Albumin to Globulin ratio, Neutrophil to Lymphocyte ratio, and Globulin levels do not outperform ESR or CRP when diagnosing periprosthetic joint infection

OBJECTIVE: To evaluate the relative performance of clinical readouts including serum C-reactive protein (CRP) levels, the erythrocyte sedimentation rate (ESR), globulin (GLB) levels, the albumin to GLB ratio (A/G), and the neutrophil to lymphocyte ratio (NLR) when diagnosing periprosthetic joint infection (PJI). METHODS: Clinical data was collected from 115 individuals diagnosed in our department between January 2017 and December 2020 with either chronic PJI (29 female, 24 male; median age 71.00 years [range, 41–94 years]) or aseptic loosening (30 female, 32 male; median age 68.50 years [range, 34–85 years]). Patient demographic data were compared, and the relative sensitivity and specificity of preoperative GLB, ESR, CRP, NLR, and A/G values as predictors of PJI diagnosis were assessed. RESULTS: Median globulin levels in the PJI and aseptic groups were 31.700 g/L (interquartile range [IQR], 28.400—35.300) and 26.600 g/L (IQR, 24.375—30.550), respectively (p < 0.001). The median A/G values in the PJI and aseptic groups were 1.150 (IQR, 0.960—1.255) and 1.510 (IQR, 1.265—1.670), respectively (p < 0.001). The median NLR values in the PJI and aseptic groups were 2.510 (IQR, 1.900—3.335) and 1.850 (IQR, 1.425 to 2.362), respectively (p < 0.001). The median ESR values in the PJI and aseptic groups were 53.000 mm/h (IQR, 35.000—76.500) and 16.000 mm/h (IQR, 7.000—33.000), respectively (p < 0.001). Median CRP levels in the PJI and aseptic groups were 24.890 mg/L (IQR, 10.595—54.095) and 2.245 mg/L (IQR, 0.865—8.6075), respectively (p < 0.001). Area under the receiver operating characteristic (ROC) curve (AUC) values for CRP, ESR, GLB, A/G, and NLR were 0.841 (95% confidence interval, 0.761–0.903), 0.850 (0.771–0.910), 0.747 (0.658–0.824), 0.779 (0.692–0.851), and 0.708 (0.616–0.789), respectively. When GLB > 26.6 g/L, A/G < 1.32, and NLR > 2.1 were utilized as threshold values to diagnose PJI, GLB and A/G were found to exhibit superior sensitivity (90.57%, 81.13%) to that observed for CRP (71.70%) and ESR (79.25%), but the specificity of these two metrics (GLB: 51.61%, A/G: 72.58%) was significantly reduced relative to that for CRP (87.10%) or ESR (75.81%). ROC analyses further revealed that NLR did not exhibit significant advantages in sensitivity (73.58%) or specificity (70.97%) relative to CRP or ESR. CONCLUSION: Globulin levels, NLR values, and A/G values do not outperform ESR or CRP levels when used to diagnose PJI. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12891-022-05357-y.