Serum Neutrophil Gelatinase-Associated Lipocalin Levels in Acute Brucellosis and Brucellar Spondylodiscitis

Abstract

Brucellosis is a zoonotic infectious disease caused by Brucella spp., an intracellular bacterium. The complications of acute Brucellosis may affect all organs and systems. The most common complication of the disease is musculoskeletal system involvement. The neutrophil gelatinase-associated lipocalin (NGAL) is a marker of neutrophil formation and acts as a siderophore-binding protein to prevent bacterial iron uptake and its use as a marker in the diagnosis and follow-up of bacterial infections is being investigated. The aim of this study was to measure the serum levels of NGAL in patients with acute Brucellosis and Brucellar spondylodiscitis, and to determine whether there is a correlation between NGAL levels and the progression and complications of the disease. This prospective case control study was conducted with 240 patients and 120 healthy controls. The diagnosis of acute Brucellosis was established when a person was asked to take an STA test due to clinical symptoms within the past eight weeks, and the test result that exceeded 1/160, or a 4-fold titer increase was found in the STA test after an interval of two weeks, and/or there was Brucella spp. growth in the blood culture. A contrasted lumbar magnetic resonance (MR) scan was performed on patients diagnosed with acute Brucellosis who had lower back pain. Presence of spondylodiscitis was assessed radiologically with contrasted lumbar MR images. NGAL levels were determined with ELISA assay. The median NGAL value was found to be 456.67 ng/L (101.41-5804.41 ng/L) in patients with acute Brucellosis and 113.84 ng/L (58.29-542.34 ng/L) in the control group. The median NGAL value was statistically higher in the patients than the control group (p= 0.001). Brucellar spondylodiscitis was detected in 57 (23.7%) of 240 patients diagnosed with acute Brucellosis. The median NGAL value was 1885.62 ng/L (143.21-5804.41 ng/L) in patients with Brucellar spondylodiscitis, and 356.87 ng/L (101.41-1874.07 ng/L) in those who did not have Brucellar spondylodiscitis. This difference was statistically significant (p= 0.001). Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) values were found to be higher in patients who had Brucellar spondylodiscitis. Blood cultures were drawn from 186 (77.5%) of the 240 patients diagnosed with acute Brucellosis. The blood culture positivity rate was 36.02%. Patients whose blood cultures were positive had higher NGAL levels (p= 0.001). The blood culture positivity rate was higher in patients who were diagnosed with Brucellar spondylodiscitis (p= 0.001). A regression analysis showed that female gender and high levels of NGAL, ESR, and alanine aminotransferase (ALT) could be used as predictors of Brucellar spondylodiscitis. The explanatoriness of the model was 82.3%. Although determination of NGAL levels is seen as a useful marker in the diagnosis of acute Brucellosis and predicting the presence of Brucellar spondylodiscitis, more comprehensive studies are required to be used in clinical practice in regions where Brucellosis is endemic.