Background: The significance of low plasma neutrophil gelatinase-associated lipocalin (NGAL) level in systemic inflammation has not been investigated. The aim of this study was to investigate low plasma NGAL level in systemic inflammation and its relationship with proinflammatory cytokines, procalcitonin (PCT), leukocyte profiles, nutritional status, and kidney function.
Methods: Patients with systemic inflammation were evaluated by measuring NGAL, PCT, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), high-sensitivity C-reactive protein (hsCRP), serum creatinine (sCr), and clinical scores.
Results: Of 191 patients, 30 (15.7%) had low NGAL levels (< 68 ng/mL), and 102 (53.4%) had elevated NGAL levels (> 150 ng/mL). Among the 30 patients with low NGAL levels, 26 (86.7%) had normal kidney function and 24 (80.0%) had low-grade inflammation. In comparison with healthy individuals, patients with low NGAL levels had higher levels of TNF-α, IL-6, PCT, and hsCRP but not absolute neutrophil count (ANC). Neutropenia was more often observed in subjects with low NGAL levels than in those with elevated NGAL levels (16.7% versus 1.9%, p < 0.001). In the low NGAL group, plasma NGAL was significantly associated with ANC (r = 0.312, p < 0.001) but not cytokines, sCr, nutritional parameters, and clinical scores. Receiver operating characteristic (ROC) curve analysis demonstrated that the diagnostic ability of the ANC for identifying low NGAL levels was superior to that of PCT and TNF-α [0.82 (95% CI, 0.75 - 0.89) versus 0.67 (95% CI, 0.56 - 0.79) and 0.66 (95% CI, 0.54 - 0.78), respectively, p < 0.001].
Conclusions: Low plasma NGAL level in systemic inflammation was more closely linked to the non-increment of the ANC than proinflammatory cytokines, PCT, and nutritional status, particularly in patients with low-grade inflammation who had preserved kidney function.