To enable conversion between screening systems e.g. for comparison of screening test results between:
- QA programs
- Test result. This can be expressed either as positive/negative with an indication of the cutoff limit or SI units of measure, including whether units relate to serum or blood volumes . Consideration should be given to the accuracy of the test when determining the number of significant figures to report
- Punch size and equivalent serum or blood volume (include hematocrit percentage used in conversion if appropriate).
- Type of filter paper used, including Lot number and manufacturer.
- Origin and characteristics of material used to prepare dose-response curve (include traceability to international reference material if possible/appropriate).
- Assay methodology:
- Storage of Guthrie cards prior to analysis:
a. Assay type (e.g. bacterial inhibition assay, RIA)
b. Dose indicator
c. Source of reagents specific to the assay
d. Cross reactivity with specificity (especially of structural analogues which might be expected in the biological matrix)
e. Time and temperature of any incubation
f. Data reduction method used
Assay methodology can be replaced by a referenced method and a note of any changes made to the referenced method.