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Immunochemistry

Immunochemistry

Rheumatoid Factor, Quantitative [Update]

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:

Interpretative ranges:
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.

Immunochemistry, Test Utilization

Helicobacter Antibody Testing

Effective March 1, 2016, Mayo Medical Laboratories will no longer perform any Helicobacter Antibody (IgG, IgM, or IgA) testing. The Mayo Clinic has determined that Helicobacter antibody testing has a poor predictive value, and also has poor clinical sensitivity and specificity. While a negative antibody result suggests the absence of prior Helicobacter exposure, a positive result is not predictive of active Helicobacter infection. Furthermore, since antibody levels may remain positive for years following resolution of infection serologic testing cannot be used to distinguish active from past infection or document eradication of Helicobacter infection following treatment. See the full text of a recent Mayo Medical Laboratories Communique article on Helicobacter testing methods for further information on the various available tests for Helicobacter infection.

Effective as of the above date, the Helicobacter pylori Antibody IgM and Helicobacter pylori Antibody IgA tests will no longer be available through the Spectrum Health Laboratory. The Helicobacter pylori Antibody IgG test (#8596), which is performed in house, will continue to be available until further notice, but may be subject to further review at a later time. Some third party payers are now considering Helicobacter antibody tests to be medically unnecessary and no longer reimbursing for them.

The Helicobacter pylori breath test (#3013, available from the Spectrum Health Laboratory) and the Helicobacter pylori Antigen, Stool test (#4307, available as a send out to Mayo Medical Laboratories) are now considered the primary recommended tests for the diagnostic evaluation of suspected Helicobacter infection. Refer to the linked Mayo diagnostic algorithm for further information on recommended approaches to Helicobacter pylori diagnostic testing.

Any questions concerning these changes in Helicobacter pylori testing may be directed to Dr. Richard Horvitz in the Pathology Department.

 

Immunochemistry, Referral/Sendouts

Chlamydia Antibody Testing Changes

The Spectrum Health Laboratory is no longer performing the Chlamydia Antibody Screen test (#8874). The reagent the Laboratory was using for this test is no longer available.

Specimens for Chlamydia antibody testing will now need to be sent to Mayo Medical Laboratories for their Chlamydia Serology panel (#37). This panel includes IgG and IgM antibodies to Chlamydia pneumoniae, Chlamydia trachomatis, and Chlamydia psittaci.

It should be noted that cross reactivity commonly occurs between these different Chlamydia species, especially for IgM antibodies. Infection by a particular organism generally yields IgG titers higher than those for non-infecting organisms.

Any questions concerning these changes may be directed to Sue Koekkoek, Medical Technologist in the Immunochemistry Department or to Dr. Richard Horvitz in the Pathology Department.