Kratom Proficiency Testing and Interlaboratory Comparisons: How Laboratories Check Their Results

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Kiody scope note: Kiody serves adults 21+ and focuses on ordinary botanical kratom leaf products, including powder and pure-leaf capsules. Kiody does not sell concentrated 7-hydroxymitragynine (7-OH). This article is educational, not medical or legal advice. Laboratory testing does not make a product FDA-approved, establish that it is risk-free, or override federal, state or local law.

The short answer

A laboratory can produce a professional-looking certificate of analysis and still have an unnoticed measurement problem. Proficiency testing helps reveal those problems by asking multiple laboratories to analyze comparable material and then evaluating the results against an assigned value, a participant consensus or another predefined criterion.

That external check matters because routine internal controls can miss a systematic bias. A calibration error, extraction loss, unit-conversion mistake or matrix effect may affect every sample in the same direction. When the laboratory compares only its work with its own prior work, the problem can look like consistency. An outside comparison provides a different reference point.

Proficiency testing is not a permanent badge of accuracy. It is also not the same thing as laboratory accreditation, method validation, a duplicate analysis, a customer split-sample test or a broad quality-assurance program. The strongest laboratory review asks how all of those pieces fit together.

For kratom, the details are especially important. Competence for lead in a food powder does not automatically demonstrate competence for mitragynine in kratom leaf. A microbiology exercise does not validate a 7-OH method. A successful result for a high-concentration extract may say little about performance near a much lower reporting or legal threshold. The analyte, matrix, method, concentration range and way the result is reported all matter.

This guide explains how proficiency testing works, how to read the evidence, what to ask a laboratory or seller, and why two competent laboratories may still report different results.

What is proficiency testing?

Proficiency testing, often shortened to PT, is an organized external evaluation of laboratory performance. A provider distributes test material to participating laboratories. Each laboratory analyzes the material, usually through its ordinary workflow, and reports a result. The provider then compares the results using rules established for that exercise.

The test material may have a value assigned through a reference procedure, preparation data, measurements by expert laboratories or a robust consensus of participant results. The provider may evaluate performance with a z-score, an uncertainty-based criterion, a percentage difference or another scheme-specific rule.

The core idea is simple: the laboratory must demonstrate how its measurement compares with an external benchmark.

The current international standard for organizations that operate proficiency-testing schemes is ISO/IEC 17043:2023. It sets general requirements for the competence and impartiality of PT providers and for consistent operation of PT schemes. ISO/IEC 17043 addresses the provider and scheme. It should not be confused with ISO/IEC 17025, the standard commonly used to accredit testing and calibration laboratories.

The International Laboratory Accreditation Cooperation also publishes ILAC P9:01/2024, a policy governing how accreditation bodies use proficiency testing and interlaboratory comparisons in the accreditation process. These documents reinforce an important point: PT participation is one component of a laboratory competence system, not a substitute for the entire system.

What proficiency testing is not

Several activities can look similar to PT while answering different questions. A careful reviewer should not use the terms interchangeably.

PT is not laboratory accreditation

Accreditation evaluates whether a laboratory has a functioning quality system and technical competence for activities listed on its accredited scope. That review can include personnel, equipment, methods, traceability, records, measurement uncertainty, quality controls and proficiency-testing participation.

A laboratory may pass one PT round but lack accreditation for the method or matrix appearing on a customer report. Conversely, an accredited laboratory can receive an unsatisfactory PT result. The meaningful question is how the laboratory investigated the result and whether the accreditation body accepted the response—not whether the laboratory has never encountered a problem.

A certificate alone is not enough. The laboratory’s current scope should identify the testing location and, with sufficient specificity, the relevant field, matrix, analyte or method. Kiody’s separate guide, How to Verify a Kratom Laboratory and Its ISO/IEC 17025 Scope, explains that review in detail.

PT is not method validation

Method validation asks whether an analytical method is fit for its intended purpose. Depending on the method, validation may evaluate selectivity, accuracy or recovery, precision, range, calibration, detection and quantitation limits, robustness and matrix effects.

PT asks how the laboratory performed on an external challenge at a particular time. A successful PT result supports confidence in performance, but it does not supply all missing validation data. A validated method can also perform poorly if the laboratory uses a degraded standard, miscalculates a dilution or mishandles the test material.

The two activities are complementary. Method validation establishes the expected performance of the method. PT helps check whether real-world laboratory operation remains consistent with competent performance.

