Direct comparison
ISO 15189 vs CLIA: Lab Accreditation Compared
ISO 15189 (voluntary global standard) vs CLIA (mandatory US law): what each covers, how CAP deemed status fits, and what to verify when vetting a lab vendor.
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How do ISO 15189, CLIA compare side by side?
The table below compares ISO 15189, CLIA across 9 procurement-relevant dimensions, from what it is through typical procurement relevance.
Side-by-side comparison
| Dimension | ISO 15189 | CLIA |
|---|---|---|
| What it is | A voluntary international standard (“Medical laboratories — Requirements for quality and competence”), current edition ISO 15189:2022, published by ISO/TC 212. | A mandatory US federal regulation (Clinical Laboratory Improvement Amendments of 1988), implemented at 42 CFR Part 493. |
| Administered / issued by | National accreditation bodies (e.g., A2LA, ANAB, CAP’s ISO 15189-based program in the US; UKAS in the UK), based on the ISO text. | CMS (certification/survey), FDA (test-complexity categorization), CDC/CLIAC (scientific/technical guidance). |
| Legal status | Voluntary — no jurisdiction requires it by default, though some countries’ regulators or contracts may reference it. | Mandatory for any US laboratory testing human specimens and reporting patient-specific clinical results (genuine non-reporting research labs are exempt under 42 CFR 493.3). |
| Geographic reach | Global — used by national accreditation bodies worldwide; ILAC MRA (consolidated into the Global ACI MRA on 1 January 2026; existing accreditations remain recognised) signatory bodies’ accreditation carries cross-border recognition. | US federal jurisdiction only. |
| What is assessed | Whole-pathway quality management system plus technical competence for a defined scope of medical examinations. | Personnel qualifications, QC/QA, and proficiency testing performance, organized around the certificate type and test complexity. |
| Recognition mechanism | Accreditation with a defined scope, issued after on-site assessment against the standard. | A CLIA certificate (five types); may be obtained via direct state survey or via a CMS-deemed accrediting organization. |
| Relationship to CAP | CAP offers a separate, ISO 15189-based accreditation program — a distinct, voluntary credential. | CAP’s main Laboratory Accreditation Program is a CMS-deemed route that satisfies CLIA — a different CAP program from its ISO 15189 track. |
| Proficiency testing | Requires participation in proficiency testing or another interlaboratory comparison as part of the quality system. | Mandates enrollment and specific performance thresholds for regulated analytes under 42 CFR Part 493, Subpart H. |
| Typical procurement relevance | Verify when qualifying a non-US lab, a multi-country trial’s central/local labs, or as an added quality differentiator. | Verify as a baseline, non-negotiable requirement for any US lab reporting clinical patient results. |
Common questions
Common questions about ISO 15189 vs CLIA
Can ISO 15189 accreditation replace a CLIA certificate for a US clinical lab?
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No. ISO 15189 accreditation on its own is not one of CMS’s CLIA-deeming mechanisms. A US laboratory testing human specimens and reporting patient-specific clinical results still needs a CLIA certificate, obtained either through direct state survey or through a CMS-deemed accrediting organization.
Does CAP accreditation satisfy both ISO 15189 and CLIA?
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Not automatically, and not through one program. CAP’s main Laboratory Accreditation Program provides CMS-deemed status that satisfies CLIA. CAP separately offers an ISO 15189-based accreditation program, a distinct voluntary credential. A lab can hold either, both, or neither — confirm which specific CAP program a vendor participates in.
Is ISO 15189 required for laboratories outside the United States?
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Not universally by law in every country, but it is the standard most national accreditation bodies use as their benchmark for medical laboratory accreditation, and it is often expected in practice for cross-border trial work and reference-lab partnerships.
What should a procurement officer request when qualifying a reference lab?
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The lab’s current CLIA certificate number and type (or the CMS-deemed accrediting organization’s name and status), and, if relevant, its ISO 15189 accreditation body and scope of accreditation, plus current proficiency testing enrollment and any open corrective actions from its most recent survey or assessment.
Going deeper
