ICH Q2(R2) Analytical Procedure Validation: Which Tests Apply, What Changed from Q2(R1), and How It Pairs with Q14

ICH Q2(R2) Validation of Analytical Procedures and ICH Q14 Analytical Procedure Development were adopted at Step 4 on the same day — 1 November 2023 — and are designed to be read together. Q14 covers how you develop an analytical procedure and manage it across its lifecycle; Q2(R2) covers how you prove the finished procedure is fit for its intended purpose. Most content still online describes Q2(R1) alone, which was the operative text from 2005 and which Q2(R2) restructured rather than lightly edited. This page sets out which validation tests Q2(R2) expects for which kind of measurement, exactly what changed from Q2(R1), and where the Q2/Q14 boundary falls.

It also separates three obligations that get conflated in practice and carry different evidence requirements: validation (ICH Q2, for procedures you are registering), verification (for a compendial procedure you are adopting unchanged), and transfer (for moving a validated procedure to another laboratory).

Q2(R2) at a glance: scope, status and the Q14 pairing

Q2(R2) applies to analytical procedures used for release and stability testing of commercial drug substances and products. Section 1.2 also says it can be applied to other procedures forming part of the control strategy under ICH Q10 on a risk-based basis, and that the scientific principles can be applied in a phase-appropriate manner to procedures used during clinical development. The named uses are assay, potency, purity, impurity (quantitative or limit test), identity, and other quantitative or qualitative measurements.

The division of labour with Q14 is stated in both documents rather than implied:

Two consequences of the pairing are worth stating plainly, because they change what a validation package contains:

• Robustness normally moves out of the validation study. Q2(R2) §2 says robustness is typically evaluated as part of development, prior to executing the validation study, and §3.4 points the reader to Q14 for detail. Q2(R2) keeps a robustness section but does not put robustness in the validation-test table — and neither did Q2(R1), which said explicitly that robustness “is not listed in the table but should be considered at an appropriate stage in the development of the analytical procedure.”
• Development data can be used as validation data. Q2(R2) §2 states that suitable data derived from development studies under Q14 can be used as part of validation data. Q14 §2 says the same from the other side, giving robustness data from a design-of-experiments study as its example, and adds that such studies do not necessarily need to be repeated.
• Platform procedures get abbreviated validation. Q2(R2) §2: when an established platform analytical procedure is used for a new purpose, validation testing can be abbreviated if scientifically justified. Q14 §2 adds that certain validation tests can be omitted on a science- and risk-based justification.

Regional status — verify per region, do not assume Step 4 means in force

Step 4 adoption by the ICH Assembly is not the same thing as regional implementation, and the dates genuinely differ:

The error correction is a practical trap. Q2(R2)’s own document history records a 30 November 2023 correction to the reportable-range linearity formulae in Table 5 (dissolution with HPLC as a product performance test for an immediate-release dosage form) on page 25, plus corrections to Tables 6–11 on pages 26–32. If a copy of the guideline circulating in your document management system is the 1 November 2023 file, its Annex 2 example tables are the uncorrected ones. Check the file date before a validation protocol cites an Annex 2 table.

Regional status for other ICH regions (Japan, Health Canada, Swissmedic, and the ICH observers and standing regulatory members) should be checked against that authority’s own implementation page rather than inferred from the EU or US dates above — implementation timing is a regional decision, and this page does not assert dates it has not verified.

Which validation tests apply to which procedure: Q2(R2) Table 1

This is the table most people actually open the guideline for. Q2(R2) organises it by measured quality attribute — identity, impurity (purity), assay — rather than by “type of analytical procedure”, which is how Q2(R1) framed the same decision.

Restated from ICH Q2(R2) Table 1. “Yes” = the test is normally conducted; “No” = the test is not normally conducted. QL = quantitation limit, DL = detection limit. * In some complex cases the DL may also be evaluated for a quantitative impurity test. † Where reproducibility has been performed and intermediate precision can be derived from the reproducibility data set, an independent intermediate-precision study is not required. © International Council for Harmonisation; reproduced under ICH’s public licence with copyright acknowledged.

