Morishita M, Maruyama Y, Nakao M, et al. - This retrospective cross-sectional study was undertaken to identify the factors impacting ionized calcium (iCa)/corrected calcium (cCa) ratio in peritoneal dialysis (PD) patients, by using multiple regression analysis. This analysis involved 169 PD patients, who were categorized into the first, second, and third tertile of iCa/cCa ratio groups. Longer PD duration and higher pH were observed in PD patients with lower iCa/cCa ratio. iCa/cCa ratio and weekly renal Kt/V were shown to be directly correlated, and independent factors influencing iCa/cCa ratio were weekly renal Kt/V and pH. Overall, PD patients with lower residual renal function (RRF) exhibited lower iCa levels despite having cCa levels equivalent to those with maintained RRF, this indicates that caution is warranted in the evaluation as well as treatment of chronic kidney disease-mineral and bone disorder in PD patients.