Endocrine Abstracts

Background: Chromogranin A (CgA) is essential for the formation of secretory granules and sequestration of hormones in neuroendocrine cells. Measurement of CgA levels is included in the diagnostic procedure of neuroendocrine tumors and pheochromocytoma. The aim of this study was to assess the reliability of the Kryptor assay for CgA measurement.

Methods: Imprecision of the Kryptor CgA assay was determined with two levels of CgA concentration. Reference values for the Kryptor CgA (B.R.A.H.M.S GmbH, Thermo Scientific, Germany) assay were obtained from thirty five healthy subjects. Method comparison was performed with our routine CgA assay (Dako, Glostrup, Denmark) with eighty five patients’ samples.

Results: Between run imprecision (n=6) performed with quality controls materials for the CgA assay were 4.0% and 3.4% for mean concentrations of 98 ng/ml and 481 ng/ml, respectively. CgA levels measured with the Kryptor were significantly correlated with CgA levels obtained with our routine assay (r=0.96, P<0.0001).The agreement between the two methods was very good (weighted κ coefficient: 0.84). However, seven cases were discrepant between the two methods. For low concentrations (below 23 UI/l with the routine assay), Passing and Bablok regression analysis showed a slope of 5.36 and an intercept of 37.38 (n=40). Bland and Altman plot evidenced a positive bias (mean difference of 22.1) with higher values for Kryptor assay. For high concentrations (above 23 UI/l with the routine assay), Passing and Bablok regression analysis showed a slope of 3.49 and an intercept of 10.76 (n=36). Bland and Altman plot evidenced a positive bias (mean difference of 526.4) with higher values for Kryptor assay.

Conclusions: Our study showed that the Kryptor assay is reliable for chromogranin-A measurement. However, CgA assays are not commutable and laboratories must inform the physicians of the characteristics of potential new routine assay.

Declaration of interest: I fully declare a conflict of interest. Details below.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.