TABLE 2

Studies investigating relationships between neutrophil to lymphocyte ratio (NLR) and other biomarkers in chronic obstructive pulmonary disease (COPD)

First author [ref.]Main markers investigatedMain findings
Günay [36]CRP, PDW, RDW, MPVIncreased levels of WBC, CRP, RDW and MPV in COPD. Significant positive correlation of NLR with CRP and RDW, and negative correlation with MPV in COPD
Furutate [37]CRPCRP significantly increased in COPD. Significant positive correlation between NLR and CRP
Taylan [39]CRP, WBC, RDW, PDW, MPV, ESRSignificant correlations with CRP, WBC and ESR. High NLR values in AECOPD patients with low CRP, WBC or ESR levels
Farah [40]CRP, WBC, RDW, MPV, CD64RDW, CRP and CD64 significantly elevated in AECOPD. Significant correlations of NLR with CRP and RDW
Kurtipek [41]CRP, PLRCRP and PLR are significantly higher in AECOPD. Significant positive correlation with CRP. CRP AUC was better than that of NLR, which was better than AUC for PLR
Bilir [42]CRPSignificant positive correlation with CRP. CRP AUC better than AUC for NLR
In [43]CRP, ESRSignificant positive correlation with CRP and ESR
Tanriverdi [44]CRP, PCTPCT higher in infections. Significant but weak positive correlation with CRP. AUC value of PCT significantly better in predicting bacterial infection compared with the CRP or the NLR
van de Geijn [45]CRP, PCT and othersCRP and PCT higher in AECOPD, especially bacterial ones. Addition of PCT to CRP increased specificity for bacterial AECOPD compared to CRP alone
Yasar [47]CRP, RDW, MPV, PDWCRP, RDW and PDW were higher while MPV was lower in COPD. CRP, RDW and PDW were higher and MPV was lower in patients who had metabolic syndrome
Lee [49]CRPCRP was higher in exacerbations than in healthy controls
Duman [50]CRP, platelet/MPVCRP was significantly higher in the non-eosinophilic group. The platelet/MPV ratio was not different between the two groups. Survival negatively influenced by elevated CRP in the non-eosinophilic group
Rahimirad [51]dNLR, MLR, PLRdNLR higher in dead patients than in those discharged alive. MLR and PLR not significant in multivariate analysis
Yao [52]CRP, PLRNLR levels correlated with serum CRP levels in AECOPD. CRP and PLR levels higher in dead patients than in survivors. CRP AUC higher than that of PLR in predicting death
Xiong [53]ESR, EBR, CRP, RDWEBR higher in COPD than in controls, and in survivors than in dead patients. EBR and CRP are predictors of mortality, not ESR or RDW
Kumar [54]PLR, ureaPLR significantly associated to 90-days mortality, AUC poor
Saltürk [55]CRP, platelet/MPVCRP >50 mg·mL−1 risk factor for mortality
Sørensen [56]Calprotectin, YKL-40Correlation with calprotectin. In the group not treated with systemic glucocorticoids, plasma calprotectin was significantly associated with mortality. In the group treated with systemic glucocorticoids, higher plasma YKL-40 was significantly associated with mortality

CRP: C-reactive protein; PDW: platelet distribution width; RDW: red cell distribution width; MPV: mean platelet volume; WBC: white blood cell; ESR: erythrocyte sedimentation rate; PLR: platelet to lymphocyte ratio; PCT: procalcitonin; dNLR: derived neutrophil to lymphocyte ratio; MLR: monocyte to lymphocyte ratio; EBR: eosinophil to basophil ratio; AECOPD: acute exacerbation of COPD; AUC: area under the curve.