The four footnotes that carry the actual decisions

The marks in the table are less useful than the notes beneath it, which are where Q2(R2) puts the judgment calls:

1. Routing rule for “other quantitative measurements”. Q2(R2) puts “other quantitative measurements” under both the impurity and the assay column, and resolves the ambiguity by proximity to the limits: a measurement follows the impurity scheme if its range limit is close to the DL/QL, and the assay scheme if the range limit is not close to the DL/QL. That is the deciding question for anything that is neither a classic identity test nor a classic content assay — particle size, water content, a physicochemical property.
2. Technology-inherent justification. Some performance characteristics can be substituted with technology-inherent justification for certain procedures measuring physicochemical properties. Q2(R2) §3.1.1.3 develops this as one of three routes to demonstrating specificity, alongside absence of interference (§3.1.1.1) and orthogonal procedure comparison (§3.1.1.2).
3. Specificity can be compensated, but the wording tightened. Q2(R1) said lack of specificity “could be compensated by other supporting analytical procedure(s)”. Q2(R2) says it should be compensated by one or more other supporting analytical procedures, unless appropriately justified.
4. Accuracy and precision may be combined. New in Q2(R2): §3.3.3 allows assessment against a single combined performance criterion instead of separate accuracy and precision evaluations, using a prediction interval, tolerance interval or confidence interval (other approaches acceptable if justified). If a combined criterion is chosen, §3.3.3.1 requires the result to be reported as a combined value, with the individual accuracy and precision results supplied as supplemental information where relevant.

What actually changed from Q2(R1)

“It was updated” is not a useful summary. Here is the Q2(R1) table, which is what most secondary sources are still describing, in the same format:

Restated from ICH Q2(R1) Table. † In cases where reproducibility has been performed, intermediate precision is not needed. ‡ May be needed in some cases. © International Council for Harmonisation; reproduced under ICH’s public licence with copyright acknowledged.

The eight substantive deltas

1. “Validation characteristic” became “performance characteristic”. Q2(R2)’s glossary defines a performance characteristic as a technology-independent description of a characteristic that ensures the quality of the measured result, and states directly that “previous ICH Q2 versions referred to this as VALIDATION CHARACTERISTIC.” The typical set named is accuracy, precision, specificity/selectivity and range. It is not a cosmetic rename: the same term is now the currency in which a Q14 analytical target profile is written, which is what makes the two guidelines interoperate.
2. Linearity is no longer a standalone characteristic. Q2(R1) listed linearity as one of the eight validation characteristics with its own glossary entry. Q2(R2) has no glossary entry for linearity. It is subsumed into Response (calibration model) under Range, with three sub-cases: linear response (§3.2.2.1), non-linear response (§3.2.2.2) and multivariate calibration (§3.2.2.3). The linear case retains the familiar requirements — a plot of signal against concentration, least-squares regression, the correlation or determination coefficient, y-intercept and slope, residuals assessment, and a minimum of five concentrations distributed across the range. The non-linear case is new in substance: Q2(R2) names four- or five-parameter logistic functions for the S-shaped curves typical of immunoassays and cell-based assays, and requires the model’s suitability to be assessed by non-linear regression analysis.
3. Detection limit and quantitation limit collapsed into one row. Q2(R1) had separate DL and QL rows. Q2(R2) has a single lower range limit row whose cell content names which limit applies: QL for a quantitative impurity test, DL for a limit test. See the LOD and LOQ calculation guide for the arithmetic of the regression-based route.
4. A fourth route to the lower range limit was added. Q2(R1) offered visual evaluation, signal-to-noise, and the standard-deviation-of-response-and-slope calculation. Q2(R2) §3.2.3.4 adds direct validation of the QL by accuracy and precision measurements, rather than estimation followed by confirmation. §3.2.3.5 also adds a proportionality rule worth knowing: where the QL is well below the reporting limit — Q2(R2) gives approximately ten times lower as the example — the confirmatory validation of an estimated QL can be omitted with justification. And for impurity tests, the QL should be equal to or below the reporting threshold.
5. “Specificity” became “specificity/selectivity”. Q2(R2)’s glossary treats them as two terms for the same underlying concept — the extent to which other substances interfere — with specificity describing the ultimate state of measuring an analyte unequivocally and selectivity being relative. This is a deliberate bridge to compendial and regional usage, matching the objective in §1.1 of bridging differences between compendia and ICH member authorities’ documents.
6. Reportable range became an explicit, tabulated requirement. Q2(R1) defined range but gave its examples inside the methodology text. Q2(R2) §2.3 gives reportable range its own section, defines reportable range, working range and reportable result separately in the glossary, and tabulates recommended ranges in Table 2 (below).
7. Multivariate analytical procedures are now in scope. §2.5 and §3.2.2.3 address them directly, and the glossary carries a separate multivariate sub-glossary (calibration set, independent sample and related terms). Q2(R1) had nothing on this.
8. Annex 2 is entirely new. Q2(R1) had no technology-specific worked examples. Q2(R2) Annex 2 provides nine illustrative tables — Table 3 quantitative separation techniques (HPLC, GC, CE, and relative-area quantitation such as charge variants); Table 4 elemental impurities by ICP-OES or ICP-MS; Table 5 dissolution with HPLC; Table 6 quantitative 1H-NMR; Table 7 biological assays; Table 8 quantitative PCR; Table 9 particle size; Table 10 NIR; Table 11 quantitative LC/MS. The annex states these are examples, not mandatory, and that alternative approaches fulfilling the intent may be acceptable.

