Value Of Platelet-to-lymphocyte Ratio(PLR) In Predicting Disease Activity And Severity In Rheumatoid Arthritis: A Retrospective Study

Objective:This study aimed to study the value of blood routine parameters as makers in predicting the disease activity and severity in patients with rheumatoid arthritis(RA).Methods:(1)A total of 139 inpatients with rheumatoid arthritis(RA)who were hospitalized in the Department of Rheumatology,the second xiangya hospital of central south university from July 1,2016 to August 30,2019 were enrolled as the derivation cohorts.The characteristics of clinical data were retrospectively analyzed.Then,clinical indices,especially focus on blood routine parameters(hemoglobin [Hb],neutrophil [N],lymphocyte[L],platelet [PLT],red blood cell distribution width [RDW],mean platelet volume [MPV],Neutrophil/lymphocyte ratio [NLR] and platelet/lymphocyte ratio [PLR]),and joint ultrasound score(gray-scale ultrasound score [GS-US],Power Doppler ultrasound score [PD-US],total ultrasound score [T-US])were compared between different disease activity groups.Then,Pearson correlation analysis and Logistic regression analysis were used to analyze the correlation between blood routine parameters with DAS28 score and joint ultrasound score,in order to finding out the predictor factors of DAS28 score and ultrasound score from blood routine parameters.Finally,receiver operating characteristic curve(ROC)analysis was performed to compare the efficacy of blood routine parameters,erythrocyte sedimentation rate(ESR)and C-reactive protein(CRP)in evaluating disease activity and severity in RA.(2)A total of 127 RA outpatients who treated in the Department of Rheumatology,the second xiangya hospital of central south university from July 1,2021 to October 30,2021 were selected as the validation cohorts.To verify the clinical significance of the above-mentioned blood routine parameters with predictor factors in patients with different disease activity,ROC curve analysis was performed to compare the blood routine parameters,ESR and CRP in reflecting disease activity,so as to assess clinical value of the blood routine parameters.Results:(1)Results of a study of 139 hospitalized RA patients(derivation cohort)showed:(1)All 139 hospitalized RA patients were divided into two groups according to their disease activity: 49 patients with moderate disease activity(MDA-RA)and 90 patients with high disease activity(HDA-RA).There were no significant differences in joint function score,swollen joint count(SJC),tender joint count(TJC),physician global assessment(PGA),ESR,CRP and blood routine parameters,including Hb,L,Plt,NLR and PLR between two groups were statistically significant,and the differences of joint ultrasound score including PD-US score and T-US score were statistically significant.(2)Correlation analysis of blood routine parameters and disease activity score were performed.Pearson correlation analysis showed that there was significant correlation between Hb,L,Plt,MPV,NLR,PLR and DAS28-ESR,meanwhile Hb,L,Plt,NLR,PLR were significantly correlated with DAS28-CRP.The results of Logistic regression analysis between PLR with DAS28-ESR and DAS28-CRP indicted that PLR was an independent predictor factors for RA disease activity.(3)Correlation analysis of blood routine parameters and ultrasound scores were conducted.Pearson correlation analysis showed that there was significant correlation between Plt,NLR,PLR and PD-US scores,meanwhile Plt,PLR were significantly correlated with T-US scores.There was no blood routine parameter significantly correlated with GS-US scores.The results of Logistic regression analysis between PLR with PD-US scores and T-US scores indicted that PLR was an independent predictor factors for RA severity.(4)ROC analysis showed that PLR could effectively predict the level of DAS28-ESR(AUROC=0.734)and DAS28-CRP(AUROC=0.718).At the same time,PLR could also predict the severity of PD-US(AUROC=0.789)and T-US(AUROC=0.799).Moreover,the efficacy,sensitivity and specificity of PLR alone in predicting disease activity and severity were similar to those of combined use of ESR and / or CRP.(5)Depending the value of cut off about PLR as 236.6,all RA patients were divided into low PLR group and high PLR group.There were significant differences in SJC,ESR,CRP,DAS28-ESR,DAS28-CRP,PDUS scores and T-US scores between the two groups,indicating that PLR alone could effectively predicting the disease activity and severity of RA inpatients.(2)Results from a study of 127 outpatient RA patients(validation cohort)showed:(1)All 127 outpatient RA patients were divided into three groups according to their disease activity score: low disease activity group(LDARA),moderate disease activity group(MDA-RA)and high disease activity group(HAD-RA).Between different degrees of disease activity RA patients,there were statistically significant differences in PGA,ESR,CRP and blood routine parameters,including Hb,L,Plt,MPV,NLR and PLR.(2)Pearson correlation analysis showed that: Hb,L,Plt,MPV,NLR,PLR were significantly correlated with DAS28-ESR and DAS28-CRP;The results of Logistic regression analysis indicted that PLR was an independent predictor factors for RA disease activity(DAS28-ESR and DAS28-CRP).(3)ROC analysis showed that: PLR could effectively predict low /(moderate + high)DAS28-ESR(AUROC=0.834)and DAS28-CRP(AUROC=0.818);At the same time,PLR could also predict(low +moderate)/ high DAS28-ESR(AUROC=0.759)and DAS28-CRP(AUROC=0.701).Moreover,the efficacy,sensitivity and specificity of PLR alone in predicting disease activity were similar to those of combined use of ESR and / or CRP.(4)Taking 182.6 and 240.1 as the cut-off value of PLR,the patients were divided into low PLR group,medium PLR group,and high PLR group.There were statistical differences in SJC,TJC,PGA,ESR,CRP,DAS28-ESR,DAS28-CRP between the three groups,indicating that PLR alone could better evaluate the disease activity of RA outpatients.Conclusion:(1)In hospitalized RA patients(derivation cohort),blood routine parameters Plt,PLR,and NLR were significantly correlated with DAS28 score of disease activity and ultrasound score of severity(PD-US and TUS);Among them,PLR was an independent predictor factor indicating moderate to high disease activity and severity.The efficacy of PLR alone in predicting moderate and high disease activity and severity is not inferior to that of ESR and CRP.The best cut-off value of PLR as 236.6 could better distinguish between moderate and high disease activity and different severities.(2)In RA outpatients(validation cohort),blood routine parameters Hb,L,Plt,MPV,NLR,PLR were significantly correlated with the DAS28 score of disease activity;PLR was indicative of different degrees of disease activity of disease active RA.As an independent predictor factor,PLR can better predict different disease activity when used alone,and its efficacy is not inferior to ESR and CRP.The best cut-off value of PLR as 182.6 could distinguish between low disease activity and moderate-high disease activity better.The cut-off value of PLR as 240.1 could better distinguish low-moderate disease activity RA from high disease activity RA.Finally,the clinical significance of blood routine parameters in predicting disease activity and severity was clarified through the consistency of RA inpatients(derivation cohort)and RA outpatients(validation cohort).PLR can be used as a reliable indicator to predict RA patients with different disease activity,the cut-off values for predicting low,medium and high disease activity are 182.6 and 240.1.The potential of PLR to indicate the severity of disease requires more musculoskeletal ultrasound data of RA patients to confirm.