Identifying patients with chronic kidney disease who are at increased risk of death
A recent study has established a correlation between the level of fibroblast growth factor-23 (FGF-23) in the blood of a person with chronic kidney disease (CKD), measured over time, and the risk of death. This research could alert physicians to the need for improved care for these individuals. Previous studies have found that the hormone FGF-23 may play a key role in kidney function and in the initiation and progression of CKD. Premature death from all causes, and from cardiovascular disease in particular, is higher in people with CKD than in healthy adults. Increased FGF-23 levels in the blood have been shown to be associated with increased mortality in CKD. However, it has been unclear how these levels change over time in a person with CKD, and whether repeated testing of FGF-23 levels over long periods of time can better predict clinical outcomes.
In 2001, the NIDDK established the Chronic Renal Insufficiency Cohort (CRIC) study to identify the risk factors for loss of kidney function and the link between kidney and heart diseases, and to apply this acquired knowledge to improving health. In the current study, CRIC investigators examined circulating FGF-23 levels to see whether they increase over time and whether a rise in FGF-23 levels (i.e., a rising trajectory) is associated with an elevated risk of death among men and women with CKD. FGF-23 levels were measured in 1,135 CRIC participants at enrollment and then again 1, 2, 3, and 4 years later. Compared to levels when the participants first enrolled, FGF-23 levels rose slightly in later years for the group as a whole. However, using a special statistical analysis technique, the investigators identified three FGF-23 trajectory subgroups: stable, slowly rising, and rapidly rising. Unlike the subgroup whose FGF-23 levels remained stable over time, the 37 percent of participants in the slowly rising FGF-23 subgroup were at 4.5-fold higher risk of death, and the 7 percent of participants in the rapidly rising FGF-23 subgroup were at 15.2-fold higher risk of death. Thus, although stable in the majority of CRIC participants, rising FGF-23 levels in some people with CKD place them at exceptionally high risk of death. This finding could help kidney specialists identify patients with CKD at particularly high risk, based on rising FGF-23 levels, and thus provide more personalized care.