**2.3. The diagnostic role of NLR and confounding factors**

Several haematological parameters, including NLR, are significantly higher in gastric cancer patients than in healthy individuals [18]. A number of studies have confirmed that patients affected by gastric carcinoma have significantly higher NLR than healthy controls [16, 17]. NLR was also higher in gastric cancer patients if compared with persons having adenoma or benign gastrointestinal stromal tumour: 2.17 vs. 1.62. Excluding the confounding factors, NLR was an independent predictor of gastric cancer, associated with the odds ratio of 1.446, p = 0.005 [77].

NLR is influenced by smoking [81]. Such differences are reported in gastric cancer patients as well [25] while other researchers have found no difference [47]. Non-oncological diseases, including both inflammations and such frequent non-inflammatory pathologies as diabetes mellitus and atrial fibrillation, among others, can also influence NLR [82]. Thus, SIR should be assessed within the frames of complex patient evaluation.

#### **2.4. Meta-analyses of NLR in gastric cancer**

Several meta-analyses of NLR in gastric cancer have been carried out. Sun et al. have assessed 19 studies of NLR in gastric cancer. They confirmed the association between high NLR and worse overall, progression- or cancer-free survival, and higher stage. The predictive role was lost for stage IV patients who received palliative surgery only [21]. Nineteen studies were subjected to meta-analysis by Xin-Ji et al. [37]. Elevated NLR was associated with shorter overall (odds ratio (OR) 1.65; 95% CI = 1.47–1.83) and shorter cancer-free survival (OR 1.61; 95% CI = 1.28–1.94). Regarding the tumour characteristics, NLR was associated with presence of lymph node metastasis, and high T (T3 + T4) and high stage (III–IV). The odds ratio for lymph node metastasis, 1.70 (95% CI = 1.05–2.75), for T3 or T4 cancer 2.93 (95% CI = 2.27–3.78) and for stage III–IV: 1.87 (95% CI = 1.48–2.35) as reported by Xin-Ji et al. [37]. By meta-analysis performed by Chen et al. [36], high NLR was associated with poor overall survival (hazard ratio (HR) 2.16; 95% CI = 1.86–2.51) and progression-free survival (HR 2.78; 95% CI = 1.95–3.96). In a meta-analysis of 10 studies, higher NLR was associated with worse overall (HR 1.83; 95% CI = 1.62–2.07), progression-free (HR 1.54; 95% CI = 1.22–1.95) and cancerfree (HR 1.58; 95% CI = 1.12–2.21) survival [35].
