Endocrine Abstracts (2001) 2 P93

AMBULANT ALDOSTERONE/ ACTIVE RENIN RATIOS AS A SCREEN FOR CONN'S SYNDROME; INFLUENCE OF DRUG THERAPY

A Armston1, DG Waller2, AJ Krentz2, DD Sandeman2, BA Leatherdale2 & PJ Wood1


1Regional Endocrine Unit, Southampton General Hospital, Southampton, UK; 2Dept of Medicine, Southampton General Hospital, Southampton, UK.


Primary hyperaldosteronism ('Conn's syndrome') may have a prevalence as high as 10% in hypertensive patients, and in some cases there may not be obvious hypokalaemia. Recently the use of a single aldosterone/ renin ('A/R') ratio has been advocated as a screening test for Conn's, and less influence by anti-hypertensive drug therapy has been claimed.We have established a cut-off for ambulant A/R ratios of 25 ng/mU using the DPC'Coat-a-Count' aldosterone method and the Nichols 'Active' renin assay (with an additional lower standard to give a lower detection limit).The influence of anti-hypertensive drug therapy has been studied in 29 patients under investigation for suspected Conn's syndrome. Overall, the ambulant A/R ratios were slightly but significantly lower in patients on drug teatment (p less than 0.05; Wilcoxon test) with 22/29 patients showing lower values. Using the cut-off of 25 ng/mU for A/R ratios there were no false negative results when a single ambulant A/R ratio was determined while patients were on drug treatment. One false positive result was obtained on drug therapy (3.4%). We conclude that the ambulant A/R ratio is acceptable as a screen for Conn's syndrome.

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