Clinical Diagnostic Laboratories: CLIA and ISO 15189
A laboratory that tests human specimens to diagnose, prevent or treat disease, or to assess an individual patient’s health, works under a different regime from a GMP quality-control or GLP laboratory. In the US, the Clinical Laboratory Improvement Amendments and 42 CFR Part 493 require a certificate matched to the complexity of the testing, proficiency testing and inspection. Internationally, ISO 15189 sets requirements for quality and competence that accreditation bodies assess. The patient result, not a batch release, is what the system protects.
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A topic explainer is SPEQ’s synthesis of what a practice involves, cited to the standards that govern it. It does not reproduce their text, and it does not determine which of them apply to your product or process.
Who CLIA Covers
Under 42 CFR 493.3, a laboratory must hold a current CLIA certificate applicable to the examinations it performs — a certificate of waiver, registration certificate, certificate of compliance, certificate for provider-performed microscopy (PPM) procedures or certificate of accreditation — or be CLIA-exempt. The rules do not apply to forensic testing, to research laboratories that do not report patient-specific results for diagnosis, prevention, treatment or health assessment, or to SAMHSA-certified drug testing that meets SAMHSA requirements.
That research exception is narrow. A clinical-trial or biomarker laboratory that returns individual results used for patient care has moved inside CLIA, whatever its sponsor calls the study.
Test Complexity and Certificates
Tests are categorised as waived, moderate complexity (including the PPM subcategory) or high complexity (493.5). Waived tests are simple examinations that are cleared for home use, use methods so simple and accurate that erroneous results are negligibly likely, or pose no reasonable risk of harm if performed incorrectly (493.15(b)). A laboratory with a certificate of waiver may perform only waived tests.
Laboratories doing moderate or high complexity testing hold a certificate of compliance, inspected by CMS or its agent, or a certificate of accreditation from a CMS-approved accreditation organisation. Inspections may be biennial or as frequent as CMS considers necessary, and their nature depends on the laboratory’s compliance history (493.1777(b)).
Proficiency Testing
A laboratory doing non-waived testing enrolls in an HHS-approved proficiency testing program for each specialty and subspecialty it is certified for, and tests PT samples in the same manner as patient specimens (493.801). Where its procedure would refer a patient specimen to another laboratory, it tests the PT sample only up to that point.
Referring a PT sample to another laboratory for analysis is treated severely: a laboratory found to have intentionally referred one may have its certification revoked for at least a year. PT records are kept for at least two years from the PT event.
Laboratory Developed Tests
FDA’s May 2024 final rule would have phased out its general enforcement discretion for most laboratory developed tests and regulated them as devices. On 31 March 2025 a federal district court vacated that rule, and on 19 September 2025 FDA issued a final rule restoring the text of 21 CFR 809.3 as it stood before. Laboratory developed tests therefore remain governed by CLIA, with FDA’s position as set out on its LDT page.
Commercial in vitro diagnostic test kits remain medical devices regulated by FDA. A laboratory that modifies an FDA-cleared test, or builds its own, carries the validation burden under CLIA itself.
ISO 15189 Accreditation
ISO 15189:2022, the fourth edition published in December 2022, specifies requirements for quality and competence in medical laboratories. It is used by laboratories to build their management systems and by laboratory users, regulators and accreditation bodies to confirm competence. It revised the 2012 edition and absorbed ISO 22870, so point-of-care testing now falls within the same standard.
The standard covers the whole testing pathway: pre-examination steps such as requests, collection and transport; examination procedures, their validation or verification, and quality control; and post-examination review, reporting and retention. Risk management and personnel competence run through it. In the US, ISO 15189 accreditation does not by itself satisfy CLIA; the laboratory still needs the CLIA certificate that matches its testing.
FREQUENTLY ASKED
Does CLIA apply to a research laboratory?
Not if it tests human specimens but does not report patient-specific results for the diagnosis, prevention or treatment of disease or the assessment of an individual’s health (42 CFR 493.3(b)(2)). Once individual results are reported for patient care, CLIA applies.
What makes a test CLIA-waived?
A waived test is a simple examination that is cleared by FDA for home use, uses a method so simple and accurate that an erroneous result is negligibly likely, or poses no reasonable risk of harm to the patient if performed incorrectly (493.15(b)).
Is FDA’s laboratory developed test rule in force?
No. A federal district court vacated it on 31 March 2025, and FDA’s final rule of 19 September 2025 restored 21 CFR 809.3 to its earlier text.
Does ISO 15189:2022 cover point-of-care testing?
Yes. The 2022 edition states that it is also applicable to point-of-care testing, and it revised ISO 22870, the former point-of-care standard, along with the 2012 edition of ISO 15189.
The inspection-readiness playbook for this topic
PUT THIS PLAYBOOK TO WORK
- HOW-TO GUIDEHow to Implement ISO 15189 in a Medical Laboratory →Build a diagnostic laboratory system around the patient the result belongs to.
- TEMPLATEISO 15189 Implementation Plan →
- HOW-TO GUIDEHow to Run a Clinical Diagnostic Laboratory Under CLIA →Operate under the US federal regime that applies to the testing site itself.
- TEMPLATECLIA Compliance Record →
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