[Chromogranin A in diagnosis of pheochromocytoma (comparative analysis)]

To study the prognostic value of determining Chromogranin A blood level in the diagnosis of PHEO.

We conducted a comparative analytical study of 157 patients with suspected PHEO, statistical analysis of 24-hour urinary metanephrine and normetanephrine excretion test was performed, as well as a blood test for CrA, in groups that included patients without PHEO, with primary tumor or its recurrence, confirmed according to MSCT and/or scintigraphy with MIBG and/or the clonidine suppression test.

The parameters of efficiency of these methods were calculated by groups and it was noted that the lowest sensitivity of the CrA determination method was observed in the group with recurrence of PHEO (43.8%), their exclusion from the entire sample didnt change specificity of the method and it remained at a high level (85.45%), though sensitivity significantly increased up to 87.1%. Sensitivity of determining 24-hour urinary metanephrine excretion also increased significantly up to 96.8%, with 98.2% of specificity. The correlation between diameter of the tumor and its secretory activity was identified: small with CrA level (rho 0.491) and strong with total level of methylated catecholamines (rho 0.765). False positive results were more often observed in patients present with other neuroendocrine tumors (37.5%), as well as those taking proton-pump inhibitors (43.75%). The sensitivity and specificity of CrA determining method in the group of patients with methanephrins elevated within gray zone appeared to be 50 and 86.1%, respectively.

A blood test for CrA can be recommended as a confirmatory test for diagnosing PHEO in cases of questionable methylated catecholamines indicators or in cases of suspected relapse of PHEO. The use of the test as a first-line method is only possible if there is no possibility to study methylated catecholamines. When interpreting CrA level, it is necessary to take into account the conditions that may cause false-positive results.