Association of inflammation with anaemia in patients with chronic kidney disease not requiring chronic dialysis.

Background: Anaemia associated with chronic kidney disease (CKD) has substantial public health importance. However, the association of haemoglobin concentrations with inflammation in the setting of decreased kidney function is not well established.
Methods: We analysed cross-sectional data from 7389 outpatient adults, who were referred by general practitioners for routine blood testing between June 2006 and June 2007. Glomerular filtration rate (eGFR) was estimated by the abbreviated Modification of Diet in Renal Disease (MDRD) equation. Multivariable linear regression analysis was used to identify factors independently associated with haemoglobin concentrations across eGFR categories as the main outcome.
Results: Of the 7389 participants included in the analytic cohort 2221 (30.1%) participants had eGFR >/=90 mL/min/m(2), 4310 (58.3%) 60-89 mL/min/m(2) and 858 (11.6%) <60 mL/min/m(2). There were significant, graded, increases in high sensitivity C-reactive protein (hs-CRP) and haemoglobin concentrations across eGFR categories independent of age, gender, plasma glucose and lipids (P < 0.0001 for trends). In the multivariable regression analysis, increased hs-CRP concentrations were independently associated with lower haemoglobin concentrations at different stages of eGFR (P < 0.0001 for all). Other independent predictors of lower haemoglobin were older age, female gender and lower eGFR.
Conclusions: Our findings suggest that increased plasma hs-CRP concentrations are independently associated with anaemia in the setting of decreased kidney function in a large cohort of unselected adult outpatients.