As of June 21, 2016 the SHRL Immunochemistry department changed methods for Rheumatoid Factor, Quantitative (Test #8522, Epic #LAB206). In terms of interpretations, both methods compared well; however, the actual numerical results between methods are not interchangeable and a reference range change was required. The new ranges are listed below:
Negative : <3.5 IU/ml
Equivocal: 3.5-5.0 IU/ml
Positive: >5.0 IU/ml
This is only in effect at the Spectrum Health Regional Laboratory; Spectrum Health Gerber Laboratory is still performing using the immunoturbidimetric assay.