What is the clinical significance of the urine potassium (K+) to creatinine ratio?

From the Research

Clinical Significance of Urine Potassium (K+) to Creatinine Ratio

The urine potassium (K+) to creatinine ratio is a useful marker for diagnosing renal potassium loss and assessing 24-hour urinary potassium excretion.

• The ratio has been shown to have a moderate correlation with 24-hour urinary potassium excretion 1, 2, 3.
• A study found that a random urine potassium-to-creatinine ratio (rUK/Ucr) of 3.4 or higher can be used to diagnose renal potassium loss with a sensitivity of 67.6% and a specificity of 67.5% 1.
• Another study found that the fractional excretion of potassium (FEK) from a spot urine sample can predict renal potassium loss in hypokalemia with high accuracy, and that FEK showed the highest correlation with 24-hour urinary potassium excretion 4.
• The urine potassium-to-creatinine ratio has also been found to be associated with the progression of chronic kidney disease (CKD), with lower ratios indicating a higher risk of CKD progression 5.

Diagnostic Value

The diagnostic value of the urine potassium-to-creatinine ratio has been evaluated in several studies.

• One study found that the area under the curve (AUC) for the ratio in predicting renal potassium loss was 0.71, comparable to the AUC for 24-hour urinary potassium excretion 1.
• Another study found that the AUC for the ratio in predicting 24-hour urinary potassium excretion was 0.802 for values above 120 mmol/24h, but poorer for lower values 2.
• The ratio has also been found to be a useful marker for estimating 24-hour urinary potassium excretion, especially when 24-hour urine collection is not available 2, 3.

Association with Kidney Disease

The urine potassium-to-creatinine ratio has been found to be associated with kidney disease.

• A study found that lower urinary potassium excretion, as indicated by a lower potassium-to-creatinine ratio, was associated with a higher risk of CKD progression 5.
• Another study found that the ratio was significantly correlated with 24-hour urinary potassium excretion, which is an important marker for kidney function 3.