PT is not an ordinary duplicate or retest

Testing the same laboratory sample twice can assess repeatability, but both results may share the same bias. The same analyst, instrument, calibration standard, extraction procedure and spreadsheet could reproduce the same error twice.

Retesting can be useful when supported by a written investigation. It should not become a search for a preferred number. Repeated testing without a documented scientific reason can conceal, rather than resolve, an out-of-specification or conflicting result.

PT is not automatically a customer split-sample comparison

A seller may divide a homogenized sample and send portions to two laboratories. That interlaboratory comparison can be informative, especially when no suitable formal PT scheme exists. But it is not automatically formal proficiency testing.

A customer-run comparison may lack a competent provider, verified homogeneity and stability studies, an independent assigned value, predefined evaluation criteria or statistical safeguards. It can still identify a disagreement worth investigating, but the conclusion should match the design.

A quality-assurance program is not always pass/fail PT

This distinction matters when reviewing respected programs operated by the National Institute of Standards and Technology. NIST’s Dietary Supplement Laboratory Quality Assurance Program helps laboratories improve measurement comparability and helps NIST identify needs for reference materials, workshops and measurement services.

NIST expressly explains in its program reports that these quality-assurance exercises are not proficiency tests and are not intended as strict pass/fail evaluations, even though exercises may be conducted according to ISO/IEC 17043 principles. A laboratory should therefore describe participation accurately. “Participated in a NIST quality-assurance exercise” is not the same claim as “passed a NIST proficiency test.”

NIST’s Food Nutrition and Safety Measurements Quality Assurance Program likewise supports measurement comparability across food-related laboratories. These programs demonstrate the value of external comparison, but participation must not be stretched into a product-specific claim that NIST has approved a laboratory, method or kratom product.

How a proficiency-testing round works

Although designs differ, a defensible PT round usually follows a recognizable sequence.

1. The provider defines the measurand and exercise

The provider specifies what participants are expected to determine. That description should be precise. “Alkaloids” is too broad if the exercise actually evaluates mitragynine mass fraction. “Heavy metals” does not tell the reader whether lead, arsenic, cadmium and mercury are all included.

The measurand may include the analyte, matrix, basis and unit. For example:

• lead in a dried botanical powder, reported in milligrams per kilogram;
• Salmonella presence or absence in a defined test portion;
• mitragynine in a powdered botanical matrix, reported as percent by mass;
• 7-OH in a finished article, reported in milligrams per article; or
• water activity at a stated temperature.

Those are different measurement challenges. A laboratory’s result is meaningful only in the context of the challenge it actually completed.

2. The provider prepares and checks the material

The material must be sufficiently homogeneous for the exercise. If one bottle contains much more analyte than another, participant differences may reflect the material rather than laboratory performance. Stability also matters: a material that changes during storage or shipping can distort the comparison.

Formal providers evaluate homogeneity and stability using an exercise-specific plan. The evidence does not mean every particle is identical. It means the variation attributable to the distributed items is controlled well enough for the intended evaluation.

This step is particularly relevant for botanical powders. Particle size, blending, moisture and natural constituent distribution can affect subsamples. A sound exercise must distinguish laboratory performance from the heterogeneity of the material.

3. Laboratories use their routine process

Participants commonly receive instructions, a deadline and reporting format. They may be directed to handle the item like a routine sample. That design can test the complete workflow: receipt, storage, preparation, extraction or digestion, analysis, calculation, review and reporting.

The laboratory should not give the PT item extraordinary treatment merely to earn a favorable score. Special handling can hide weaknesses in the ordinary process. Many laboratory quality systems also restrict collusion or discussion of results before the reporting deadline.

4. The provider establishes an assigned value

The assigned value may come from a reference measurement procedure, formulation or preparation data, certified reference values, expert laboratories or robust participant consensus. Each approach has strengths and limitations.

A metrologically traceable reference value can provide independence from the participant community. A consensus value can be practical when no higher-order reference exists, but a shared method bias among many participants can influence that consensus. The provider should state how the value was assigned and what uncertainty applies.

5. Results are evaluated using stated criteria

One common tool is a z-score, which expresses how far a reported value is from the assigned value relative to a standard deviation selected for the exercise. The sign indicates whether the result is above or below the assigned value; the magnitude indicates distance under that scheme.

