Is It Possible to Screen for Primary Aldosteronism Effectively in Primary Care?

Abstract

Objective: Primary aldosteronism (PA) is the commonest secondary cause of hypertension but case-detection remains a challenge. Screening is usually performed in secondary care using an aldosterone:renin ratio (ARR) measurement. Here, we describe the outcomes of screening in primary care, in Oxfordshire, UK.

Design: Retrospective observational study.

Patients: Adults screened for PA in primary care services in Oxford between 2008 and 2022.

Measurements: ARR test results in primary care and outcomes of secondary care evaluation (ARR, saline infusion test, final diagnosis). Primary care and secondary care ARR tests were compared for correlation, concordance and performance in predicting PA.

Results: Among 2915 adults screened in primary care, 455 were referred to secondary care and 107 (3.7% of total population screened) were diagnosed with PA. Primary care ARR showed strong correlation with secondary care ARR (r = 0.841, p < 0.001). Area under the ROC curve to predict PA was 0.81 (95% CI 0.77-0.86) for primary care ARR testing. Primary care ARR cut-off of ≥ 30 pmol/mU showed comparable sensitivity (91.7% vs 92.1%, p = 0.467) to and modest concordance (Kappa 0.583, p < 0.001) with secondary care ARR. Use of beta-blockers were associated with higher risk of false positive test result (OR 3.5, 95% CI 1.1-12.0, p = 0.042).

Conclusions: Screening for PA in primary care with ARR is feasible with modest concordance and comparable sensitivity to secondary care testing. Simple referral criteria and raising awareness among primary care colleagues could ensure appropriate referral to secondary care.

Keywords: case detection; endocrine hypertension; general practice; hyperaldosteronism; resistant hypertension.

Figure 1

Outcomes of people screened for primary aldosteronism in primary care. All percentages are out of total population screened (N = 2915). Positive test was defined as ARR ≥ 1000 h⁻¹ before 2015 and ≥ 30 pmol/mU after 2015. Data on final diagnosis was not available from 16 individuals due to on‐going investigations (n = 6) or lost to follow up/unavailability of data in electronic records (n = 10). ARR, aldosterone renin ratio; PA, primary aldosteronism; PC, primary care; SC, secondary care.

Figure 2

Primary care screening patterns over time. (a) Number of individuals screened for primary aldosteronism PA in primary care (PC) with aldosterone ratio (ARR) test (N = 2915). (b) Percentage of primary care screened individuals referred to secondary care (in total, 263 of 365 with a positive primary care ARR and 192 of 2550 with a negative primary care ARR were referred). Positive test was defined as ARR ≥ 1000 h⁻¹ before 2015 and ≥ 30 pmol/mU after 2015.

Figure 3

Percentage of patients diagnosed with confirmed or possible PA (a) across different indications [among 439 patients whose outcome of diagnostic evaluation was known], and, (b) by the number of antihypertensive medications used [among 253 individuals whose outcome of diagnostic evaluation and medication data were known]. Number of antihypertensive medications were determined by reviewing the prescription at the time of primary care testing. Among 50 individuals who were not on antihypertensives at the time of primary care ARR test, 13 were commenced on antihypertensive medication after the ARR test. PA, primary aldosteronism.