Outcomes predicted by phosphorous in chronic kidney disease: a retrospective CKD-inception cohort study.
BACKGROUND
The impact of secondary hyperparathyroidism on morbidity and mortality among patients with chronic kidney disease (CKD) is unclear.


METHODS
We conducted a retrospective cohort study to investigate the relationship between CKD and serum phosphorous. Through clinical databases at a large health maintenance organization, we identified a dynamic CKD inception cohort between 1997 and 2004, with stage 3-5 kidney disease with subsequent phosphorous measurement; the patients were followed up for up to 5 years for outcomes of mortality, cardiovascular mortality, cardiovascular hospitalizations and renal replacement therapy (RRT; dialysis or transplant). Survival analysis with time-varying covariables for phosphorous and renal function estimated the relationship between phosphorous level and outcomes, adjusting for potential confounding variables.


RESULTS
A total of 930 patients with complete data were included in our analysis; they had a higher disease burden than excluded patients. Phosphorous did not predict overall or cardiovascular mortality, or cardiovascular hospitalizations. The rate of RRT increased significantly with the level of phosphorous, even when controlling for renal function.


CONCLUSIONS
Contrary to some previous reports, we did not find evidence of increased mortality with phosphorous, but did find that increased levels of phosphorous are related to excess rates of RRT. Our work does not suggest that controlling phosphorous will lower the risk of RRT; our work motivates randomized controlled trials to investigate the clinical value of such interventions.
Smith
David H
DH
Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon, USA. David.H.Smith@kpchr.org
Johnson
Eric S
ES
Thorp
Micah L
ML
Petrik
Amanda
A
Yang
Xiuhai
X
Blough
David K
DK
D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002908:Chronic Disease; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000150:complications; D007674:Kidney Diseases / Q000097:blood* / Q000175:diagnosis* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010758:Phosphorus / Q000097:blood*; D011237:Predictive Value of Tests; D011379:Prognosis; D017582:Renal Replacement Therapy; D012189:Retrospective Studies; D016019:Survival Analysis
D015415:Biomarkers; D010758:Phosphorus