Two further structural changes are worth noting. Q2(R2) §2.4 gives demonstration of stability-indicating properties its own section, requiring samples containing relevant degradation products in the specificity study — spiked samples with target analytes and known interferences, stressed samples, and aged or stress-stored product samples. And Annex 1 of Q2(R2) is a single figure (Figure 2, “Examples of relevant validation tests based on the objective of the analytical procedure”) illustrating the Table 1 selection logic; it is a graphic rather than text, so consult the guideline PDF directly for it — this page does not attempt to transcribe it.

Reportable range: the actual numbers in Table 2

Q2(R2) §2.3 states that the required reportable range is typically derived from the specification and depends on intended use, that it is confirmed by demonstrating acceptable response, accuracy and precision, and that it should be inclusive of the upper and lower specification or reporting limits. Table 2 gives examples; other ranges may be acceptable if justified, and at low amounts wider upper ranges may be more practical.

Restated from ICH Q2(R2) Table 2. * Where assay and impurity are performed as a single test and only one standard is used, linearity should be demonstrated both for the reporting level of the impurities and up to 120% of the specification acceptance criterion for assay. © International Council for Harmonisation; reproduced under ICH’s public licence with copyright acknowledged.

Note the three distinct range concepts Q2(R2) now defines separately, which are routinely used interchangeably and should not be:

• Range — the interval between the lowest and highest results in which the procedure has a suitable level of precision, accuracy and response.
• Reportable range — all values from the lowest to the highest reportable result for which there is a suitable level of precision and accuracy; typically expressed in the same unit as the specification acceptance criterion.
• Working range — the lowest and highest level of the quality attribute as presented to the analytical instrument, for which the procedure gives reliable results.

The distinction matters when your procedure includes a dilution: the working range is at the instrument, the reportable range is at the specification. Building the calibration that connects them is covered in the analytical calibration curve guide.

Multivariate analytical procedures: what Q2(R2) added

Q2(R2) §2.5 defines a multivariate analytical procedure as one where results are determined through a multivariate calibration model using more than one input variable — its example is a spectrum with many wavelength variables — with the model relating input data to a value for the property of interest. Successful validation should consider calibration, internal testing and validation.

