Variation in Chromogranin A Assays in Gastric Carcinoid TYPE 1

Abstract

AIM: Chromogranin A (CgA) is used in the diagnosis and follow-up of patients with neuroendocrine tumours. Clinical interpretation of CgA results may be affected by the heterogeneity between available assays. There is debate over the accuracy of CgA assays in gastric carcinoid type 1 (GC1). Herein, we compare two different CgA assays, the commercial CgA assay, DAKO (DAKO, Denmark A/S, Glostrup, Denmark) and the Imperial Supra-regional Assay Service radioimmunoassay (SAS Hammersmith Hospital, Imperial College, London) to determine their accuracy in the diagnosis of GC1. methods: Patients diagnosed with GC1 and available plasma CgA measurements according to two different assays (SAS and DAKO) were retrospectively reviewed. CgA values were ranked in 4 groups: (1) normal values; (2) increase<2 Upper Limit of Normal (ULN); (3) increase between 2-5 ULN; (4) increase>5 ULN. Results: 26 patients (17 female, 9 male), mean age 55 years±11.75, were identified. At diagnosis, median CgA-DAKO were significantly higher than median CgA-SAS (81, normal range <27 IU/L versus 34.5 pmol/L, normal range <60 pmol/L, T=35.5, p< 0.001). When ranking the data, the results confirmed that median CgA-DAKO was significantly more accurate than median CgA-SAS: 3 versus 1, T=0, p<0.001. Sensitivity was 77% and 7.7% for CgA-DAKO and CgA-SAS, respectively. Pearson correlation between gastrin levels and both CgA-DAKO and CgA-SAS were non-significant [r(26)= 0.08 and r(26)= 0.2, p> 0.05 for CgA-DAKO and CgA-SAS, respectively]. Conclusions: CgA-DAKO shows a better sensitivity than CgA-SAS for the diagnosis of GC1. Accurate diagnostic biomarkers may identify those patients who may benefit from a closer endoscopic follow-up in cases of raised neuroendocrine markers. Further prospective studies are needed highlighting the difference in diagnostic sensitivity between assays.