Abstract: Objective To study the correlation of peripheral blood CD4+/CD8+, human neutrophil gelatinase-associated lipocalin (NGAL) and serum amyloid A protein (SAA) to bacterial infection and their diagnostic value in elderly patients with chronic renal failure (CRF) undergoing maintenance hemodialysis (MHD).  Methods  This was a cross-sectional study, which enrolled the elderly CRF patients treated with MHD in the hospital between October 2019 and October 2021. They were divided into infected group (n=61) and non-infected group (n=104) according to the presence or absence of bacterial infection. Blood CD4+/CD8+, NGAL and SAA were measured and compared between the two groups. Logistic regression model was established to analyze the relationship between the three blood indicators and bacterial infection in elderly CRF patients undergoing MHD. Receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of the three blood indicators.  Results  In infected group, CD8+ (28.54±2.48% vs. 27.61±2.09%, t=2.573, P=0.011), NGAL [(203.85±39.46)ng/ml vs. (149.71±26.84)ng/ml, t=6.670, P<0.001] and SAA [(21.83±4.75)ng/ml vs. (15.37±3.38)ng/ml, t=10.116, P<0.001] were higher, while CD4+ [(38.27±4.86)% vs. (45.18±5.13)%,    t=8.514, P<0.001] and CD4+/CD8+ (1.26±0.42 vs. 1.57±0.53, t=3.904, P<0.001) were lower, as compared with those in non-infected group. After adjusting age, gender and dialysis age (The dependent variable assignment was set at 1 in infected group and at 0 in non-infected group), logistic regression results showed that CD4+/CD8+ (OR=0.586, 95% CI: 0.440～0.780, P<0.001), NGAL (OR=1.324, 95% CI: 1.149～1.525, P<0.001) and SAA (OR=1.419, 95% CI: 1.251～1.610, P<0.001) were closely related to bacterial infection in elderly CRF patients undergoing MHD (P<0.05). Receiver operating characteristic (ROC) curve displayed that the area under curve (AUC) values of CD4+/CD8+, NGAL and SAA for the diagnosis of bacterial infection were 0.576, 0.738 and 0.838 respectively, with the sensitivities of 54.10%, 62.30% and 77.05% respectively, and the specificities of 63.46%, 83.65% and 77.88% respectively. Logistic regression model for comprehensive application of the three indicators was established and showed the AUC, sensitivity and specificity were 0.886, 85.25% and 79.81% respectively.  Conclusion  In elderly CRF patients undergoing MHD, the levels of peripheral blood CD4+/CD8+, NGAL and SAA were closely related to bacterial infection. Therefore, assays of CD4+/CD8+, NGAL and SAA can provide references for accurate and early diagnosis of bacterial infection.

Key words: Hemodialysis, Bacterial infection, CD4+/CD8+, Human neutrophil gelatinase-associated lipocalin, Amyloid A protein