In NIST Internal Report 8559, NIST used the following interpretive bands for the exercises in that report: an absolute z-score below 2 was within the consensus or target range; a value between 2 and 3 was marginally different; and a value above 3 was significantly different. Those cutoffs are useful examples, not universal grading rules for every proficiency scheme. The provider’s protocol governs the interpretation.

Some schemes use an En number that incorporates reported uncertainties. Others compare the difference to a fixed regulatory, fitness-for-purpose or percentage criterion. Qualitative microbiology challenges may be evaluated as correct or incorrect detection, sometimes with additional controls or organism-identification expectations.

6. The provider reports performance

The report may show the laboratory’s confidential identifier, submitted value, assigned value, evaluation statistic, participant distribution and method-group information. A summary can help the laboratory see whether a problem is unique to its operation or common to a technique.

A participation certificate may merely prove that a laboratory submitted a result. It may not show whether the result was satisfactory. Buyers should not treat participation and successful performance as synonyms.

7. The laboratory investigates exceptions

An unsatisfactory result should trigger a documented investigation. The laboratory should determine whether the cause affected only the PT item or could affect customer results. Corrective action should address the root cause and include an effectiveness check.

The U.S. Food and Drug Administration’s laboratory quality manual explains that proficiency testing and interlaboratory comparisons can identify problems that internal quality controls may not reveal. FDA’s ORA-LAB.5.9 policy also makes clear that these programs generally evaluate laboratory operation, not an individual employee, unless a one-person operation is the laboratory’s normal process.

Why internal quality control can miss a problem

Internal controls are essential, but they are not infallible. Consider a laboratory that prepares every calibration standard from a reference material whose stated concentration has been entered incorrectly. The calibration curve can look linear. Replicates can agree. Control samples prepared from the same source can fall within internal limits. The entire system may be precise but biased.

External material prepared independently can reveal the bias.

Other problems PT may expose include:

• incomplete extraction of mitragynine or 7-OH from a botanical or finished-product matrix;
• loss of an analyte during sample preparation;
• contamination introduced during digestion or dilution;
• an incorrect moisture or dry-weight correction;
• a milligram-to-microgram or percent-to-ppm conversion error;
• calibration drift not caught by the laboratory’s chosen checks;
• interference mistakenly identified as the target analyte;
• a reporting template that transposes results or units;
• inadequate recovery from a complex extract or capsule matrix;
• a microbiology method that fails to detect an organism in the presence of matrix inhibition; or
• a false-positive result caused by cross-contamination.

PT does not guarantee that every such problem will be caught. It increases the chance of detecting weaknesses through a genuinely independent challenge.

What kratom buyers should match before relying on a PT result

The question is not simply, “Does the laboratory do proficiency testing?” The better question is, “Does the external performance evidence match the test Kiody is relying on?”

Match the analyte

A satisfactory arsenic result does not demonstrate proficiency for lead, even when both appear on the same metals panel. A mitragynine result does not automatically demonstrate 7-OH performance. Chemically related compounds can have different recoveries, stability, interferences and calibration requirements.

For legal-threshold or product-screening work, exact analyte identity matters. “Kratom alkaloids” is not an adequate substitute for identifying each compound evaluated.

Match the matrix

Matrix describes the material surrounding the analyte. Ordinary leaf powder, a pure-leaf capsule, a concentrated extract, a sweetened liquid shot and an isolated compound are not interchangeable matrices.

A method can perform well in a simple solution and poorly in a botanical powder. It can perform well in leaf powder and encounter suppression, interference or recovery problems in a concentrated finished product. A PT result from a reasonably comparable botanical or food powder can provide useful supporting evidence when no kratom-specific scheme is available, but the limitation should be documented.

Match the concentration range

Performance near a method’s quantitation limit can differ from performance at a high concentration. A laboratory that measures a fortified material at 10 milligrams per gram may not have demonstrated reliable quantitation near 0.5 milligrams per gram.

This point is critical when a result is compared with a legal, contractual or internal specification. Evidence should cover, or reasonably bracket, the decision range. If it does not, the laboratory should have other validation, reference-material or interlaboratory data supporting performance there.

Match the measurement basis and unit

Percent, parts per million and milligrams per gram can describe the same mass fraction in different units. Dry-weight and as-received results can differ because moisture is treated differently. A per-serving result depends on the declared serving mass, while a per-container or per-article result answers another question.

Before comparing a PT result with a customer COA, confirm:

• the exact unit;
• whether the value is dry weight or as received;
• whether it describes total product, total alkaloids, a serving, an article or a container;
• any dilution, moisture or sample-mass correction; and
• the number of significant digits the method supports.