Two requirements from §2.5 have direct practical consequences:

• Samples used for validating quantitative or qualitative multivariate procedures require values or categories assigned to each sample, typically obtained by a reference analytical procedure — meaning a validated or pharmacopoeial procedure.
• Where a reference analytical procedure is used, its performance should equal or exceed the expected performance of the multivariate procedure, and analysis by the reference procedure and multivariate data collection should be performed on the same samples. A reference method that is noisier than the model you are validating cannot demonstrate the model is fit for purpose.

The glossary supports this with a dedicated multivariate section defining terms including calibration set (data with matched known characteristics and measured analytical results) and independent sample (a sample not included in the model’s calibration set). Q14 §8 carries the corresponding development-side content, and Q14 §10.3 addresses documentation for multivariate procedures in a submission.

Validation vs verification vs transfer — three different obligations

These three are conflated constantly, and an audit finding usually turns on having done the wrong one. The short version: validation establishes fitness for purpose for a procedure you are registering; verification confirms that a procedure already validated by a pharmacopoeia performs acceptably in your hands with your matrix; transfer establishes that a receiving laboratory can execute an already-validated procedure.

USP’s chapters are cited here by number only; consult USP–NF directly for their text, which is copyrighted. The relevant trio is <1225> Validation of Compendial Procedures, <1226> Verification of Compendial Procedures and <1224> Transfer of Analytical Procedures. USP General Notices 6.30 is the provision that establishes when a compendial procedure is the official one and what an alternative procedure must demonstrate.

What Q2(R2) itself says about transfer, revalidation and co-validation

Section 2.2, Validation During the Lifecycle of an Analytical Procedure, is compact but load-bearing:

• Revalidation. Changes during the lifecycle may require partial or full revalidation. Science- and risk-based principles can be used to justify whether a given performance characteristic needs revalidation, and the extent depends on which characteristics the change impacts. The glossary defines revalidation as demonstration that a procedure is still fit for purpose after a change to the product, process, or the procedure itself.
• Transfer. Transfer of a validated procedure should be considered in the context of analytical lifecycle changes in line with Q14. When transferring to a different laboratory, a partial or full revalidation of the performance characteristics and/or comparative analysis of representative samples should be performed. Q2(R2) permits omitting additional transfer experiments — but requires that justification for not performing them should be provided if appropriate.
• Co-validation. Defined in the glossary as demonstration that the procedure meets its predefined performance criteria when used at different laboratories for the same intended purpose. §2.2 states that co-validation using data generated at multiple sites could also satisfy the requirements of analytical procedure transfer at the participating sites — a single study serving two obligations, which is the efficiency most transfer plans miss.

Note that Q2(R1)’s revalidation triggers were a fixed list of three: changes in the synthesis of the drug substance, changes in the composition of the finished product, and changes in the analytical procedure. Q2(R2) replaces the list with the risk-based test above. That is a shift from enumeration to justification, and it means a revalidation decision now needs a documented rationale rather than a checkbox against three cases.

What the validation protocol and report must contain

Q2(R2) §2.1 is explicit about documentation, and this is the part inspectors read first:

1. A validation protocol generated before the study. It must contain the intended purpose of the analytical procedure, the performance characteristics to be validated, and the associated criteria.
2. Justification wherever prior knowledge is used — for example knowledge from development studies or from previous studies.
3. An experimental design that reflects the number of replicates used in routine analysis to generate a reportable result. If justified, some validation tests may use a different number of replicates, or the number of replicates in the procedure may be adjusted based on data generated during validation.
4. A validation report summarising the results of the study.
5. Reference materials — or other suitably characterised materials — with documented identity, purity or other characteristics as necessary, used in the study.
6. The methodology used for calculating validation results, submitted alongside the data. Q2(R2) §2 asks for relevant data collected during validation and any methodology used to calculate the results.

