Blood transfusions were prevalent among ND-CKD patients with severe anemia recently treated within the Henry Ford Health System. Prior hospitalization consistently predicted a higher transfusion rate among these patients and patients with more days in the hospital prior to the anemia index date had more transfusions. A hemoglobin concentration around 9 g/dL was the mean level closest to the transfusion, indicative that this level may be the trigger for a blood transfusion in this population although a substantial proportion occurred at Hb > 9.0 g/dL. These findings provide new evidence of the transfusion burden among anemic ND- CKD patients treated in routine clinical practice.
A few other studies have provided estimates of transfusion frequency for anemic non-dialysis CKD patients; however, these studies included unique patient populations and less current practice trends. Lawler and colleagues  observed a transfusion frequency of 8.5%-15.6% among patients with Hb < 11 g/dL receiving care in the Veterans Health Administration (VHA) between 2003 and 2005. The VHA study required patients to have only 1 Hb < 11 g/dL to be included in the study. In comparison, the proportion of patients who had a transfusion of 20% in the present study may be higher due to differences in the composition of the study population; in the VHA study, 80% of patients were white, 97% of patients were men, and the definition of anemia differed compared to our study.
The present study also evaluated transfusion burden among severe anemia defined as Hb < 10 g/dL and confirmation with subsequent treatment or second Hb < 10 g/dL) non-dialysis CKD patients. A study of Medicare beneficiaries  between 1992 and 2004 observed an adjusted transfusion rate of 112.2 per 1000 patient-years in 2004, which is lower than the present study adjusted rate of 182.2 per 100 patient-years. The higher transfusion frequency in the present study may be due to the following factors:1) inclusion of only stage 3-5 CKD with confirmed anemia whereas the Ibrahim study  included all CKD stages with approximately 60% of patients without anemia, 2) inclusion of patients enrolled in a commercial health plan (HFHS managed care) whereas Ibrahim excluded commercial health plan members and focused on Medicare patients, 3) significantly larger proportion of African Americans (50%) compared with 15% in the Ibrahim study, and 4) current trends in utilization of transfusion (up to December 2009) with longer follow-up time than the 1 year point prevalence of the Ibrahim study. The HFHS did not follow a defined transfusion protocol during the time of this study but the clinical directive was to maintain Hb at 10 g/dL or higher. With the goal of maintaining Hb ≥ 10 g/dL, patients' anemia symptoms (e.g. fatigue, lack of energy) and consequences of potential allosensitization were considered in the clinical decision to transfuse CKD patients.
Based on treatment patterns observed among CKD patients treated at the HFHS, a hemoglobin level around 9 g/dL appears to trigger the majority of blood transfusions. However, approximately 21% of transfusions occurred when the closest, preceding Hb level was ≥ 10 g/dL. This may be because more than one-third (38%) of the high Hb (≥ 10 g/dL) transfusions were second and subsequent transfusions and the treating physician may not have waited for the Hb results to order subsequent transfusions given the patient's medical history. Additionally, the reasons for transfusions might not be solely based on the Hb levels; patients' symptoms will also influence physician's decisions.
A key reason for patients with CKD to avoid blood transfusions is the risk of developing allo-antibodies which prolong the time on the kidney transplant waiting list and possibly jeopardize the kidney transplant outcome . In addition, blood transfusions are not without risks, including transfusion reactions, transmission of infectious agents, and iron overload . Providing adequate iron stores and using ESAs, may help to reduce the need for transfusions. A better understanding of the reasons for blood transfusions may help to elucidate other pathways to reducing the transfusion burden.
Minority races (African American and other races) had a higher unadjusted rate of transfusion than Whites but after controlling for other characteristics, the adjusted transfusion rate did not differ across racial groups. This may be due to the small number of patients who received transfusions in this study; 24 Whites, 47 African Americans and 4 other races were transfused in this study.
Several study limitations should be considered. The population served by HFHS is primarily from the greater metropolitan Detroit, MI area. As such this region may not be representative of the US population and have different treatment patterns for CKD-related anemia. Thus, the study findings may be limited to non-dialysis CKD patients with anemia and not generalizable to all CKD patients. The definition for severe anemia used in the study is limited in capturing chronic, severe anemia since it used one Hb < 10 g/dL followed by treatment or a second Hb < 10 g/dL. Of the 303 patients included in the cohort with a second Hb < 10 g/dL, 60% had the second Hb level 1-2 days after the first Hb so the anemia may not be chronic or persistent for some patients. Also, only 75 patients received transfusion during the study period, which limited the likelihood to observe statistically significant differences. For example, 13 patients had a prior transfusion and only 5 of these 13 patients had a transfusion during follow-up.