Baseline peripheral blood neutrophil-to-lymphocyte ratio could predict survival in patients with adult polymyositis and dermatomyositis: A retrospective observational study

Abstract

Recent studies have suggested that neutrophil-to-lymphocyte ratio (NLR) and C-reactive protein-to-albumin ratio (CAR) are emerging markers of disease activity and prognosis in patients with chronic inflammatory diseases, cardiovascular diseases, or malignancies. Therefore, we investigated the clinical significance and prognostic value of the NLR and CAR in adult patients with polymyositis and dermatomyositis. The medical records of 197 patients with newly diagnosed polymyositis/dermatomyositis between August 2003 and November 2016 were retrospectively reviewed. Survival and causes of death were recorded during an average 33-month observational period. Clinical and laboratory findings were compared between survivors and non-survivors. Using receiver operating characteristic curves, the NLR and CAR cut-off values for predicting survival were calculated. Univariate and multivariate analyses using Cox proportional hazard models were performed to identify factors associated with survival. Twenty-six patients (13.2%) died during the study period, and the 5-year survival-rate was estimated to be 82%. The non-survivor group exhibited older age and a higher prevalence of interstitial lung disease (ILD), acute interstitial pneumonia, and acute exacerbation of ILD compared to that in the survivor group. NLR and CAR values were significantly higher in the non-survivors and in patients with polymyositis/dermatomyositis-associated ILD, and the death rates increased across NLR and CAR quartiles. Furthermore, when stratified according to the NLR or CAR optimal cut-off values, patients with a high NLR (>4.775) or high CAR (>0.0735) had a significantly lower survival rate than patients with low NLR or CAR, respectively. In addition, old age (>50 years), the presence of acute interstitial pneumonia, hypoproteinemia (serum protein <5.5 g/dL), and high NLR (but not high CAR) were independent predictors for mortality. The results indicate that a high NLR is independently associated with worse overall survival. Thus, the baseline NLR level may be a simple, cost-effective prognostic marker in patients with polymyositis/dermatomyositis.

Fig 1. The distribution of non-survivors based on the quartiles of absolute neutrophil and lymphocyte counts, and serum CRP and albumin levels in patients with polymyositis/dermatomyositis.

The prevalence of non-survivors increased across quartiles for absolute neutrophil count (ANC, A), and decreased across quartiles for absolute lymphocyte count (ALC, B). Consequently, the prevalence of non-survivors was the largest in the highest quartile of the neutrophil/lymphocyte ratio (NLR, C). Also, the prevalence of non-survivor increased with increasing quartiles of C-reactive protein (CRP, D), and with lower quartiles for albumin (E). Consequently, the distribution of non-survivors was significantly different among CRP/albumin ratio (CAR) quartiles (F). P values were calculated by chi-square test.

Fig 2. The neutrophil/lymphocyte ratio (NLR) and CRP/albumin ratio (CAR) according to clinically relevant subgroups.

The NLR (A and B) and CAR (C and D) were significantly higher in the non-survivor group (versus the survivor group) and in patients with interstitial lung disease (ILD, versus those without ILD). Additionally, among patients with ILD, patients suffering an acute exacerbation (AE) of ILD had significantly higher NLR and CAR values. However, the presence of acute interstitial pneumonitis (AIP) was only associated with the NLR. Bars represent the standard error of the mean, and P values were calculated by the t-test.

Fig 3. Receiver operator characteristic curves for predicting non-survival in patients with idiopathic inflammatory myopathy.

NLR, neutrophil-to-lymphocyte ratio; CRP, C-reactive protein; CAR, CRP-to-albumin ration; AUC, area under the curve; CI, confidence interval.

Fig 4

Survival curves for overall survival in patients with idiopathic inflammatory myopathy, stratified by low/high NLR (A) and CAR (B). NLR, neutrophil-to-lymphocyte ratio; CRP, C-reactive protein; CAR, CRP-to-albumin ratio.