Objective: To investigate the diagnostic efficacy of silkworm larvae plasma (SLP) colorimetry in the accurate diagnosis of periprosthetic joint infection (PJI).
Methods: Ninety healthy male New Zealand white rabbits were used for knee arthroplasty with Swanson prosthesis. Then they were randomly divided into 3 groups according to different pathogenic bacteria: group A ( Staphylococcus aureus group), group B ( Staphylococcus epidermidis group) and group C ( Escherichia coli group), with 30 rats in each group. The PJI model was prepared by knee injection with 1 mL of pathogenic bacteria of different concentrations. Samples were taken before inoculation and at 7, 14, and 21 days after inoculation, and based on the 2018 PJI Philadelphia International Consensus diagnostic criteria, the success rate of modeling among 3 groups of experimental animals was determined. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic efficiency of SLP colorimetry were calculated.
Results: At 21 days after inoculation, 26, 18, and 23 rabbits in groups A, B, and C were diagnosed as infection, respectively. The success rates of modeling were 86.7%, 60.0%, and 76.7%, respectively, showing no significant difference among the 3 groups ( χ 2=5.724, P=0.073). The results of PJI colorimetry showed that 1 false-positive animal (specificity 75.0%) appeared in group A at 7 days, and the specificity of SLP increased to 100.0% over time (on 14 and 21 days); on 14 and 21 days, another animal appeared false-negative results (sensitivity decreased from 100.0% to 96.2%). One false-positive animal appeared in group B at 7 days (specificity 91.7%), the specificity returned to 100.0% over time; 1 and 4 false-negative animals appeared at 14 and 21 days, respectively (sensitivity 94.4% and 83.3%, respectively). In group C, two false-positive animals (specificity 71.4%) were found at 7 days, and then returned to 100.0%. The diagnostic efficiency of groups A and C was very high at 21 days (96.7% and 100.0%), even for the low virulence Staphylococcus epidermidis in group B, the diagnostic efficiency could be maintained at 90.0% (21 days), and the overall diagnostic efficiency was very good (95.6%).
Conclusion: SLP colorimetry has high sensitivity, specificity, and diagnostic efficiency in the diagnosis of PJI, which is a potential diagnostic method.
目的: 探讨蚕蛹浆（silkworm larvae plasma，SLP）比色法在关节假体周围感染（periprosthetic joint infection，PJI）精准诊断中的应用价值。.
方法: 取90只健康雄性新西兰大白兔，采用Swanson假体行膝关节置换手术；然后根据致病菌不同随机分为3组：A组（金黄色葡萄球菌组）、B组（表皮葡萄球菌组）及C组（大肠埃希菌组），每组30只。术后第3天膝关节腔内注射1 mL不同浓度致病菌制备PJI模型。分别于接种菌液前及接种后7、14、21 d取样进行检测，参照2018年PJI费城国际共识诊断标准首先判定并计算3组实验动物的造模成功率，并采用SLP比色法计算其在PJI精准诊断中的敏感性、特异性、阳性预测值、阴性预测值和诊断效率。.
结果: 接种菌液21 d时，A、B、C组分别有26、18、23只实验动物诊断为感染，造模成功率分别为86.7%、60.0%、76.7%，3组间比较差异无统计学意义（ χ 2=5.724， P=0.073）。PJI比色法结果显示，A组在7 d时出现1只假阳性动物（特异性75.0%），随时间推移（14、21 d）SLP的特异性升至100.0%；14、21 d，另出现了1只假阴性动物（敏感性由100.0%降至96.2%）。B组在7 d时出现1只假阳性动物（特异性91.7%），随着时间推移特异性回升至100.0%；在14、21 d时分别出现1只和4只假阴性动物（敏感性分别为94.4%及83.3%）。C组在7 d时有2只假阳性动物（特异性71.4%），随后回升至100.0%。A、C组在21 d时诊断效率极高（96.7%和100.0%）；即使面对B组低毒力的表皮葡萄球菌，21 d时SLP的诊断效率也可保持在90.0%；总体诊断效率很好（95.6%）。.
结论: SLP比色法诊断PJI具有较高的敏感性、特异性以及诊断效率，是一种极具潜能的PJI诊断方法。.
Keywords: Silkworm larvae plasma colorimetry; periprosthetic joint infection; precise diagnosis.