A United Kingdom-wide audit of the laboratory investigation of primary aldosteronism

Abstract

Objectives

Primary aldosteronism (PA) is a common but under-recognised cause of secondary hypertension. Early diagnosis with targeted medical and/or surgical intervention is important to prevent irreversible end-organ damage. An Endocrine Society Clinical Practice Guideline was used to define audit standards against which to assess current United Kingdom (UK) laboratory practice.

Methods

A survey comprising 22 questions, which captured information on screening, confirmatory testing and adrenal vein sampling (AVS), was distributed to all UK Clinical Biochemistry laboratories by the Association for Laboratory Medicine. Consultation with clinical colleagues was encouraged.

Results

50 of 147 laboratories (34.0%) responded, 17 of which provided an analytical service for plasma aldosterone concentration (PAC) and renin, measured as plasma renin activity (PRA) or direct renin concentration (DRC). PRA/DRC, PAC and aldosterone:renin ratios were used to screen for PA. Saline infusion testing was the most common confirmatory test. AVS was used to aid lateralisation. Chemiluminescence immunoassay and liquid chromatography tandem mass spectrometry were the preferred analytical methods for PAC and PRA/DRC. However, there was considerable variation across centres in respect of reference intervals and cutoffs, which were not fully accounted for by differences in analytical platforms. Although diagnostic algorithms, with pre- and post-analytical support, were in evidence in some centres, these were not universal or always embedded in a multidisciplinary team setting.

Conclusions

We observed significant heterogeneity in the laboratory investigation of PA across the United Kingdom. Therefore, this work serves as a stimulus for greater collaboration to permit national harmonisation/standardisation of analytical and clinical aspects of UK PA practice.