Q2(R2) §2 also directs that validation data be submitted in the corresponding sections of the application under ICH M4Q (the Common Technical Document), and that approaches other than those in the guideline may be applicable and acceptable with appropriate science-based justification — with the applicant responsible for designing the validation studies and protocol most suitable for their product.

Two practical points that sit outside Q2 but govern whether the package survives an inspection: the protocol, raw data and report are subject to data-integrity expectations covered in good documentation practices, and any chromatography data system or spreadsheet used to calculate validation results is itself a system requiring qualification — see the computer system validation guide and the IQ/OQ/PQ definition. Where a site runs many such studies, the governing document that scopes them and sets their periodic review is the validation master plan.

How Q14 changes what you file — and what you can change later

The reason Q2(R2) alone is an incomplete picture is that Q14 determines how much regulatory flexibility a validated procedure earns.

• Minimal versus enhanced approach. Q14 §2.1 sets a floor for any development: identify the attributes needing testing; select an appropriate technology and instruments; conduct studies evaluating performance characteristics such as specificity, accuracy and precision over the reportable range (including the calibration model and lower and/or higher range limits) and robustness; and document the procedure including its control strategy. The enhanced approach adds systematic knowledge-building, with anticipated performance criteria documented in an analytical target profile. Q14 states repeatedly that the minimal approach remains valid.
• The analytical target profile (ATP). Q14 §3: an ATP describes the intended purpose, the product attributes to be measured, and relevant performance characteristics with associated performance criteria. It drives technology choice, and once technology is selected it serves as the foundation for deriving the procedure attributes and performance criteria used in Q2 validation. Formal documentation and submission of an ATP is optional — Q14 says so directly — but can facilitate regulatory communication irrespective of development approach.
• Established conditions (ECs). Q14 §6.1, building on ICH Q12: with a minimal approach the number of ECs may be extensive, with fixed parameters and set points. With an enhanced approach, ECs can be reduced and focused on performance when justified by procedure understanding and risk management. ECs may consist of performance characteristics and associated criteria, the analytical procedure principle, system suitability and sample suitability criteria, and set points or ranges for parameters. Where performance criteria or the SST demonstrate a parameter is under control, that parameter may not need to be an EC, or may be assigned a lower reporting category.

That last point is where the commercial value sits: fewer and better-targeted established conditions mean fewer post-approval changes requiring prior approval. Q14 §7 covers lifecycle management and post-approval changes; §9 adds considerations for real time release testing; §10 covers submission of analytical procedure information in CTD format.

Frequently asked questions

Is ICH Q2(R2) mandatory?

ICH guidelines are not self-executing law. They become binding through regional implementation: in the EU, Q2(R2) took legal effect on 14 June 2024 under EMA/CHMP/ICH/82072/2006; in the US, FDA announced the final guidance for industry as available on 7 March 2024, and FDA guidances describe the agency’s current thinking rather than establishing legally enforceable responsibilities. Check the status in each region you file in.

Does Q2(R2) replace Q2(R1)?

Yes — Q2(R2) is a complete revision of the guideline, described in its own document history as undertaken to include more recent application of analytical procedures and to align content with Q14. Q2(R1), titled Validation of Analytical Procedures: Text and Methodology, was the incorporation of the 1996 methodology guideline (Q2B) into the 1994 parent (Q2A), consolidated in November 2005.

Do I still validate linearity?

You still evaluate it, but it is no longer a separate listed characteristic. Q2(R2) folds it into Response (calibration model) under Range, and §3.2.2.1 retains the familiar expectations for a linear response, including a minimum of five concentrations distributed across the range. What changed is that a non-linear response is now explicitly accommodated (§3.2.2.2) rather than treated as an exception, and multivariate calibration has its own subsection (§3.2.2.3).

Which validation tests apply to an identity test?

Per Q2(R2) Table 1, specificity only. Response, lower range limit, accuracy, repeatability and intermediate precision are not normally conducted for an identity procedure. Q2(R2) §3.1.2.1 gives the recommended data for identification specifically.

