Gender-specific spKt/V thresholds associated with mortality in maintenance hemodialysis patients: a nationwide Korean cohort study

Clinical guidelines recommend a single-pool Kt/V (spKt/V) target of 1.2–1.4 per hemodialysis (HD) session, but optimal adequacy targets may differ by sex. We examined sex-specific associations between spKt/V and all-cause mortality in a nationwide Korean cohort of maintenance HD patients. Using data from the 2015 HD Quality Assessment and National Health Insurance Service, we included 29,349 adults on thrice-weekly HD. The association between spKt/V and mortality was estimated using Cox models, and Harrell’s C-index was used to derive sex-specific prognostic cut-off values. Of the cohort, 17,171 (58.5%) were men and 12,178 (41.5%) women, with mean follow-up 53.8 ± 23.0 months. The mean spKt/V was higher in women (1.71 ± 0.27) than in men (1.44 ± 0.22). In men, mortality was higher at spKt/V < 1.2 (HR 1.25, 95% CI 1.14–1.37), with no additional benefit at 1.4 or higher. In women, survival improved in the higher categories (1.4–1.7: HR 0.86; ≥ 1.7: HR 0.73). C-index analysis identified a prognostic cutoff of 1.21 for men and 1.51 for women. These findings suggest that uniform adequacy thresholds may not fully reflect sex-related prognostic differences. The identified spKt/V values should be interpreted as data-driven prognostic reference points rather than prescriptive treatment targets, and warrant validation in prospective studies.