Written and maintained by CASRAI Editorial Board
Last updated
“CAP proficiency testing” refers to two related but distinct things: the College of American Pathologists’ own PT/EQA program (commonly called CAP Surveys), which is a CMS-approved proficiency testing provider that any laboratory can enroll in, and the proficiency testing requirement built into CAP’s Laboratory Accreditation Program, which every CAP-accredited laboratory must satisfy whether or not it uses CAP’s own Surveys as its provider. Confusing the two is common and matters practically: a laboratory can buy CAP Surveys kits without being CAP-accredited at all, and a CAP-accredited laboratory can (for regulated analytes) satisfy its proficiency testing obligation through a different CMS-approved provider entirely. This guide separates the two, explains how each connects to the underlying CLIA requirement, and covers enrollment, scoring, and what happens after an unsuccessful result.
For the general mechanics of proficiency testing and external quality assessment (EQA) — how PT schemes are structured under ISO/IEC 17043, how z-scores are calculated, and the specific CLIA regulation (42 CFR Part 493, Subpart H) that makes PT mandatory — see our companion guide, Proficiency Testing & External Quality Assessment (EQA) for Accredited Labs. This page focuses specifically on how CAP implements and requires PT/EQA.
What CAP Is, and Why Its Name Shows Up on Both Sides of PT
The College of American Pathologists (CAP) is a physician-led medical society that plays two separate roles in US clinical laboratory quality:
- Accreditor. CAP operates the CAP Laboratory Accreditation Program, which uses discipline-specific inspection checklists to accredit clinical laboratories. CAP has held CMS deeming authority under the Clinical Laboratory Improvement Amendments (CLIA) for decades, meaning a laboratory that maintains CAP accreditation is treated by CMS as meeting the equivalent CLIA requirements without a separate federal inspection — the same “deemed” relationship covered for other accreditors in our CLIA certification guide.
- PT/EQA provider. Separately, CAP runs CAP Surveys, one of the longer-running CMS-approved proficiency testing programs, spanning roughly 16 disciplines across clinical chemistry, hematology, microbiology, immunohematology/blood banking, anatomic pathology, and molecular pathology, among others. Any laboratory — CAP-accredited or not — can enroll and purchase CAP Surveys PT kits for the analytes it tests.
Because both roles share the CAP name, “CAP proficiency testing” in practice usually means one of: enrolling in CAP Surveys as a PT provider, or satisfying the PT/EQA condition that CAP’s own accreditation checklists impose on an accredited laboratory. The next section covers both.
How CAP Proficiency Testing Connects to CLIA and Accreditation
The underlying CLIA mandate
CLIA requires every laboratory holding a certificate of compliance or accreditation to enroll in a CMS-approved PT program for the specific “regulated” specialties, subspecialties, and analytes listed in 42 CFR Part 493, Subpart H, and to test the PT samples exactly as it would a patient specimen. This obligation exists independent of which accreditor a laboratory uses — it is a direct CLIA requirement, not something CAP invented. Our PT/EQA guide covers the regulatory mechanics, scoring conventions, and the prohibition on PT referral in detail.
What CAP’s own accreditation checklists add
CLIA’s PT mandate only covers the “regulated” analyte list. For everything else — the large majority of tests a modern clinical laboratory runs, since CLIA’s regulated-analyte list has not kept pace with the growth of clinical testing — a laboratory still has to demonstrate ongoing test accuracy. The CAP Laboratory Accreditation Program’s checklists require CAP-accredited laboratories to verify performance on non-regulated tests too, at least twice a year, using either a formal PT/EQA scheme (CAP’s own or another provider’s) or an alternative performance assessment method where no formal PT program exists for that analyte. This checklist requirement is the reason a laboratory can be fully CLIA-compliant on paper and still fail a CAP accreditation inspection over its non-regulated-analyte quality assurance — CAP’s bar is broader than the bare CLIA regulation.
Alternative Performance Assessment (APA)
For analytes with no CMS-approved PT scheme available — common for newer, more specialized, or lower-volume tests — CAP-accredited laboratories still have to verify accuracy at least twice a year through some other defensible method. CAP supports this through its Sample Exchange Registry for Alternative Assessment, which connects laboratories so they can split and compare patient samples with each other, alongside other CAP-recognized options such as testing split samples against a reference method, comparing results against a second validated method within the same laboratory, or participating in a relevant clinical trial or research collaborative that generates comparable data. The point of APA is the same as formal PT — an independent, outcome-based check that the laboratory’s real-world results are accurate — just applied where no third-party PT provider covers that specific analyte yet.
Enrolling in and Running CAP Surveys
The operational workflow for CAP Surveys follows the same general pattern as any PT/EQA scheme (see the companion guide for the underlying mechanics), with CAP-specific administration:
- Select the Surveys programs that match your test menu. CAP Surveys is organized by discipline and analyte, so a laboratory enrolls only in the specific programs that cover the tests it actually performs.