Match the measurement type

Quantitative and qualitative tests answer different questions. A laboratory may competently report Salmonella as detected or not detected in a defined test portion without providing a count. An aerobic plate count produces a numerical result. Botanical identity may rely on microscopy, DNA or a chemical fingerprint rather than a single concentration.

PT evidence should be appropriate to the type of conclusion on the COA.

Match the testing location

Large laboratory organizations may operate multiple sites. Instruments, staff, local procedures and scopes can differ. Confirm that the proficiency result applies to the location that performed the Kiody sample—not merely another facility under the same brand.

Proficiency evidence for common kratom test categories

Mitragynine and 7-OH

An alkaloid comparison should identify each analyte, matrix, method or technique, concentration range, reporting basis and evaluation result. Where a formal kratom PT scheme is unavailable, a laboratory may use fortified materials, suitable reference materials or a planned split-sample interlaboratory comparison as additional evidence. Those activities should be described accurately and should not be mislabeled as formal PT.

For 7-OH, performance near the relevant reporting or decision level deserves specific attention. A method intended only for high-concentration products may not be suitable for distinguishing trace-level or low-level results in ordinary botanical leaf.

Heavy metals

External comparisons for lead, arsenic, cadmium and mercury may be available in food, botanical or dietary-supplement matrices. Review every metal separately. Also check whether “arsenic” and “mercury” mean total element measurements or species-specific measurements; those are different analytical tasks.

NIST quality-assurance programs have long supported comparability for nutritional and toxic elements in food and supplement matrices. Participation can be valuable evidence when the matrix and analytes are relevant, but NIST program participation is not a statement that a specific kratom lot passed or that NIST approved the laboratory.

Microbiology

Microbiology PT may challenge a laboratory to detect or enumerate organisms in a food-like matrix. Relevant evidence can include Salmonella, generic E. coli, coliforms, aerobic counts, yeast and mold, depending on the laboratory’s scope and customer specifications.

The test portion, enrichment scheme, matrix inhibition and qualitative versus quantitative design matter. A correct Salmonella result in one PT round is useful, but it does not erase the need for routine positive and negative controls, media checks, environmental controls and method verification.

Pesticides and mycotoxins

Broad panels create a special documentation challenge. A PT item may contain only a small subset of the compounds listed on a commercial COA. A general certificate saying “pesticide proficiency testing” does not prove performance for every pesticide in a 200-compound panel.

Ask which compounds were actually present and evaluated, at what concentrations, in what matrix, and using which technique. The same logic applies to aflatoxins, ochratoxin A and other mycotoxins.

Water activity and moisture

Water-activity comparisons can test instrument calibration, temperature control, sample equilibration and handling. Moisture-content or loss-on-drying comparisons address a related but different measurement. Passing one should not be used as proof of proficiency in the other.

Botanical identity

Identity testing may not fit a conventional numeric PT model. Interlaboratory challenges can still be designed using authenticated materials, unknown samples, microscopic features, DNA sequences or chemical fingerprints. The laboratory should document what the exercise evaluated and the limits of the conclusion.

Why two competent laboratories may report different numbers

Different results do not automatically mean one laboratory is dishonest or incompetent. The difference must be investigated in context.

The laboratories may not have tested equivalent samples

Botanical material can vary within a container or bulk lot. If samples were collected independently, sampling variation may exceed analytical variation. Even a divided sample can differ if the material was not homogenized before aliquots were prepared.

The methods may define the result differently

One laboratory may report on a dry-weight basis and another as received. One may report free compound while another calculation includes a salt or derivative. One may use a serving mass supplied by the client while another uses the measured content of an article.

Extraction and preparation can differ

Particle size, solvent composition, extraction time, mixing energy, temperature, filtration and dilution can affect recovery. For elements, digestion conditions and contamination control matter. For microbiology, test portion and enrichment conditions can change sensitivity.

Calibration and reference materials can differ

Different reference-material lots, purity assignments or calibration models can shift results. Metrological traceability helps connect measurements to stated references, but it does not make every method identical.

Reporting limits and rounding can create apparent disagreement

“Not detected” does not mean zero. It means the laboratory did not detect the analyte under the method and reporting conditions. A result below one laboratory’s limit of quantitation may be quantifiable at another. Rounding a value near a specification can also make two underlying results look more different—or more similar—than they are.

