Introduction Chromogranin A (CgA) is used in the diagnosis and follow-up of patients with neuroendocrine tumours, whilst there is debate over the accuracy of CgA assays in gastric carcinoid type 1 (GC1). Clinical interpretation of CgA results may be affected by the heterogeneity between available assays. The commercial CgA assay, DAKO (DAKO, Denmark A/S, Glostrup, Denmark) is an ELISA which recognises a 23 kD C terminal fragment of CgA; the Imperial Supra-regional Assay Service radioimmunoassay (SAS Hammersmith Hospital, Imperial College, London) is a competitive radioimmunoassay raised against the whole pancreastatin molecule. Present study is aimed at comparing CgA-DAKO and CgA-SAS to determine their accuracy in the diagnosis of GC1.
Methods Patients with a confirmed diagnosis of GC1 and available plasma CgA measurements according to two different assays (SAS, DAKO) were included and 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 and 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 median CgA-DAKO significantly higher than median CgA-SAS: 3 vs. 1, T=0, p < 0.001. Sensitivity was 77% and 7.7% for CgA-DAKO and CgA-SAS, respectively.
Conclusion 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.
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Disclosure of Interest None Declared.