Dear Editor,
Segawa H et al. claim that the urinary sodium/potassium ratio can be used to screen for hyperaldosteronism; this finding appeared in your journal (Hypertension Research volume 44, pages1129–1137 (2021)). According to Table 3, the sensitivity for hyperaldosteronism by Na/K < 1.0 was ~45%, and the specificity was ~98%. When the cutoff point was increased to 3.0, the sensitivity was ~91%, and the specificity was ~40%. Therefore, the positive and negative likelihood for Na/K < 1.0 and <3.0 are 22.5 and 0.56 for <1.0 and 6.9 and 0.225 for <3.0. The prevalence of hyperaldosteronism is ~20% of hypertension, which suggests that most of the patients have normo- or low aldosteronism and that the Na/K ratio is above the cutoff point. When we screened hyperaldosteronism by Na/K < 1.0, 80% of the cases were Na/K > 1.0 (negative result), and the possibility of hyperaldosteronism was decreased by 0.56-fold. In contrast, when we set the cutoff point to Na/K < 3.0, the possibility of hyperaldosteronism decreased by 0.225-fold. In general, when screening for this disease, we should choose a lower negative likelihood test to avoid missing the disease. The Na/K ratio is ~4.6 from the INTERSALT study in East Asians [1] or lower (2.0) from NIPPON DATA80 [2]. These observations suggest that an appropriate Na/K cutoff for screening hyperaldosteronism is 3.0 which is not ‘low’ but instead is average for the Japanese population.
References
Iwahori T, Miura K, Ueshima H, et al. INTERSALT Research Group. Urinary sodium-to-potassium ratio and intake of sodium and potassium among men and women from multiethnic general populations: the INTERSALT Study. Hypertens Res. 2019;42:1590–1598. https://doi.org/10.1038/s41440-019-0263-1.
Okayama A, Okuda N, Miura K, et al. NIPPON DATA80 Research Group. Dietary sodium-to-potassium ratio as a risk factor for stroke, cardiovascular disease and all-cause mortality in Japan: the NIPPON DATA80 cohort study. BMJ Open. 2016;6:e011632. https://doi.org/10.1136/bmjopen-2016-011632.
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Shimosawa, T. Is the cut off point proper in screening of primary aldosteronism by urinary Na/K ratio. Japanese are still high in Na/K ratio. Hypertens Res 45, 551 (2022). https://doi.org/10.1038/s41440-021-00787-y
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DOI: https://doi.org/10.1038/s41440-021-00787-y