PB0968 - Evaluation of an automated Protein C antigen assay

Background: Inherited or acquired Protein C deficiencies are associated with increased risk of VTE. Protein C antigen levels are used to support Protein C activity results in the diagnosis of inherited Protein C deficiency and the differentiation of Type I (quantitative) from Type II (qualitative) deficiency. The Liaphen Protein C antigen (Hyphen Biomed, France) is an automated assay that offers the potential to reduce turnaround times as an alternative to our ELISA method which is both time-consuming and labour intensive.

Aims: To evaluate the performance of the Liaphen Protein C antigen assay on the Sysmex CN-6000 (Sysmex, UK) and assess its suitability as alternative to our current ELISA, in house method utilising paired antibody (Affinity Biologic, USA) .

Methods: 107 samples were tested against stored calibration curves with results compared to our in house Protein C antigen test. Reproducibility was assessed with two levels of inhouse produced QC material over 13 sample runs. Repeatability was assessed with 10 repeats of the same patient sample. 18 sample on patients receiving Warfarin were tested to determine the assay performs in the presence of VKA.

Results: The assay performed strongly when compared to the ELISA test. Mean values of the two data sets was 0.58 IU/mL for ELISA and 0.56 IU/mL for the automated assay the R value of the two data sets was 0.95 with an R2 of 0.91. CV for repeatability was 2.5% and reproducibility was also 2.5%, superior to the CV of the ELISA , repeatability 4.2% and reproducibility 7.3%. Three consecutive calibration curves demonstrated R2 value of >0.997.

Conclusion(s): The Liaphen Protein C antigen shows strong correlation with results produced by our established ELISA method and is suitable alternative to more labour intensive methods.