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A comparison of three chromogranin A assays in patients with neuroendocrine tumours.

BACKGROUND AND AIMS
Chromogranin A (CgA) is the most important general tumour marker used in the diagnosis and follow-up of patients with neuroendocrine tumours (NET). Chromogranin A assays may have different sensitivities, which is of importance for the clinical diagnosis and handling of NET patients. The aim of this study was to compare the clinical sensitivities of three different CgA assays in NET patients.


METHODS
We measured CgA level in 42 NET patients (male/female: 23/19, median age: 63 years, range 29-85 years). Twenty-five patients had liver metastases, eight had local disease, and nine were disease free after surgery. We studied an in-house RIA: RH RIA assay (Rigshospitalet, Copenhagen, Denmark); NEOLISATM (Euro Diagnostica, Malmö, Sweden) and EURIA CgA RIA (Euro Diagnostica, Malmö, Sweden).


RESULTS
The RH RIA assay showed a clinical sensitivity of 97%, while the NEOLISA and EURIA assays both showed similar clinical sensitivities of 79%. Patients with liver metastases had significantly higher CgA levels compared to disease free patients by all three assays (P<0.001), but only the RH RIA assay was able to discriminate between patients with liver metastases and with regional disease (P<0.01).


CONCLUSION
Chromogranin A measurements are significantly assay-dependent and caution should be applied in the interpretation of CgA measurement for assessment of NET status. The in-house RH RIA assay was better at predicting NET status than the NEOLISA and EURIA assays.