TITLE: Analytical Measureable Range (AMR) in Coagulation

PRINCIPLE:

AMR applies to hemostasis test methods that require a calibration and directly measure the concentration or activity of an analyte by employing enzyme immunoassay (EIA), immunoturbidity and chromogenic methods. The Innovance D-Dimer use immunoturbidity methodology and require a calibration. Clot based methods such as PT, PTT do not require a calibration. The AMR is the range of analyte values that a method can directly measure on the specimen without any dilution, concentration, or other pretreatment not part of the usual assay. At a minimum, three test specimens must have an actual result, which are near the low, midpoint and high values of the AMR. The high and low points should be within 10-15% of the AMR limits. The AMR is the range of analyte values for which this linear relationship has been established.

CLINICAL SIGNIFICANCE:

AMR validation is the process of confirming that the assay system will correctly recover the concentration or activity of the analyte over the AMR. Patient samples that have measured values that fall within the AMR of a method can be reported by the laboratory without further analytical steps. If the patient sample has a measured value that is outside the AMR, the value may be erroneous and the concentration of the analyte should be adjusted, usually by dilution, to bring it within the AMR.

Materials for AMR validation should have a matrix appropriate for the clinical specimens assayed by that method, and target values appropriate for the measurement system and that represent the quantitative relationship among the specimens. Materials may include, but are not limited to:

Linearity material of appropriate matrix, e.g. CAP Survey-based or other suitable linearity verification material.

Proficiency testing survey material or proficiency testing survey-validated material.

Previously tested unaltered patient specimens.

Previously tested patient specimens, altered by admixture with other specimens, dilution, spiking in known amounts of an analyte, or other technique.

Primary or secondary standards or reference materials with matrix characteristics and target values appropriate for the method.

Calibrators used to calibrate the analytical system that is from a different lot than the one used for the current calibration.

Control materials, if they adequately span the AMR and have method specific target values. The vendor of the Innovance system stated that the control material can be used for the AMR.

CALIBRATION/CALIBRATION VERIFICATION:

Calibration or Calibration Verification Criteria Include:

For detailed instructions on how to perform a calibration refer to the specific test SOP under the “calibration” section.

It is not necessary to independently verify the AMR if the calibration of an assay includes calibrators that span the full range of the AMR, with low, midpoint and high values (min of 3 points) and the system is calibrated at least every six months.

AMR verification is not required for clot-based coagulation tests where output is a unit of time rather than a measured analyte concentration.

The Calibrated tests performed in this laboratory include: Innovance D-Dimer. This calibrations is performed at a minimum:

Every 6 months

A change of reagent lots

If QC materials reflect an unusual trend or shift or outside of the laboratory’s acceptable limits, and other means of assessing and correcting unacceptable control values fail to identify and correct the problem.

After major preventive maintenance or a change of a critical instrument component

When recommended by the manufacturer

PROCEDURAL NOTES:

For D-Dimer’s it may not be relevant to report an actual numerical value, above a certain point. In this case, the result should be reported as “greater than” the value of the upper end of the AMR multiplied by the maximum allowable dilution of the analyzer.

See specific analyte SOP for details on the Analytical Measuring Range and the Reportable Ranges.

REFERENCE:

CAP Hematology and Coagulation Checklist, 09-25-2012; College of American Pathologists, pp.16-20. Standard #HEM.38009.

S: Laboratory Policies/Yorkville/Coagulation