The Value Of Procalcitonin In Differential Diagnosis Of Patients With Rheumatic Disease Complicated With Infection

Objective: Because of the wide use of glucocorticoid and immunosup pressants,patients with rheumatic disease are susceptible to various infections.It is difficult to differentiate between disease activity and infection especially when patient complain fever,which is a great challenge for rheumatologists in clinical practice.General inflammatory makers such as erythrocyte sedimentation rate(ESR)and C-reactive protein"(CRP)may be higher in active systemic autoimmune rheumatic diseases as well as in infection,however they do not give much help to differentiation.While bacteria culture could not promptly meet the clinical need.Procalcitonin(PCT)is a biomarker which facilitates recognizing bacterial infections,and more evidences support that it could improve the specificity and sensibility of diagnosis in bacterial infection and benefit for treatment.So in this article,we reviewed relevant literatures of PCT in patients with or without infection,analyzed current evidences regarding PCT in patients with systemic autoimmune rheumatic disease,and highlighted the values of PCT on differential diagnosis in rheumatic diseases complicated with infection.Methods: We screened the PubMed and China National Knowledge Infrastructure(CNKI)to identify literatures including the keywords of "procalcitonin"(PCT)and "connective tissue diseases"(CTD),or "rheumatic disease",coupled with "infection","sepsis","erythrocyte sedimentation rate"(ESR),"C-reactive protein"(CRP)and "autoantibodies".Relevent papers on PCT and systemic autoimmune rheumatic diseases with or without infections were summarized and data were analyzed.Results: Serum PCT is one of the valuble makers of sever systemic bacterial and fugal infections and sepsis.The sensitivity and specificity are53%to100%and84%to97%respectively,which is definitely higher than other inflammatory makers and could not be affected by abnormal renal function or immunosuppressive agents in detection of rheumatic diseases with infection.Most studies suggest that PCT is increasing(PCT≥0.5ng/ml)in systemic lupus erythematosus,systemic vasculitis,arthritis or other rheumatic diseases when complicated with infection,which makes a difference to fifferential diagnosis between recurrence and infection.However,elevated PCT is also found in patients with SLE and active AAV with no evidence of infection,suggesting the limit significance of PCT detection in rheumatic disease.Conclusions: Remarkably elevated PCT is one of the important labor atory indexes with prior sensitivity and specificity for patients with systemic rheumatic disease complicated with systemic infection.The changes of PCT level prove to be valuble for disease assessment and treatment despite of mildly elevated PCT which is actually caused by active rheumatic diseases.So PCT should not replace the other diagnostic methods,and thorough history inquiry,comprehensive physical examination,as well as immunological and microbiological data are equally important.