The clinically significant estimated glomerular filtration rate for hyperkalemia

Reduced glomerular filtration rate (GFR) is a risk factor of cardiovascular diseases. Accurate assessment of GFR together with early and appropriate treatment of chronic kidney disease (CKD) is important. Although the Japanese Society of Nephrology has recently announced two equations (equation 0.741 and equation 194) to estimate GFR for Japanese, the clinically significant estimated GFR (eGFR) in Japanese has not been identified. We examined the clinical significance of eGFR with regard hyperkalemia.

A total of 9,196 patients who were examined and treated at the Toranomon Hospital between January and October 2005 were studied. Patients with a serum potassium level of 5 mEq/L or above or who were taking potassium adsorbent were classified as hyperkalemic. The effect of eGFR on the incidence of hyperkalemia was examined. The factors causing elevated serum potassium were analyzed after excluding the patients on potassium absorbent.

Multivariate analysis identified reduced eGFR, diabetes, male gender, aging, and use of renin-angiotensin system inhibitors as the factors associated with an elevated serum potassium level. In an eGFR-stratified analysis, each subgroup with eGFR below 50 mL/min/1.73 m2when equation 0.741 was used, and eGFR below 60 mL/min/1.73 m2 when equation 194 was used had a significantly higher incidence of hyperkalemia compared with almost all of the subgroups with higher eGFR.

From the viewpoint of the increase in incidence of hyperkalemia, using an eGFR below 50 mL/min/1.73 m2 as the cutoff has clinical significance when equation 0.741 is used and a cutoff at 60 mL/min/1.73 m2 is appropriate when equation 194 is used.