Working an EP15-style verification: serum creatinine

A hospital core laboratory is bringing up an FDA-cleared, unmodified enzymatic serum creatinine method on a new analyzer, used exactly as labeled. The intended use and unchanged status call for verification; the director first selects precision, bias, measuring-interval spot-check, and reference-interval fit as the relevant characteristics, then approves the protocol.

Low-level CV is 4.9% against the case limit of 5.0%; high-level CV is 3.9% against the case limit of 4.0%. Both pass and each is 0.1 percentage point from its case limit. Neither has priority without a stated clinical reason.

Bias against the assigned reference material is +2.7%, within the director’s case-specific ±5% limit. This limit was set before data review; it is not a default acceptance rule.

The 0.3–15.0 mg/dL measuring interval is spot-checked at three points. Recovery at each point is within the director’s case-specific ±6% limit. Those interval and recovery limits apply to this case only, not to every verification.

The reference interval is reviewed with 20 patient results under this case protocol. That count is a case design choice, not a universal requirement. The director reviews the completed study and approves patient testing with the protocol, raw data, and sign-off retained under local policy.

A passed verification is not the same as a comfortable one; note each tight margin in the study and give either level priority only when a stated clinical reason supports it.