Every quantitative result has uncertainty

Measurement uncertainty describes a range associated with the result, not an admission that the number is meaningless. Two point estimates can differ while their uncertainty ranges overlap. Near a regulatory or internal limit, Kiody should use a predefined decision rule rather than treating the last displayed digit as absolute truth.

The product may have changed

Storage time, temperature, moisture exposure, light and packaging can affect some materials or analytes. If laboratories receive samples at different times or in different condition, a time-dependent change may contribute. Chain-of-custody records help evaluate this possibility.

A defensible split-sample comparison

When formal PT is unavailable for a specific kratom matrix and analyte, Kiody can ask a qualified quality professional to design a limited interlaboratory comparison. The purpose should be stated in advance: for example, to compare 7-OH quantitation in a botanical leaf matrix near the laboratory’s normal reporting range.

A useful plan should include:

1. A clearly identified source lot and product form.
2. A written homogenization and sampling procedure.
3. Matched aliquots of sufficient mass.
4. Containers that protect integrity and prevent contamination.
5. Chain-of-custody and shipping-condition records.
6. Laboratories selected before results are known.
7. Confirmation that both methods are suitable for the matrix and analyte.
8. Matching requested units and reporting basis.
9. A request for LOD, LOQ and measurement uncertainty where relevant.
10. A comparison rule defined before results arrive.
11. A plan for investigating disagreement.
12. Preservation of reserve material.

The comparison should not become “laboratory shopping.” Sending samples to successive laboratories until one produces a desired result undermines a defensible release decision. A conflict is information that requires investigation, not permission to discard the inconvenient result.

What an unsatisfactory proficiency result should trigger

Laboratories are run by people and instruments; occasional exceptions can occur. A mature quality system does not pretend otherwise. It responds in a controlled, transparent way.

Depending on the finding, a laboratory investigation may include:

• verifying sample receipt, storage and preparation records;
• reviewing calculations, dilution factors, units and data transfer;
• checking instrument performance, maintenance and calibration;
• confirming reference-standard identity, purity, expiration and preparation;
• reviewing blanks, spikes, recoveries, duplicates and control charts;
• evaluating chromatograms, spectra, plate observations or other raw data;
• assessing matrix interference, recovery and method scope;
• determining whether the error could affect customer reports;
• notifying affected clients when required;
• correcting reports through a controlled amendment process;
• revising or re-verifying the method;
• providing focused training when evidence identifies a training cause;
• documenting root cause and corrective and preventive action; and
• completing a follow-up challenge or effectiveness check.

The laboratory should not assume the analyst is the cause simply because an analyst generated the result. FDA’s laboratory policy notes that PT is ordinarily intended to assess the operation, not to evaluate an individual employee outside the laboratory’s normal operating design.

If a laboratory cannot identify the cause, it should still assess risk, implement appropriate containment and define how it will monitor effectiveness. “No root cause found” is not the same as “no problem existed.”

For Kiody, an unresolved competence concern should be escalated before relying on affected results for supplier approval, lot release or a legal-threshold decision. The appropriate response depends on the analyte, risk, result, product status and applicable law.

Twelve questions to ask about a laboratory’s PT evidence

1. Who operated the proficiency scheme or interlaboratory comparison? Confirm the provider’s identity and, when applicable, competence under ISO/IEC 17043.
2. Was this formal PT, a NIST quality-assurance exercise or another interlaboratory comparison? The description should match the program.
3. What was the round and date? A result from many years ago is not current evidence by itself.
4. Which analytes were actually evaluated? Do not rely on the name of a broad panel.
5. What matrix was used? Look for a botanical, food or finished-product matrix reasonably relevant to the customer sample.
6. What concentration range was challenged? Determine whether the exercise is relevant near the intended decision level.
7. What method and testing location produced the result? Match the evidence to the site and technical process used for Kiody.
8. How was the assigned value established? Ask whether it came from a reference value, formulation, expert laboratories or participant consensus.
9. What performance rule did the provider use? A score is hard to interpret without the scheme criteria.
10. Was performance satisfactory? A participation certificate alone may not answer this.
11. Were any exceptions investigated? Ask for an appropriate summary of root cause, impact assessment and completed corrective action without demanding confidential details unrelated to Kiody.
12. How often does the laboratory participate? Frequency should reflect the scope, risk, availability of programs and accreditation-body requirements.