- Receive and test PT samples on the normal schedule. Samples are analyzed using the laboratory’s routine method, routine staff, and routine equipment — not special handling — consistent with the CLIA requirement covered in the companion guide.
- Submit results by the stated deadline, typically through CAP’s online laboratory-management platform, e-LAB Solutions Suite, which is also where accredited laboratories manage checklists, corrective action documentation, and other accreditation-related workflow.
- Receive graded performance reports. CAP evaluates submitted results against the assigned/consensus value for the analyte and returns individual laboratory scores alongside participant-group summary statistics, following the general scoring conventions (including z-scores for quantitative disciplines) described in our companion guide.
Unsuccessful Performance: What CAP Requires
An unsuccessful (failing or “unacceptable”) PT result on a CAP Survey is not, by itself, an accreditation-ending event, but CAP’s accreditation checklists require a documented response, generally including:
- A root cause investigation into why the result was unsuccessful — instrument, reagent, method, or operator issue.
- A corrective action plan addressing the identified cause, documented in the laboratory’s quality records.
- Verification that the corrective action worked, typically evidenced by satisfactory performance on the next testing event for that analyte.
What escalates the situation is a pattern, not a single miss: CLIA and CAP both treat repeated unsuccessful performance on the same analyte, or evidence that a laboratory reported patient results it knew or should have known were unreliable, far more seriously than an isolated unsuccessful event with a documented, resolved root cause. As with any PT scheme, sending a PT sample to another laboratory for confirmation or analysis (PT referral) is a distinct and serious violation, regardless of the underlying performance issue — it is prohibited even when the laboratory’s intent is simply to double-check a result.
CAP Surveys, Other CMS-Approved PT Programs, and CAP Accreditation: Not the Same Choice
| Question | Answer |
|---|---|
| Do I have to be CAP-accredited to buy CAP Surveys? | No. Any laboratory can enroll in CAP Surveys as its PT provider, independent of which body (if any) accredits the laboratory. |
| Does CAP accreditation require using CAP Surveys specifically? | No, for regulated analytes. A CAP-accredited laboratory can use any CMS-approved PT provider for its regulated-analyte testing; CAP’s checklists require participation in a compliant program, not participation in CAP’s own program. |
| Does CAP accreditation add requirements beyond CLIA’s PT mandate? | Yes. CAP’s checklists extend the twice-yearly verification expectation to non-regulated analytes via PT/EQA or alternative performance assessment, which bare CLIA regulation does not require. |
| Is CAP the only CMS-approved PT provider? | No. CMS approves multiple PT providers; CAP Surveys is one of the longer-established and broadest in scope, but laboratories are free to choose among approved providers for regulated analytes. |
Frequently Asked Questions
What is CAP laboratory accreditation?
CAP laboratory accreditation is a voluntary, inspection-based accreditation granted by the College of American Pathologists to clinical laboratories that meet its discipline-specific checklists, covering personnel, quality management, and testing accuracy (including PT/EQA participation). Because CAP holds CMS deeming authority, a CAP-accredited laboratory is treated as meeting the equivalent CLIA requirements without a separate federal inspection. See our CLIA certification guide for how deemed-status accreditation fits into the broader CLIA certificate framework.
What does it mean for a lab to be a “CAP accreditation lab”?
It means the laboratory currently holds active CAP accreditation — it has passed a CAP on-site (or hybrid) inspection against the relevant checklists and maintains ongoing compliance, including PT/EQA or alternative performance assessment, between inspection cycles.
Is CAP proficiency testing mandatory?
Participation in some form of PT/EQA is mandatory for regulated analytes under CLIA regardless of accreditor, and CAP’s own checklists extend that expectation to non-regulated analytes for laboratories that hold CAP accreditation. Whether it has to be specifically CAP Surveys, versus another CMS-approved provider, is the laboratory’s choice.
What happens if a laboratory fails a CAP proficiency test?
The laboratory has to investigate the root cause, document and carry out a corrective action, and demonstrate the issue is resolved — typically through satisfactory performance on the next testing event. A single unsuccessful result with a documented resolution is a normal, expected part of running a testing program; a repeated or unaddressed pattern is what puts accreditation status at risk.
How is CAP Surveys different from ISO/IEC 17043-based PT schemes generally?
They are not actually different categories — CMS-approved PT providers, including CAP Surveys, operate against the same general statistical and quality principles that ISO/IEC 17043 codifies internationally. See our ISO/IEC 17025 guide for how laboratory-competence accreditation (a related but separate standard from the PT-provider standard, ISO/IEC 17043) fits alongside CLIA/CAP accreditation for laboratories that also need testing-and-calibration-lab accreditation.
