Calibration Verification and AMR Calculator

1. Type or paste one line per level: the material's assigned value, then what the analyzer reported. Run replicates if you can and put them all on the line (250 256 254); the tool averages them. Use at least three levels, from the bottom of the range to near its top. Five is common practice, and wide-range tests such as glucose read better with more.
2. Pick the limits your lab has written down: an analyte's CLIA proficiency testing limit, or your own percent and fixed amount. If you are judging the mean of replicates, you can apply a third of the limit.
3. Enter the reportable range you claim (the manufacturer's or your own) to see how much of it the passing levels cover.
4. Fill in the reason, date, instrument and lot, then print the record for the maintenance binder or copy the table into a spreadsheet.

Everything runs in this browser tab. Nothing you type is sent to AssayDeck or stored.

For each level, with the measured value taken as the mean of the results entered on its line:

difference = measured − assignedrecovery = measured ÷ assigned × 100 %allowed = the greater of (percent × assigned) and the fixed amount

A level is within limits when the size of the difference is no larger than the allowed amount; a result exactly on the limit counts as within. With “a third” picked, the allowed amount is divided by three. Recovery has no meaning at an assigned value of zero, so that level is judged on the difference alone.

The span the levels support runs from the lowest passing level to the highest passing level. If a level in the middle fails, there is no single span: the passing levels sit either side of a gap.

CLIA does not set a number. § 493.1255(b)(2)(i) asks for the lab's own criteria, “including the number, type, and concentration of the materials, as well as acceptable limits for calibration verification”. CMS's surveyor guidance, used at a CLIA inspection, says the same in practice: for calibrators, PT samples or assayed controls, “the laboratory must define acceptable limits for the difference between the measured value obtained, versus the actual concentration of the materials” (D5439).

Westgard's 2016 essay names CLIA's proficiency testing limits as one source of such limits, and two ways to apply them: the whole limit to single results, or about a third of it to the mean of replicates, because averaging removes most of the random error and what is left should be bias. He adds that “The laboratory Medical Director is ultimately responsible for defining the quality requirement and the limit for acceptable performance.”

So the PT option in the tool is a convenience, not a rule. It quotes the 2024 limits exactly, and you can type tighter ones from the manufacturer's insert or your own data instead. The sigma metric calculator shows how much of the same limit your imprecision already uses, and the QC statistics calculator gives the CV it needs.

CLIA defines reportable range as “the span of test result values over which the laboratory can establish or verify the accuracy of the instrument or test system measurement response” (§ 493.2). It enters twice:

• Once, before patient testing. An unmodified FDA-cleared or approved test system must show accuracy, precision and a reportable range comparable to the manufacturer's (§ 493.1253(b)(1)(i)(C)); a modified or in-house method must establish its own ((b)(2)(v)). CMS's guidance allows low and high calibration or control materials, or known samples of abnormal high and low values (D5421).
• Every 6 months after. Calibration verification uses “a minimal (or zero) value, a mid-point value, and a maximum value near the upper limit of the range to verify the laboratory's reportable range” (§ 493.1255(b)(2)(ii)). That is the span the tool reports.

AMR, the analytical measurement range, is the name the College of American Pathologists uses; its calibration verification and linearity program covers “scheduled calibration verification and verification of the analytical measurement range” and points to § 493.1255. In CLIA's own words it is the reportable range.

A patient result above the range has three ways out, per CMS: report it as greater than the highest limit, re-assay a diluted specimen and report the calculated result, or send it to a reference laboratory (D5421).

Calibration verification is due at least once every 6 months, and whenever:

• a complete change of reagents is introduced, unless the lab shows the new lot does not affect the reporting range or controls ((b)(3)(i));
• there is “major preventive maintenance or replacement of critical parts that may influence test performance” ((ii));
• controls show “an unusual trend or shift” or fall outside the lab's limits and other means fail to correct it ((iii));
• the lab's own schedule asks for it more often ((iv)).

If it fails, § 493.1255(a)(3) requires calibration “whenever calibration verification fails to meet the laboratory's acceptable limits”. CMS's brochure adds that if problems remain after recalibration the lab must take and document corrective action, and that calibration verification records are kept for two years.

CMS's interpretive guidelines (D5439) treat the requirement as met, or not needed, when:

• the calibration itself uses 3 or more levels including a low, mid and high value at least every 6 months;
• an automated cell counter is run to the manufacturer's instructions with 2 levels of controls each day of testing (not centrifugal hematology systems);
• an automated chemistry analyzer runs three NIST-traceable control levels, lowest, mid and highest available, more than once each day of testing;
• the instrument is factory calibrated, or the test is non-quantitative, such as prothrombin time and activated clotting time.

Routine daily controls do not count: “Control activities routinely used to satisfy the requirement for §493.1256 do not satisfy the calibration verification requirements.” The rules are the same at every non-waived complexity; waived tests need it only if the manufacturer says so. See how often to run QC for the daily side, and the CLIA inspection checklist for where a surveyor looks.