Background: Circulating monocytes can be divided into distinct populations according to their expression of surface markers CD14 and CD16. In patients with chronic kidney disease (CKD), the cell fraction expressing high levels of CD14 and CD16 is expanded and the numbers of these cells are predictive for cardiovascular disease. The present pilot study describes the predictive role of a combined biomarker consisting of high numbers of CD14(++)CD16(+) cells together with high expression of angiotensin-converting enzyme (ACE) on these cells for mortality in CKD Stage V(D) (dialysis) patients.
Methods: In a prospective observational study, monocyte subpopulations were enumerated and ACE expression was quantified in 74 CKD patients by flow cytometry. Patients were assigned to one of four groups according to monocyte population numbers and ACE expression below and above the respective medians and observed for mortality and cardiovascular events for 46 months.
Results: Patients stratified to the 'high CD14(++)CD16(+), high ACE' group (n = 22) had a dramatically enhanced mortality of 70% at 2 years compared to all other patient groups (mortality 14.8%, HR 4.86 [95% CI 2.17-10.86, P < 0.0001]). Atherosclerosis-associated events predominated among the causes of death.
Conclusions: This study describes a new combined biomarker of monocyte subpopulation numbers together with high expression of ACE that has a striking predictive value for mortality of CKD patients. Further research into the pathophysiologic background of this observation is warranted.