Haemoglobin variability in Chinese pre-dialysis CKD patients not receiving erythropoietin

Although originally described in dialysis patients treated with recombinant human erythropoietin (rHuEPO), haemoglobin variability has recently also been noted to be increased in patients who have chronic kidney disease (CKD) without dialysis. In our country, pre-dialysis CKD patients generally would not receive rHuEPO treatment. We studied the degree of haemoglobin variability and its prognostic implication in this group of patients.

We reviewed 332 patients with Stages 3 through 5 CKD; patients with overt iron deficiency or requiring blood transfusion were excluded. Patients were followed for up to 5 years. End points include all-cause mortality, progression to dialysis-dependent renal failure and hospitalization.

The average haemoglobin level was 11.4 ± 2.8 g/dL; intra-individual SD of haemoglobin was 0.76 ± 0.61 g/dL. Haemoglobin variability, as represented by intra-individual SD of haemoglobin, was significantly associated with the average haemoglobin level (r = -0.130, P = 0.017), Charlson's comorbidity score (r = 0.113, P = 0.040) and proteinuria (r = 0.151, P = 0.044). Univariate analysis showed that patients with high haemoglobin variability had a significantly higher all-cause mortality (log-rank test, P = 0.030) and risk of progression to end-stage renal disease (log-rank test, P = 0.021) and was associated with the adjusted duration of hospitalization (r = 0.134, P = 0.015). However, all associations become statistically insignificant after multivariate analysis to control for confounding factors.

Fluctuation of haemoglobin level is common and substantial in Chinese pre-dialysis CKD patients. Our results suggests that the observed clinical effect of haemoglobin variability in this patient population is an epiphenomenon secondary to the association between haemoglobin variability and other clinical factors.