For example: i) patients in whom filtration markers (either creatinine, cystatin C or both) were thought to be insufficiently accurate, or those who were more likely to have large discrepancies between eGFRcr and eGFRcys; ii) patients who were under the care of clinicians who were more conscious of the importance of kidney function in cancer management; iii) patients under the care of clinicians managing specific cancer types or treatments where measuring GFR is more strongly advocated. The gene discussed is CST3; the disease is cancer.