Urine to phosphate-to-creatinine ratio may predict adverse outcomes in people without CKD
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Due to a significant association between the urine to phosphate-to-creatinine ratio and mortality among individuals without chronic kidney disease, researchers suggest this may be a predictor for future adverse events in this population.
Further, no correlation was detected between urine to phosphate-to-creatinine (uPiCr) and all-cause and cardiovascular mortality in the entire cohort.
“Dietary phosphate intake is only weakly linked to serum phosphate levels and the relationship between phosphate intake and adverse outcomes remains unclear. Several studies have reported associations between phosphate intake and adverse outcomes in both CKD and general population cohorts,” Nigel D. Toussaint, MBBS, FRACP, PhD, from the department of nephrology at the Royal Melbourne Hospital in Australia, and colleagues wrote. “The small number of studies that have examined phosphate excretion, either 24-hour [urinary phosphate excretion] UPE or uPiCr, have reported conflicting associations with all-cause and CVD mortality.”
In an observational longitudinal cohort study, researchers examined 10,014 participants (median age was 50 years; 46% were men) from the Australian Diabetes, Obesity and Lifestyle study. Participants completed demographic surveys, and researchers collected blood and urine samples at on-site visits.
All-cause and CVD mortality served as the primary outcomes of the study. Using fractional polynomial transformations, researchers measured non-linear associations between uPiCr and all-cause and CVD mortality. Additionally, researchers used Cox proportional hazards regression models to determine adjusted hazard ratios for all cause and CVD mortality.
During a median follow-up of 16.9 years, 1,735 participants died. Overall, the mean uPiCr was 1.38 mmol/mmol. In univariate models, uPiCr correlated with all-cause and CVD mortality, but did not show significant associations in multivariate models.
Sensitivity analyses of participants without CKD revealed a significant J-shaped correlation between uPiCr and all-cause mortality. Similarly, urine phosphate alone showed a correlation with increased all-cause mortality.
“Spot urine measurement for uPiCr may be a surrogate marker for daily urinary phosphate excretion and our study demonstrates an association with all-cause mortality in a large general population cohort when participants with CKD were excluded. Confirmation of these findings may allow uPiCr to be utilized as a simple tool alongside other initial assessments of CVD risk and mortality,” Toussaint and colleagues wrote. “Given the increasing evidence of an association between phosphate and CVD, it is important to prospectively investigate whether interventions aimed at reducing phosphate burden, such as restricting dietary phosphate intake and limiting food additives, reduce cardiovascular events and mortality.”
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