Considering the great success of joint arthroplasty, the number of patients receiving joint arthroplasty has increased year by year. At the same time, researchers estimated that the incidence of Hip and Knee Arthroplasty revision surgery in the United States is projected to increase to 2030 . In 2017, papers published by Delanois et al and Gwam et al showed that PJI is the most common reason for revision in total knee arthroplasty patients  and the fourth most common reason for revision in total hip arthroplasty patients in the United States . Although one stage or two stage revision surgery combined with antibiotics treatment exert excellent clinical effect, it is still not easy to make a prompt and accurate PJI diagnosis, PJI diagnosis remains challenging.
Despite numerous efforts have been tried to increase the accuracy of PJI diagnosis, until now, there is still no consensus on the superiority of one method better than another. Compared with other methods, blood examination, which has the merit low-risk, non-invasion and rapidity, is always the first screening option for clinicians to make a PJI diagnosis. Though CRP and ESR are still widely used as first-line screening markers for PJI, they are non-specific blood inflammatory markers and could be influenced by many factors . So, lots of researchers are trying to evaluate the meaning of some other blood markers in PJI diagnosis.
Despite coagulation markers such as Platelet Count and Mean Platelet Volume ratio , D-Dimer  and plasma Fibrinogen have been used in inflammation and infection diseases diagnosis [10, 11], the role of these coagulation markers in PJI diagnosis is still unknow. Although the role of D-Dimer [12–14]、plasma Fibrinogen , Platelet Count and Mean Platelet Volume ratio were evaluated in PJI diagnosis, and D-dimer > 1170 ng/m, PC/MPV > 31.70 and FIB > 4.01 µg/mL were recommend as the optimum threshold value for the PJI diagnosis, no subsequent studies were published thereafter.
In this study, we retrospectively analyzed the sensitivity and specificity of serum CRP, ESR, Platelet Count and Mean Platelet Volume ratio (PC/MPV), plasma D-Dimer and Fibrinogen in PJI diagnosis. Similar with Li’s  study, we found that plasma Fibrinogen can be used for as a new marker for PJI diagnosis. However, different from Paziuk T et al’s and Qin et al’sstudy, our data demonstrated that PC/MPV and D-Dimer should not be selected as the first option for PJI diagnosis. But we think our conclusion still make sense and the reasons are: 1, we take the MSIS criterion which recommend ESR༞30 mm/h,CRP༞10 mg/L other than Paziuk’s ESR༞46 mm/h༌CRP༞1.5 mg/L as the optimum threshold value for PJI diagnosis; 2, consistent with Guangxu et al’s study and Cheng et al’s study, we again showed that plasma D-dimer has limited performance for the diagnosis of PJI. As a result, our conclusion performs better than Paziuk et al’s and Qin et al’s in clinical utilization.