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Serum phosphorus and calcium levels, and kidney disease progression in immunoglobulin A nephropathy
Guizhen Yu1,2,3,4,5, Jun Cheng1,2,3,4,5, Yan Jiang1,2,3,4,5
1Kidney Disease Center, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
Insights
Higher serum phosphorus levels are linked to kidney disease progression in IgA nephropathy patients. Serum calcium levels did not show a significant association with disease progression.
Area of Science:
- Nephrology
- Mineral Metabolism
- Chronic Kidney Disease
Background:
- Disorders in calcium and phosphorus metabolism are linked to mortality in dialysis patients.
- The role of these minerals in disease progression for non-dialysis patients, particularly IgA nephropathy, is not well-established.
Purpose of the Study:
- To investigate the association between serum phosphorus and calcium levels and the progression of IgA nephropathy.
Main Methods:
- Assessed 2567 IgA nephropathy patients, collecting serum phosphorus and calcium data.
- Utilized Cox models and restricted cubic splines to examine associations with composite kidney disease progression events (50% eGFR decline or kidney failure).
Main Results:
- Higher serum phosphorus levels showed a linear relationship with increased risk of kidney disease progression (HR 3.54).
- The association was significant in patients with eGFR <60 mL/min/1.73 m² but not in those with eGFR ≥60 mL/min/1.73 m².
- Serum calcium levels were not significantly associated with kidney disease progression after adjustment for risk factors.
Conclusions:
- Elevated serum phosphorus is an independent risk factor for kidney disease progression in IgA nephropathy.
- Serum calcium levels do not appear to influence IgA nephropathy progression.
Background:
Disorders of calcium and phosphorus metabolism have been reported to be associated with all-cause and cardiovascular mortality in patients requiring long-term dialysis therapy. However, its role in disease progression is not well established in patients without dialysis, especially in immunoglobulin A (IgA) nephropathy. We aim to evaluate the association of serum phosphorus and calcium and progression of IgA nephropathy.
Methods:
We assessed 2567 patients with IgA nephropathy at the First Affiliated Hospital, College of Medicine, Zhejiang University. Serum phosphorus and calcium were collected at the time of kidney biopsy and at each visit. The associations of serum phosphorus and serum calcium with composite kidney disease progression events, defined as 50% estimated glomerular filtration rate (eGFR) decline and kidney failure, were examined using Cox models and restricted cubic splines.
Results:
During a median follow-up of 31.9 months, 248 (10%) patients reached composite kidney disease progression events. A linear relationship was observed between serum phosphorus and composite kidney disease progression events. With higher levels of phosphorus, the risk of kidney disease progression events increased {hazard ratio [HR] 3.54 [95% confidence interval (CI) 1.37-9.12]; P = 0.009}. Compared with the first quartile group, the HR of kidney disease progression events was 1.66 (95% CI 0.91-301) for the second quartile, 1.67 (95% CI 0.91-3.08) for the third and 2.62 (95% CI 1.44-4.77) for the fourth (P for trend = 0.002). The association between serum phosphorus and kidney disease progression was detectable [HR 8.94 (95% CI 2.33-34.21); P = 0.001] within the subgroup with eGFR <60 mL/min/1.73 m2 but not among patients with eGFR ≥60 mL/min/1.73 m2 [HR 0.87 (95% CI 0.17-4.44); P = 0.87]. After adjustment for traditional risk factors, a higher level of serum calcium was not associated with kidney disease progression events [HR 0.33 (95% CI 0.10-1.09)].
Conclusions:
Higher serum phosphorus rather than serum calcium was independently associated with kidney disease progression in IgA nephropathy.
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