A proposed Kiody laboratory proficiency record

For each outside laboratory used for botanical kratom testing, Kiody could maintain a controlled record containing:

1. Laboratory legal name.
2. Testing-site address.
3. Accreditation body and certificate number, if applicable.
4. Accreditation expiration or surveillance status.
5. Relevant accredited-scope entry.
6. Test category: identity, alkaloids, metals, microbiology, pesticides, mycotoxins, water activity or other.
7. Exact analyte or organism.
8. Matrix and product form.
9. Method or technique.
10. PT or interlaboratory-comparison provider.
11. Scheme and round identifier.
12. Participation date.
13. Concentration or challenge range.
14. Assigned-value basis.
15. Performance statistic or qualitative outcome.
16. Provider’s interpretation.
17. Any exception or unsatisfactory result.
18. Corrective-action summary and closure evidence.
19. Relevance assessment for Kiody’s products and decision levels.
20. Reviewer, approval date and next review date.

The record should distinguish evidence received from Kiody’s assessment. It should also identify gaps. “No suitable formal PT currently available” can be a truthful finding if the laboratory provides other competence evidence and a risk-based plan. Inventing or overstating a PT claim is not an acceptable substitute.

What customers can reasonably expect from Kiody

Customers should be able to match a certificate of analysis to the product lot and see which laboratory performed the work. Public-facing information should explain the test categories without implying that every possible hazard was tested or eliminated.

If Kiody discusses proficiency testing, the language should be precise. Examples of supportable statements, when records confirm them, include:

• “The laboratory participates in external proficiency testing for specified methods and analytes.”
• “Kiody reviews relevant proficiency and interlaboratory-comparison evidence as part of laboratory qualification.”
• “Program availability varies by analyte and matrix.”

Avoid claims such as “100% accurate,” “guaranteed safe,” “FDA-certified kratom laboratory” or “NIST-approved product.” Those statements overreach what PT, accreditation or NIST participation can establish.

Laboratory evidence is one part of a larger quality system. Supplier qualification, representative sampling, method suitability, lot traceability, specifications, controlled release, complaint review and recall readiness remain necessary.

Botanical leaf, concentrated 7-OH and current federal status

Ordinary botanical kratom leaf should not be treated as interchangeable with concentrated, enhanced, synthesized or semi-synthesized products. That distinction affects test-method suitability, concentration range, product review and legal analysis.

As of August 29, 2026, the federal action concerning 7-OH above specified thresholds remains a proposal, not an effective scheduling order. HHS extended the public-comment deadline to September 10, 2026. The proposal discusses criteria including 7-OH above 0.050% and a 1-milligram-per-article criterion in the circumstances described in the notice. Readers should consult the complete DEA proposal and HHS comment-period extension, rather than treating a proposed threshold as current federal law.

A separate DEA temporary order placed mitragynine pseudoindoxyl, MGM-15 and MGM-16 in Schedule I effective August 26, 2026, through August 26, 2028, unless the status is extended or changed through further legal action. That effective order is distinct from the pending 7-OH threshold proposal. See the effective DEA derivative order.

State and local restrictions may be stricter, may use different thresholds and may treat ordinary leaf and enhanced products differently. A laboratory result does not determine legal status by itself. Kiody’s nationwide botanical-leaf and 7-OH trackers should be consulted and legally reviewed before commerce decisions.

Kiody does not sell concentrated 7-OH.

Frequently asked questions

Does a proficiency-test result prove a laboratory is accurate?

It provides evidence of performance for a particular challenge at a particular time. It does not prove flawless performance for every analyte, matrix, method, concentration or future sample.

Is proficiency testing required for ISO/IEC 17025 accreditation?

Accreditation bodies generally use appropriate PT or other interlaboratory comparisons as evidence of competence under their policies. The exact participation plan depends on scope, risk and program availability. Review the laboratory’s accreditation scope and the accreditation body’s current requirements rather than assuming one universal frequency.

Is ISO/IEC 17043 the same as ISO/IEC 17025?

No. ISO/IEC 17043:2023 applies to organizations operating proficiency-testing schemes. ISO/IEC 17025 applies to testing and calibration laboratory competence. A laboratory can participate in a scheme run under ISO/IEC 17043 as part of its ISO/IEC 17025 quality system.

Does a participation certificate mean the laboratory passed?

Not necessarily. Some certificates show only that the laboratory participated. Ask for the provider’s performance evaluation or a defensible summary of the outcome.

