High-sensitivity C-reactive protein and the risk of chronic kidney disease progression or acute kidney injury in post-myocardial infarction patients

Background Persistent, low-grade inflammation likely participates in the pathophysiology of both atherosclerosis and kidney disease. Although high-sensitivity C-reactive protein (hsCRP) predicts future cardiovascular risk in patients with chronic kidney disease (CKD), it is unknown whether hsCRP levels predict adverse renal outcomes in patients with cardiovascular disease. Methods We studied all myocardial infarction (MI) survivors undergoing hsCRP testing >30 days after their MI during routine health care in Stockholm, Sweden (2006-2011), with available information on estimated glomerular filtration rate (eGFR). HsCRP tests measured during hospitalization/emergency room visits, followed by antibiotics or indicative of acute illness, were excluded, together with patients with ongoing/recent cancer, chronic infections, or immunosuppression. Inflammation was defined over a 3-month baseline window. Study outcomes were CKD progression (composite of doubling plasma creatinine, renal replacement therapy, or renal death) and acute kidney injury (AKI, acute creatinine peaks according to Kidney Disease: Improving Global Outcomes criteria). Multivariable Cox regression was used to adjust for age, sex, eGFR, hemoglobin, time since MI, comorbidities, undertaken procedures, and medications. Results A total of 12,905 patients (62% men, mean age 73 years and 3 years since MI) were included, of whom 35% had an eGFR<60 mL/min/1.73 m(2). The mean (SD) hsCRP was 3.0 (4.4) mg/L. Baseline hsCRP levels were increasingly higher across lower eGFR categories. During a median follow-up of 3.2 years, 1,019 CKD progressions and 1,481 AKI events were recorded. Patients with hsCRP >= 2 mg/L were at higher risk of both CKD progression (adjusted hazard ratio 1.42; 95% CI 1.21-1.66) and AKI (1.29; 1.13-1.47) compared to those with hsCRP <2 mg/L. This association persisted across single CKD severity stages and after further hsCRP categorization into 4 groups (<= 1, 1-3, 3-10, >10 mg/L). Results were robust across subgroups of patients and after exclusion of events occurring during the first 6-12 months. Conclusions In post-MI patients undergoing routine health care, elevated hsCRP was associated with subsequent risk of AKI and progression of CKD, irrespective of baseline kidney function.