Endocrine Abstracts (2008) 16 P40

Comparison of strategies for biochemical diagnosis of primary aldosteronism in German academic centres

S Reuschl1, C Schirpenbach1, S Hahner3, F Beuschlein1, S Diederich4, R Lorenz5, LC Rump6, J Seufert7, S Endres1, M Quinckler2, M Reincke1 & M Bidlingmaier1

1Medizinische Klinik Innenstadt; Ludwig-Maximilians-Universität, Munich, Germany; 2Klinische Endokrinologie, Charité Campus Mitte, Charite Universitätsmedizin, Berlin, Germany; 3Medizinische Klinik und Poliklinik I, Julius-Maximilians-Universität, Würzburg, Germany; 4Endokrinologikum, Berlin, Germany; 5Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten, Ludwig-Maximilians-Universität, Munich, Germany; 6Marienhospital, Ruhr-Universität Bochum, Herne, Germany; 7Medizinische Klinik II, Albert-Ludwigs-Universität, Freiburg, Germany.

Recent studies indicating that normokaliemic primary aldosteronism (PA) is a more frequent cause of hypertension than previously expected led to an increased interest in biochemical screening strategies. We investigated biochemical diagnostic strategies used in different academic centres for patients documented in the German National Conn’s Registry. Data from 7 centres in 5 cities have been entered into a database by trained personnel. For analysis, results from 522 patients with documented results of measurements of aldosterone (A) in plasma or urine, renin concentration (RC) or renin acitivity (RA) were used, 85% of the results being obtained between 1997 and 2006. Aldosterone to renin ratio (ARR) was documented in 81.4% of patients, but used as first diagnostic step in only 64.7% (range 43.3–79.1% depending on centre). In 35.3% (range 20.9–56.7%) of patients, the first documented biochemical result was obtained already during a confirmatory or differential diagnostic test (salt load, posture test, lasix-renin test, adrenal vein sampling). Urinary aldosterone was analysed in only 4.6% of patients. ARR was documented in 66.7% (range 89.4–43.6%) during the first week of diagnosis. Documentation of variables potentially influencing ARR was poor (medication 70%, K 42.5%). Medication was adequately paused in 93.2% (mineralocorticoid receptor antagonists) and 59.4% (beta blocker). About 67% of patients were normokaliaemic at ARR determination. ARR values were calculated from 8 different combinations of assays (A plus RA or RC), with one or more changes in methods during the observational period in 6 of 7 centres. Mean A, RC and RA concentrations differed significantly between methods, as did the corresponding ARR. The highest ARR was observed for the combination Adalits A/Adaltis RA and DPC A/Nichols RC. In conclusion, diagnostic strategies differed between centres, which might also be reflected in a different composition of patient’s populations.