arm.

How it maps to this catalog

CONSORT items map onto concrete RWE methods that implement them in pragmatic and registry-based randomized trials: - Participant-flow and attrition reporting → attrition-and-loss-to-follow-up-rwe (and, for the eligibility funnel from a routinely-collected source, database-feasibility-attrition-funnel-rwe). - Estimand and intercurrent-event reporting (CONSORT 2025) → estimands-ate-att-intercurrent-events-rwe. - Follow-up onset and avoidance of immortal time when randomization and index dates diverge in registry data → time-zero-index-date-alignment-rwe. - Validated registry/claims outcome and eligibility phenotypes underpinning "completely defined outcomes" → diagnosis-phenotype-algorithm-1ip-2op-time-window-rwe and claims-analysis. - Whether the chosen registry/claims source can credibly support the trial's measurements → fit-for-purpose-data-assessment-rwe.

Applied note (registry-based randomized trial in claims/EHR)

Consider an RRCT that randomizes treatment but ascertains the primary endpoint from linked claims. CONSORT compliance here is more than a checklist: the flow diagram must separate randomization attrition from data attrition (disenrollment, loss of linkage), the "completely defined outcome" item demands a validated claims phenotype with reported PPV/sensitivity rather than a single ICD code, and the CONSORT 2025 estimand item should state the intercurrent-event strategy (e.g., treatment policy vs while-on-treatment) given switching and discontinuation observed in routine pharmacy data. Pair the report with consort-pragmatic and PRECIS-2 so reviewers can locate the trial on the pragmatic–explanatory spectrum.