To the Editor
We read with great interest the article of Choi et al regarding the better treatment of preoperative anemia: red blood cell (RBC) transfusion or intravenous (IV) iron.
We welcome studies examining the best treatment of preoperative anemia, as many studies have shown an unfavorable association with outcome. To address this topic the authors have performed a database study in patients with iron-deficiency anemia receiving treatment with only IV iron or only RBC transfusion before surgery. These patients were matched in a one-on-one fashion based on many variables, resulting in a large-sized cohort of 154,358 patients. Compared to RBC transfusion, IV iron was associated with a 37% lower risk of mortality and a 24% lower risk of combined morbidity after surgery. However, there are several concerns we would like to address. Our first and main concern is that preoperative treatment with IV iron was compared to RBC transfusion, a well-known risk factor for worse postoperative outcomes that has been repeatedly established. For this reason, patient blood management (PBM) guidelines recommend against RBC transfusion to treat preoperative anemia, except in case of a very low hemoglobin level (<7 g/dL) and insufficient time for alternative treatment due to the urgency of surgery. By comparing IV iron with RBC transfusion, we now know that IV iron is superior to a treatment we should avoid as much as possible, but we do not know whether it truly improves patient outcomes.
In our opinion, the actual research question should be whether IV iron is superior to no treatment of preoperative anemia. Currently, PBM guidelines recommend IV iron as treatment of preoperative anemia, but apart from higher hemoglobin values and RBC less transfusion, convincing evidence that IV iron improves other patient outcomes (eg, less mortality or morbidity) is still lacking.
Our second concern is the high number of patients treated with preoperative RBC transfusion. Despite the well-known association with adverse postoperative outcomes, patients with iron-deficiency anemia were more likely treated with RBC transfusion (n = 127,415) than with IV iron (n = 114,071). Some even to hemoglobin levels >12 g/dL at the day of surgery (approximately 7% according to Table 1). We can only guess why RBC transfusion was used to treat preoperative anemia, as information on the hemoglobin levels at the moment of RBC transfusion is not reported. And third, we wonder which surgical procedures were studied. In Supplementary Table 4, a list of all surgical procedures is reported. Approximately 80% of patients underwent a “vascular introduction and injection procedure” or an “endoscopy procedure on the esophagus”, both nonsurgical procedures. The Current Procedural Terminology (CPT) codes for “vascular introduction and injection procedure,” includes procedures such as “venipuncture and transfusion procedure” and “insertion of central venous access device.” Based on the above, it seems that patients not fulfilling the study inclusion criteria were analyzed. Could it be that nonsurgical patients, such as patients with upper gastrointestinal bleeding, were included? This would, at least in part, explain some of our questions.