Clinical utility of chromogranin A in SDHx-related paragangliomas.

Background: Measurement of plasma/urinary catecholamine metabolites--especially normetanephrine (NMN)--represents a gold standard in biochemical detection of succinate dehydrogenase subunit B (SDHB) and D (SDHD)-related pheochromocytomas (PHEO) and paragangliomas (PGL). This study was designed to assess diagnostic utility of chromogranin A (CgA) alone or in combination with NMN in patients with PHEO/PGL related to mutations in SDHB and SDHD.

Methods: A retrospective study of SDHB and SDHD NIH patients' cohort, which included 41 patients with SDHB mutation-related PHEO/sPGL and 18 patients with either SDHD or SDHB mutation-related head and neck PGL (HNPGL) with both CgA and NMN measured at the time of diagnosis at NIH.

Results: In the SDHB group, CgA showed sensitivity of 73.2% and specificity of 95.9%, while for NMN they were 70.7% and 98.6%, respectively. Elevations in CgA and NMN were complementary in 92.7% of patients with proven tumors. Both tests performed well on receiver operating characteristic curve analysis. CgA levels were elevated in 76.9% of SDHB patients and in 80% of patients with metastatic disease and normal NMN levels. CgA values in patients with HNPGL were significantly lower than in patients with PHEO/sPGL.

Conclusions: CgA is a valuable complementary biomarker in work-up of SDHB-related PHEO/sPGL. In combination with plasma NMN, CgA further enhances tumor detection by 22.0% with minimal loss in specificity. Although non-specific for PHEO/PGL, CgA may well supplement plasma NMN to facilitate diagnostic evaluation of SDHB-related PHEO/sPGL, especially where the measurement of plasma metanephrines could otherwise be delayed by decreased availability or cost restriction.