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Relevance of C-reactive protein levels in peritoneal dialysis patients
1Section of Nephrology, University of Manitoba, Winnipeg, Manitoba, Canada. afine@sbgh.mb.ca
Insights
In peritoneal dialysis patients, infections and inflammation strongly predict high C-reactive protein (CRP) levels, not cardiovascular disease. Many elevated CRP levels lack clear causes and fluctuate over time.
Area of Science:
- Nephrology
- Clinical Chemistry
- Inflammation Research
Background:
- Elevated C-reactive protein (CRP) in 30-50% of dialysis patients is linked to cardiovascular risks.
- Raised CRP is typically attributed to atherosclerosis, but many patients with cardiovascular disease have normal CRP.
- This study investigates risk factors for high CRP and its utility in identifying cardiovascular disease and infections in peritoneal dialysis (PD) patients.
Purpose of the Study:
- To identify risk factors associated with elevated C-reactive protein (CRP) levels in peritoneal dialysis (PD) patients.
- To evaluate the effectiveness of CRP as a marker for clinically apparent coronary artery disease (CAD), peripheral vascular disease (PVD), and infections/inflammatory disorders (INF-INFL) in PD patients.
Main Methods:
- Retrospective chart review of 190 prevalent peritoneal dialysis patients.
- Collected data included CRP, albumin, ferritin, erythropoietin (EPO) dose and resistance, Kt/V, residual renal function, and presence of cardiovascular disease (CAD, PVD) and INF-INFL.
- Statistical analysis involved Chi-square, Spearman correlation, and logistic regression.
Main Results:
- 31% of patients exhibited elevated CRP levels.
- Infections/inflammatory disorders (INF-INFL) were highly predictive of raised CRP (OR 16.97), while CAD and PVD were not associated.
- High CRP levels were more common in females and patients with high transport status (OR 7.28), but not in diabetics. Many elevated CRP levels lacked identifiable causes and showed temporal variability.
Conclusions:
- Elevated CRP levels in peritoneal dialysis patients frequently occur without an apparent cause.
- Clinically apparent cardiovascular disease does not reliably predict high CRP levels.
- Further research is needed to identify non-obvious sources of inflammation in PD patients.
Background:
C-reactive protein (CRP) levels are increased in 30 to 50% of dialysis patients and predict cardiovascular morbidity and mortality. It is usually considered that raised CRP levels reflect underlying atherosclerosis. However, many patients may have clinically apparent cardiovascular disease without raised CRP levels. This study was designed to assess both the risk factors for high CRP levels and the usefulness of the test as a marker of clinically apparent coronary artery disease (CAD), peripheral vascular disease (PVD) and the presence of ongoing infections/inflammatory disorders (INF-INFL) in peritoneal dialysis patients.
Methods:
A chart review of 190 prevalent peritoneal dialysis patients was performed. CRP, albumin, ferritin, erythropoietin (EPO) dose and resistance, Kt/V, and residual renal function values were obtained and a history or presence of cardiovascular disease (CAD, PVD) and presence of INF-INFL recorded. Data were analyzed by Chi-square, Spearman correlation and logistic regression.
Results:
A total of 31% of patients had a raised CRP. INF-INFL was highly predictive of raised CRP levels (OR 16.97; 95% CI 5.41 to 53.14, P=0.000), whereas CAD and PVD either singly or in combination had no such association. The sensitivity/specificity for CRP as a test for INF-INFL was 83/77%. For CAD and PVD, the sensitivities were less than 40% and specificities 70%. Increased CRP values were more common in females but not in diabetics. Weak linear correlations existed between CRP levels and albumin, ferritin and residual renal function (r=-0.212, 0.228 and -0.163 respectively, P < 0.02). By regression analysis, INF-INFL predicted high CRP levels, but CAD and PVD did not. The majority of patients (57%) with high CRP had no identifiable cause; 40% of these patients had subsequent or previous normal CRP values. High transport status predicted high CRP levels (OR 7.28; 95% CI 1.417 to 37.36, P=0.006).
Conclusions:
The majority of elevated CRP levels in peritoneal dialysis patients occur without an obvious cause. Clinically apparent cardiovascular disease does not predict high CRP levels. CRP levels vary over time in the same patient, from normal to high or vice versa, for no obvious reason. Sources of inflammation other than CAD, PVD and clinically obvious INF-INFL in peritoneal dialysis patients remain to be identified.