Comment on “Urinary sodium-to-potassium ratio associates with hypertension and current disease activity in patients with rheumatoid arthritis: a cross-sectional study”: authors’ reply

[...]the most reliable method to diagnose sodium reactivity is the “salt intervention test,” which requires several days of intervention, and the intervention method and diagnostic criteria are not standardized [3]. [...]it is difficult to perform a sub-analysis in our study population. While the second paper suggested the higher expression of renin in RA than OA synovium, another report found no difference in the serum renin and angiotensin-converting enzyme (ACE) levels among RA, OA, and healthy control [7]. [...]the relationship between the RAA system and RA disease activity is not determined yet. Not only renin, but also various humoral hormones such as natriuretic peptides and adrenomedullin [8], could be involved in both inflammation and body fluid volume; thus, the effect of these humoral hormones on hypertension and RA disease activity may be worth studying in the future.