What is the difference between a limit test and a quantitative impurity test in validation terms?

Both require specificity. The quantitative test additionally requires response (calibration model), accuracy, repeatability and intermediate precision, and its lower range limit is the QL. The limit test requires none of those, and its lower range limit is the DL. Q2(R2) notes that in some complex cases the DL may also be evaluated for a quantitative test.

Do I need to revalidate after transferring a method to a contract laboratory?

Q2(R2) §2.2 says a partial or full revalidation of performance characteristics and/or comparative analysis of representative samples should be performed when transferring to a different laboratory, and that justification should be provided for not performing additional transfer experiments if appropriate. A co-validation study spanning both sites can satisfy the transfer requirement at the participating sites. Independent evidence of a receiving laboratory’s ongoing analytical competence — proficiency testing results, an ISO/IEC 17025 scope of accreditation, or calibration certificates for the instruments involved — supports but does not substitute for the transfer exercise.

Does Q2(R2) apply to clinical trial material?

Its stated scope is release and stability testing of commercial drug substances and products. Section 1.2 adds that the scientific principles can be applied in a phase-appropriate manner to analytical procedures used during clinical development — which is guidance on principles, not an extension of scope. For clinical-trial-specific conduct definitions, see ICH E6(R3) on audit, inspection and monitoring, which is a different guideline family (Efficacy, not Quality).

Where do CLIA and ISO 15189 laboratories fit?

They do not use ICH Q2 as their governing standard. Clinical laboratories in the US work to CLIA performance-specification requirements, and medical laboratories internationally to ISO 15189. The performance characteristics overlap in name — accuracy, precision, analytical specificity, reportable range — but the obligations, thresholds and the regulatory body enforcing them differ. Do not cite Q2(R2) into a CLIA validation package as if it were the applicable standard.

Primary sources

• ICH Q2(R2), Validation of Analytical Procedures, adopted 1 November 2023 (error correction 30 November 2023) — database.ich.org
• ICH Q14, Analytical Procedure Development, adopted 1 November 2023 — database.ich.org
• ICH Q2(R1), Validation of Analytical Procedures: Text and Methodology — database.ich.org
• EMA, ICH Q2(R2) scientific guideline, EMA/CHMP/ICH/82072/2006, legal effective date 14 June 2024 — ema.europa.eu
• EMA, ICH Q14 scientific guideline, EMA/CHMP/ICH/195040/2022, legal effective date 14 June 2024 — ema.europa.eu
• Federal Register notice of availability, Q2(R2) Validation of Analytical Procedures and Q14 Analytical Procedure Development; International Council for Harmonisation; Guidances for Industry; Availability, published 7 March 2024 — federalregister.gov
• USP–NF General Chapters <1224>, <1225>, <1226> and General Notices 6.30 — consult USP–NF directly; text not reproduced here.

Extracts from ICH Q2(R1), Q2(R2) and Q14 are restated on this page under ICH’s public licence, with ICH’s copyright acknowledged. Where a table has been restructured for readability, that is an adaptation, not the original layout — the guideline PDFs above are authoritative.

Related CASRAI guides

• Validation Master Plan (VMP) for a regulated laboratory — the governing document that scopes and schedules validation activity, including analytical procedures.
• Limit of detection vs limit of quantitation — how the lower range limit is actually calculated.
• Building an analytical calibration curve — response, linear range and back-calculation in practice.
• Computer system validation, GAMP 5 and IQ/OQ/PQ — qualifying the instrument and data system behind the procedure.
• Good documentation practices — the data-integrity expectations a validation protocol and report must meet.
• ICH E6(R3) definitions: audit, inspection, monitoring and quality assurance — the Efficacy-side ICH guideline and how its terms differ.
• Proficiency testing and external quality assessment — ongoing evidence of laboratory competence, distinct from validation.
• Laboratory compliance — the full cluster hub.