KL and chronic kidney disease: Similarly, Kim et al completed an observational study with 243 CKD patients divided into two groups based on circulating levels of a-Klotho and showed that 35.2% of the group that had lower levels reached the primary composite outcome (doubling of baseline serum creatinine concentration, end-stage renal disease, or death) compared to 15.7% of the group with high a-klotho levels (HR, 2.03; 95% CI, 1.07–3.85; p = 0.03).