Establishing and Verifying an Extended Measuring Interval Through Specimen Dilution and Spiking
|Publication Date:||1 August 2018|
This guideline provides procedures for establishing, validating, and verifying a dilution scheme to use for obtaining results for patient specimens with measurand concentrations or activity values above a measurement procedure's upper limit of quantitation (ULoQ). This guideline is intended to be used for measurement procedures that have an established AMI within which linearity, precision, and bias have been deemed acceptable. Guidance is provided on determining the appropriate diluent and dilution ratio for these specimens. This guideline also covers creating spiked samples for dilution recovery studies and using spiking studies to determine the suitability of a specimen type for dilution recovery studies. This guideline covers the measurement procedure after it meets design inputs and the resultant AMI has been established. The intended users of this guideline are IVD measuring system manufacturers and medical laboratory scientists, directors, and pathologists.
This guideline does not cover the process of developing a measurement procedure or determining the AMI or interval in which incremental results linearly correspond to increments in a measurand. Thus, it does not cover instituting a set of autonomous dilution steps or reflex examinations as part of the measurement procedure to create accurate results within the AMI. However, it is possible to test the performance of a measuring system's autonomous dilution steps using the protocols described in this guideline.