Xu S, Liang Y, Wang J, et al. - Via a case-control study of 61 patients diagnosed lumbar spinal stenosis (LSS) with RA (RA group) and 87 matched patients without RA (NRA group), experts contrasted intraoperative bleeding, drainage, and hidden blood loss (HBL) of posterior lumbar interbody fusion on LSS in patients with RA and non-RA and recognized the risk factors of HBL with RA. No statistical variation in total blood loss (TBL), intraoperative blood loss, and postoperative drainage while HBL and the proportion of HBL in TBL were lower in the NRA group was noted. Stratified analysis on the basis of the number of surgical levels recommended HBL and the proportion of HBL in the NRA group was better in long-segment surgery (> 2 segments). The secondary outcomes exhibited the alterations of the Hct was lower in the NRA group but not the decrease of Hb. Moreover, no notable variation in neoformative and grade-aggravated anemia, as well as the number of allogeneic blood transfusion was observed and operation time exhibited Steinbroker classification, disease-modifying anti-rheumatic drugs (DMARDs), the variance of Hb and allogeneic blood transfusion were risk factors for HBL with RA. Thus, no variation in TBL, intraoperative bleeding, and operation time, but HBL was greater in RA patients especially in long-segmental operation. Further, for HBL in RA patients, Steinbroker classification, DMARDs, the variance of Hb, and allogeneic blood transfusion were independent risk factors.