GLA and chronic kidney disease: All CKD patients were screened by analyzing GLA activity in dried venous blood spots (DBS) and, when enzyme activity was lower than 1.2 micromole/L/h, the GLA gene was sequenced, except for 397 patients of C1 study in which an innovative method, the dosage of Gb3 and lyso-GB3 in dried urine spots, was used.