Endocrine Abstracts

Introduction: Phaeochromocytomas and paragangliomas (PPGL) are rare but important causes of hypertension requiring a different treatment paradigm to essential hypertension. Despite this, national guidelines on PPGL screening in hypertension are vague. We evaluated the yield of PPGL screening in a regional hypertension service.

Methods: All patients who had undergone a 24-hour urine collection for metanephrines from the Hypertension Clinic at Sheffield Teaching Hospitals NHS Foundation Trust between 1/1/23 and 31/12/24 inclusive were identified. Biochemical and clinical data were extracted from the electronic patient record. Metanephrine and normetanephrine were analysed by high-performance liquid chromatography with the use of in house derived reference intervals.

Results: 222 patients (126 male, median age 37 years) were included in the analysis. Indications for testing were young-onset hypertension (n = 173, 78.0%), resistant hypertension (n = 31, 14.0%), or both (n = 18, 8.1%). 21 results (9.5%) were above the above the upper limit of the reference interval (metanephrine 1, normetanephrine 20); 7 (3.2%) of which were also above the ‘borderline’ reference interval (metanephrine 1, normetanephrine 6). No patients were ultimately diagnosed with a PPGL. Of the 21 abnormal results, 17 were attributable to medications and/or obstructive sleep apnoea, with no clear cause being identified in 4 individuals. Abnormal results were associated with increased weight (median 108.2 kg v. 87.9 kg, p<0.001), higher 24-hour urine volume (median 2705 ml v. 2039 ml, p<0.01) and the presence of obstructive sleep apnoea (OSA, 23.8% v. 6.9%, p<0.01)

Conclusion: No patients in this at-risk cohort were diagnosed with a PPGL. There was a significant false positive rate which was largely attributable to medications and/or OSA. Increased weight and larger 24-hour urine volumes were potentially implicated. These data question the utility and cost effectiveness of blanket PPGL screening from hypertension clinic. Weight-adjusted reference intervals may be useful to reduce the number of false positive results.