title: Effect of Depth of Centrifuged Synovial Fluid on Leukocyte Esterase Test for Periprosthetic Joint Infection.
abstract: Centrifugation of aspirated synovial fluid before leukocytes esterase (LE) testing for diagnosing periprosthetic joint infection (PJI) may make blood tinged specimens interpretable. We aimed to establish the proper sampling depth of centrifuged specimens for LE testing as one diagnostic criterion and also AS-D chloroacetate esterase (CAE) staining testing as an adjunctive tool. A definite PJI knee joint group and an aseptic primary total knee arthroplasty control group were studied quasi-experimentally (N = 46). At 2,000 g for 15 min, 3 ml of synovial fluid was centrifuged. LE strip testing and median synovial WBC count were performed at 2, 4, and 6 mm depths. CAE staining test characterized LE particles. ROC curve, area under the curve, and significant differences were determined. The proper predictive depth to diagnose PJI was sought by forward stepwise logistic regression. All fresh blood-tinged specimens had uncertain interpretations. Centrifugation increased interpretability (55-100%). ROC curve and area under the curve at 2, 4, and 6 mm depths were 0.822, 0.804, and 0.786, respectively. The cut point of ++ to diagnose PJI was statistically significant (p < 0.05) at all depths. p-values of forward stepwise logistic regression at 2, 4, and 6 mm were 0.001, 0.752, and 0.756, respectively. CAE staining confirmed extracellular LE release by polymorphonuclear neutrophils (PMN). A specimen at <2 mm from the surface of centrifuged synovial fluid at a grading of ++ or more for PJI diagnosis is proper for LE testing. CAE staining testing adjunctively characterizes LE particles and cell morphology. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2545-2550, 2017.
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, Siriraj Hospital, Mahidol University, 2 Wanglang Rd Bangkoknoi, Bangkok, 10700, Thailand.
authors.forename: Pakpoom
authors.initials: P
authors.lastname: Ruangsomboon
authors.affiliation: Division of Hematology, Department of Medicine, Faculty of Medicine, Siriraj Hospital, Mahidol University, 2 Wanglang Rd Bangkoknoi, Bangkok, 10700, Thailand.
authors.forename: Sriprapa
authors.initials: S
authors.lastname: Chinprasertsuk
authors.affiliation: Department of Clinical Pathology, Faculty of Medicine, Siriraj Hospital, Mahidol University, 2 Wanglang Rd Bangkoknoi, Bangkok, 10700, Thailand.
authors.forename: Varanya
authors.initials: V
authors.lastname: Khejonnit
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, Siriraj Hospital, Mahidol University, 2 Wanglang Rd Bangkoknoi, Bangkok, 10700, Thailand.
authors.forename: Keerati
authors.initials: K
authors.lastname: Chareancholvanich
mesh_terms: D000368:Aged; D002265:Carboxylic Ester Hydrolases / Q000032:analysis*; D004796:Clinical Enzyme Tests / Q000379:methods*; D005260:Female; D006801:Humans; D007595:Joint Prosthesis; D008297:Male; D008875:Middle Aged; D016459:Prosthesis-Related Infections / Q000175:diagnosis*; D013582:Synovial Fluid / Q000201:enzymology*
chemical_list: C021443:leukocyte esterase; D002265:Carboxylic Ester Hydrolases
keywords: centrifuged; leukocytes esterase test; naphtol AS-D choloroacetate esterase staining; periprosthetic joint infection; synovial fluid