Is a NIST quality-assurance program a proficiency test?

Not automatically. NIST expressly states that its dietary-supplement quality-assurance exercises are not strict pass/fail proficiency tests, even though they can help laboratories evaluate and improve measurement capability. Describe the program exactly as NIST describes it.

What is a z-score?

A z-score is one way to express the distance between a laboratory result and an assigned value relative to a standard deviation chosen for the exercise. The provider’s protocol determines how to interpret it. Do not apply cutoffs from one scheme to another without confirmation.

Can a laboratory pass PT and still issue a wrong customer result?

Yes. PT reduces uncertainty about competence but cannot prevent every sampling, handling, transcription, instrument or judgment error. Routine quality controls and report review remain necessary.

Why would two accredited laboratories disagree on a kratom result?

They may have received different subsamples, used different reporting bases, extraction procedures, calibration materials, limits or rounding rules. Measurement uncertainty and product change can also contribute. The discrepancy should be investigated before selecting a result.

Does proficiency for mitragynine prove proficiency for 7-OH?

No. Related analytes can behave differently in extraction, chromatography, detection and stability. Evidence should identify 7-OH specifically when the conclusion depends on 7-OH.

What if no kratom-specific PT program exists?

The laboratory can document other relevant evidence, such as comparable-matrix PT, suitable reference materials, method validation, fortified-sample studies and planned interlaboratory comparisons. The limitation should be transparent, and the evidence should be evaluated against the intended use.

Should Kiody reject a laboratory after one unsatisfactory PT result?

Not automatically. Kiody should evaluate the analyte, cause, impact on customer data, corrective action, follow-up evidence and accreditation status. Concealment, repeated unresolved failures or an inadequate impact assessment would raise more serious concerns than a well-investigated isolated exception.

Can PT prove that a kratom product is safe or legal?

No. PT evaluates laboratory performance. It does not approve a product, eliminate all risk, establish a medical benefit or override applicable law.

Does FDA approve kratom laboratories or products through PT?

No. FDA laboratory quality policies describe how FDA’s own regulatory laboratories use PT and interlaboratory comparisons; they do not confer FDA approval on a private kratom laboratory or product. FDA’s current kratom information should be reviewed for the agency’s current position.

Why does Kiody distinguish botanical leaf from concentrated 7-OH?

They differ in composition, analytical range, product-quality questions and legal treatment. A method or PT result suitable for ordinary leaf may not be suitable for a concentrated product. Kiody does not sell concentrated 7-OH.

Practical takeaway

Proficiency testing is valuable because it forces a laboratory to compare its ordinary measurement process with an external benchmark. It can expose bias or workflow problems that internal controls miss. But the phrase “proficiency tested” has little meaning without details.

For a defensible review, match the evidence to the exact analyte, matrix, method, concentration range, measurement basis and testing location. Confirm whether the document shows successful performance or only participation. Distinguish formal PT from a NIST quality-assurance exercise or an informal split-sample comparison. Then examine what the laboratory did when performance fell outside expectations.

The goal is not to find a laboratory that claims never to make a mistake. It is to select laboratories that can demonstrate competence, recognize exceptions, assess their impact and correct the underlying cause.

Primary and authoritative sources

1. National Institute of Standards and Technology, Dietary Supplement Laboratory Quality Assurance Program.
2. NIST, Food Nutrition and Safety Measurements Quality Assurance Program.
3. NIST, Quality Assurance Programs overview.
4. NIST Internal Report 8559, Dietary Supplement Laboratory Quality Assurance Program report, January 2025.
5. International Organization for Standardization, ISO/IEC 17043:2023, conformity assessment—general requirements for proficiency-testing providers.
6. ISO, ISO/IEC 17025 testing and calibration laboratories.
7. International Laboratory Accreditation Cooperation, ILAC policy-series publications, including ILAC P9:01/2024.
8. FDA, ORA-LAB.5.9: Proficiency Testing and Interlaboratory Comparisons.
9. FDA, Regulatory Testing Laboratory Manual of Quality Policies, July 2025.
10. FDA, FDA and Kratom.
11. Drug Enforcement Administration, Proposed temporary placement of 7-OH above a specified threshold, July 6, 2026.
12. Department of Health and Human Services, Extension of the 7-OH comment period, August 26, 2026.
13. Drug Enforcement Administration, Temporary placement of mitragynine pseudoindoxyl, MGM-15 and MGM-16 in Schedule I, August 26, 2026.