ABSTRACT
BACKGROUND: Alpha-defensin has been widely studied for the diagnosis of periprosthetic joint infection (PJI). However, there is a lack of detailed information regarding the proper laboratory technique of the enzyme-linked immunosorbent assay (ELISA) method, such as sample dilution. AIM: To assess the influence of dilution in the synovial fluid during ELISA for the diagnosis of knee PJI; and determine which dilution presents a better performance. METHODS: Forty samples of synovial fluid from arthroplasty knees were included, 17 in the infected group and 23 in the aseptic group, according to Musculoskeletal Infection Society criteria. Initially, five synovial fluid samples from each group were assessed for quantitative analysis of alpha-defensin using ELISA. Different dilution ratios (1:10, 1:100, 1:500, 1:1000 and 1:5000) were tested based on the predetermined cutoff value of 5.2 mg/L. The dilutions that performed better were used to compare the results of all samples. RESULTS: For infected cases, a gradual increase in the dilution of synovial fluid samples led to an equivalent increase in alpha-defensin level. The same was not observed in the aseptic cases. Both 1:1000 and 1:5000 dilutions presented satisfactory results to differentiate infected and aseptic cases. Further analyses were performed using 1:1000 and 1:5000 for all 40 samples. The 1:1000 dilution resulted in a sensitivity of 88.2% (95%CI, 66%-98%) and specificity of 95.7% (95%CI, 79%-99%), whereas the 1:5000 dilution presented a sensitivity of 94.1% (95%CI, 73%-99%) and a specificity of 100% (95%CI, 86%-100%). CONCLUSION: The synovial fluid dilution had an important influence on the alpha-defensin ELISA results. Dilutions of 1:5000 showed the best performance for the diagnosis of knee PJI. The results of this study set the basis for a more reliable and reproducible alpha-defensin ELISA during the investigation of PJI, contributing to the expansion of this technique in different treatment centers worldwide.
ABSTRACT
BACKGROUND: The quantitative alpha-defensin enzyme-linked immunosorbent assay (ELISA) demands a prior synovial fluid centrifugation, whereas this processing is not routinely required prior to the alpha-defensin lateral flow test. AIM: To evaluate whether a prior synovial fluid centrifugation could lead the lateral flow performance to achieve comparable results to ELISA during periprosthetic joint infection (PJI) diagnosis. METHODS: Fifty-three cases were included in this study: 22 classified as PJI and 31 classified as aseptic cases, according to Musculoskeletal Infection Society 2013 criteria. Synovial fluid samples were submitted to centrifugation, and the supernatant was evaluated by ELISA and lateral flow tests. The sensitivity (SE), specificity (SP) and accuracy of each method were calculated as well as the agreement between those two methods. RESULTS: In all of the 31 samples from aseptic patients, alpha-defensin ELISA and lateral flow tests showed negative results for infection. Regarding the 22 infected patients, the lateral flow test was positive in 19 cases (86.4%) and the ELISA was positive in 21 (95.5%). Sensibility, SP and accuracy were, respectively, 86.4% (95%CI: 65.1%-97.1%), 100% (95%CI: 88.8%-100%) and 93.2% (95%CI: 82.8%-98.3%) for the lateral flow test and 95.5% (95%CI: 77.2%-99.9%), 100% (95%CI: 88.8%-100%) and 98.1% (95%CI: 89.9%-100%) for ELISA. An agreement of 96.2% between those methods were observed. No statistical difference was found between them (P = 0.48). CONCLUSION: Alpha-defensin lateral flow test showed high SE, SP and accuracy after a prior synovial fluid centrifugation, achieving comparable results to ELISA. Considering the lower complexity of the lateral flow and its equivalent performance obtained in this condition, a prior centrifugation might be added as a valuable step to enhance the PJI diagnosis.
ABSTRACT
Desde a primeira descrição por Percivall Pott da tuberculose de coluna vertebral, tem-se evoluído muito na abordagem dessa doença. Porém ainda existem muitas controvérsias em relação à prevenção das deformidades. Os objetivos de nosso estudo são avaliar as características clínicas e radiológicas de pacientes com tuberculose de coluna e comparar o tratamento conservador isolado com o cirúrgico associado a antibioticoterapia, principalmente quanto à deformidade residual e déficit neurológico. Nosso trabalho é retrospectivo com avaliação de prontuários e radiografias iniciais e ao final do seguimento. O quadro neurológico foi avaliado através da escala da ASIA e as deformidades foram medidas pelo método de Cobb. Foram avaliados 38 pacientes, 11 pacientes foram operados e 27 receberam somente antibioticoterapia. 15 pacientes tinham déficit neurológico, todos melhoraram independente do tipo de tratamento. A média de cifose torácica focal e regional no início do seguimento foi respectivamente 48,8° e 47,86°. Houve aumento da deformidade na região torácica, segmento mais acometido, de 6,3° focal e 9,8 regional ao final de 5 anos. O tipo de tratamento não influenciou na progressão da cifose. Paciente com menos de 15 anos e cifose maior que 30° tiveram pior prognóstico quanto à progressão da deformidade.
Much has evolved since Percivall Pott's first description of vertebral tuberculosis. However, there still is much controversy regarding the best approaches to prevent deformities. The objectives of this study were to evaluate the clinical and X-ray characteristics of patients with vertebral tuberculosis and to compare the conservative treatment alone to the surgical one associated with antibiotic therapy, particularly regarding residual deformity and neurological deficit. A retrospective evaluation of baseline and end-point X-ray studies and of the medical files was performed. The neurological status was evaluated by using the ASIA scale and the deformities were measured using the Cobb method. Thirty-eight patients were evaluated: 11 were surgically treated and 27 received only antibiotics. Fifteen patients presenting neurological deficit showed improvement regardless of the treatment method employed. The mean focal and regional thoracic kyphosis at baseline was 48.8° and 47.86°, respectively. An increased incidence of thoracic deformity was found, also being the most affected segment, from 6.3° focal and 9.8° regional after 5 years. The type of treatment has not interfered on kyphosis progression. Patients below the age of 15 and with kyphosis above 30° had worse prognosis regarding deformity progression.
