Imperial Collage Healthcare
02 February

Imperial Syphilis testing protocol update

Additional testing to confirm equivocal syphilis results
A Public Health England (PHE) risk alert (Reference: RA15.041) has highlighted that the Abbott Architect syphilis TP assay (currently in use by the Infection & Immunity laboratory at Imperial College Healthcare Pathology) may falsely interpret some results as negative if a “grey zone” is not used for their interpretation. Hence, laboratories using this assay should utilise a grey zone within which results are considered “equivocal” and require further testing.
Based on this recommendation, our laboratory has introduced a grey zone and all samples within it will have additional testing.

There will be minimal impact on our turn-around-time. However, you will see two new additional reports (in addition to the usual POSITIVE and NEGATIVE results) as follow:
1. Initial result was EQUIVOCAL but confirmatory test is NEGATIVE
2. Initial result was EQUIVOCAL and confirmatory test is POSITIVE

Please note that all positive samples will be tested for TPPA and RPR and all discrepant antenatal samples will be referred to the Reference laboratory as usual.

If you require any further clarification, please do not hesitate to contact:
Dr Giovanni Satta, Consultant in Medical Microbiology/Infectious Diseases

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