As apheresis providers, we are very interested in actively collaborating with multidisciplinary care teams that refer patients for our procedures. We read with interest the recently published McMaster RARE-Bestpractices clinical practice guideline on the diagnosis and management of catastrophic antiphospholipid syndrome (CAPS) [1]. However, the clinical practice guideline had several shortcomings that call into question the authors' conclusion that therapeutic plasma exchange (TPE) should be used as first-line therapy. First, the authors do not cite the "Guidelines on the Use of Therapeutic Apheresis in Clinical Practice" as published by the American Society for Apheresis (ASFA) [2]. The ASFA guidelines are published every 2-3 years and describe the use of apheresis in the management of more than 100 disease processes. These guidelines are supported by a current and comprehensive literature review performed by a group of leading apheresis practitioners. The 2013 and 2016 ASFA guidelines categorize CAPS as a category II indication for TPE, meaning that TPE should be part of second-line therapy. The 2013 ASFA guidelines were available when the McMaster RARE-Bestpractices guideline panel convened in 2016, and the 2016 ASFA guidelines were available during the McMaster RARE-Bestpractices clinical practice guideline public comment period. Additionally, the 2016 ASFA guidelines cite 11 articles concerning the management of CAPS, eight of which are not cited in the McMaster RARE-Bestpractices clinical practice guideline [3-10]. All of these articles were available when the McMaster RARE-Bestpractices guideline panel convened in 2016. Second, the authors misrepresent the risks of TPE. The McMaster RARE-Bestpractices guideline cites an article by Shemin et al. andstates that "common adverse effects of plasmapheresis include fever (7.7%), urticaria (7.4%), and symptomatic hypocalcemia (7.3%)" [1,11].The authors are correct that one of the most common side-effects of TPE is symptomatic hypocalcemia, due to the use of citrate anticoagulation in the apheresis circuit. However, the risk of fever and urticaria is almost entirely dependent on the replacement fluid used during a TPE. As stated by Shemin et al., "Fever, chills, or urticaria (all grouped together) was the most common complication, and this was much more common in patients receiving fresh frozen plasma (FFP) as replacement fluid" [11]. Urticaria occurred in 16.8% of patients receiving FFP as replacement fluid, whereas urticaria occurred in 0.2% of patients receiving albumin/normal saline as replacement fluid [11]. Urticaria and fever are common transfusion reactions; unsurprisingly, these occur when plasma products are used as TPE replacement fluid. Thus, fever and urticaria in the context of TPE are commonly attributable to plasma products, rather than the TPE itself. Further, the authors state that "adverse events occurred in 36% of all patients." This is inaccurate, as Shemin et al. state, "Of the 1727 total treatments, 614 (36%) involved some complication." Thus...