Endocrine Abstracts

Background: Chromogranin A is an acidic 48 kDa glycoprotein originating from the chromaffin granules of most neuroendocrine cell types. In health chromogranin A is released as a pro-hormone together with other peptide hormones in response to stimulation. In disease larger quantities of Chromogranin A are produced by neuroendocrine derived tumours thus allowing its use as a tumour marker. Due to the different clinical scenarios for measuring Chromogranin A requesting practices within Scotland vary considerably. Currently labs in Scotland either send samples for a single chromogranin A measurement in London, Manchester or Sheffield or a combined gut hormone profile in London.

Method: The CisBio ELISA chromogranin A method was validated to assess linearity, lower limit of sensitivity, imprecision and accuracy. Paired serum samples were collected from 100 patients who were also having a full gut hormone profile measured at Charing Cross in London. The serum samples were analysed using the CisBio ELISA chromogranin A method and compared to the results from Charing Cross. External quality control samples (n=20) from the IMMQAS chromogranin A pilot scheme were analysed and compared to both the method mean and other assays.

Results: Validation proved the assay had a sensitivity of 15 ng/L, samples diluted linearly, the imprecision was ≤10% across the linear range and the assay showed no consistent bias when compared to the NEQAS method mean. The patient comparison with the Charing Cross assay showed 78% consensus.

Conclusion: The CisBio chromogranin A ELISA has performed well analytically and has the sensitivity, linear range and precision required for a tumour marker assay. Comparison data shows the assay is of equal clinical utility to the assay offered by the main referral laboratory. Therefore, the CisBio chromogranin A assay has the potential to improve comparability, cost effectiveness and sample turnaround times for patients in Scotland.