Objective To observe the effect of nutritional status variation on hidden blood loss in elderly patients with intertrochanteric fracture treated with proximal femoral nail antirotation (PFNA).Methods Ninety-six elderly patients with femoral intertrochanteric fracture aged 72-94 years [mean,(78.7 ± 9.5) years] were submitted to closed reduction and PFNA internal fixation.According to the mini nutritional assessment (MNA) score,the patients were randomized into normal-nourishment group (n =26),potentially malnourishment group (n =32) and malnourishment group (n =38).Correlation between MNA score and serological examination was analyzed.Total blood loss and hidden blood loss were calculated depending on height,weight,intra-operative blood loss,post-operative blood loss,preand post-operative Hct,and blood transfused.According to the mean hidden blood loss,patients were divided into low (n =51) and high (n =45) hidden blood loss groups.Relationship among high hidden blood loss,MNA score,and serological examination was evaluated.Results Preoperative MNA score showed strong correlation with nutritional evaluation results assessed by serological examination,and the detection effectiveness of malnutrition by albumin (ALB),prealbumin (PA),transferrin (TRA),and T lymphocyte percentage (TLP) was better than that by total protein (TP),total lymphocyte count (TLC) and hemoglobin (Hb).Nutritional status was further deteriorated after PFNA in patients with malnutrition.Forty-five patients were found to have high hidden blood loss.Incidence of high hidden blood loss revealed significant difference among groups (P ＜ 0.05).Preoperative incidence of hidden blood loss assessed by ALB,PA,TRA,TLP and Hb in high hidden blood loss group was obviously higher than that in low hidden blood loss group.Postoperative incidence of hidden blood loss assessed by the serological examination in high hidden blood loss group was evidently higher than that in low hidden blood loss group as well as higher than the preoperative results.Preoperative MNA score,ALB,PA,TRA,TLP and Hb showed strong correlations with high hidden blood loss (r =0.4-95,0.4-80,0.4-71,0.502,0.367 and 0.309,respectively,P ＜ 0.05).Conclusions Total blood loss,hidden blood loss and incidence of high hidden blood loss are gradually increased with the deterioration of nutritional status.MNA score and serological examination (ALB,PA,TRA,TLP and Hb) have significant values in predicting the risk of high hidden blood loss.