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Retrospective analysis of abnormal 24-h urinary free catecholamine concentration in screening for phaeochromocytoma
Iskandar R Idris1, Robert Hill, Keith A Sands
1Kings Mill Centre for Health Care Services and John Pease Diabetes Centre, Sutton-in-Ashfield, UK. is.idris@nottingham.ac.uk
Insights
Hypertension is linked to higher noradrenaline (NA) levels in 24-hour urine. Beta-blockers may further increase NA, complicating phaeochromocytoma diagnosis in hypertensive patients.
Area of Science:
- Endocrinology
- Nephrology
- Clinical Chemistry
Background:
- Hypertension is often associated with elevated 24-hour urinary free catecholamines (UFCA).
- The impact of antihypertensive medications, particularly beta-blockers, on UFCA levels is not fully understood.
- This uncertainty can lead to underinvestigation for phaeochromocytoma in patients with borderline UFCA results.
Purpose of the Study:
- To investigate the relationship between hypertension, beta-blockade, and 24-hour UFCA concentrations.
- To assess the diagnostic yield of investigating elevated UFCA in hypertensive patients.
- To evaluate the prevalence of phaeochromocytoma in patients with abnormal UFCA.
Main Methods:
- Retrospective audit of 168 patients with abnormal 24-hour urinary adrenaline (Adr), noradrenaline (NA), or dopamine (DA) collections.
- Analysis of hospital records for 106 patients with available notes.
- Comparison of NA excretion between hypertensive and normotensive patients, and assessment of beta-blocker effects.
Main Results:
- Two out of ten patients who underwent imaging for elevated UFCA (more than twice the upper limit) were diagnosed with phaeochromocytoma.
- Hypertensive patients showed significantly higher NA excretion (median 490 nmol/24h) compared to normotensive individuals (median 304 nmol/24h).
- A trend towards increased NA excretion was observed in patients taking beta-blockers (P=0.08).
Conclusions:
- Many patients with abnormal UFCA are not adequately investigated for phaeochromocytoma.
- Elevated NA concentrations are significantly associated with hypertension.
- Caution is advised when interpreting elevated NA levels in hypertensive patients or those on beta-blockers due to potential confounding factors.
Background:
Patients with hypertension often have increased 24-h excretion of urinary free catecholamines (UFCA) compared with normotensive patients, but the extent to which beta-blockade and other antihypertensive agents affect 24-h UFCA concentrations remains unclear. Consequently, many patients with slightly elevated 24-h UFCA concentrations are not adequately investigated for the presence of phaeochromocytoma.
Method:
We undertook a retrospective study on patients with at least one abnormal 24-h urinary collection of adrenaline (Adr), noradrenaline (NA) or dopamine (DA) between July 1997 and December 1999 to assess these issues.
Results:
Of the 168 patients identified with raised 24-h UFCA concentrations, 106 with hospital notes were audited. Of the 46 patients whose values were more than twice the upper reference limit, 24 had their result confirmed with a repeat sample and only 10 underwent computed tomography or m-iodobenzylguanidine scanning. Two patients of these 10 had a phaeochromocytoma. We observed that hypertension correlated with significantly increased NA excretion compared with normotensive patients (median value 490+/-222 nmol per 24 h versus 304+/-229 nmol per 24 h, P<0.005). Patients on beta-blockers showed a trend towards significantly increased NA excretion (P=0.08).
Conclusions:
Many patients with abnormal 24-h UFCA excretion are not thoroughly investigated for the presence of phaeochromocytoma. NA concentration is significantly raised above the reference limit for patients with hypertension, and the use of beta-blockers showed a trend towards a further elevation in NA concentrations. Care must therefore be taken when interpreting abnormal NA concentrations in patients with hypertension or in those taking beta-blockers.