Validação laboratorial de um método automatizado de dosagem da atividade de adenosina desaminase em líquido pleural e em líquido cefalorraquidiano

Abstract

Objective: The incidence of tuberculosis worldwide has emphasized the need for better assays designed to diagnose the disease, principally the extrapulmonary form. The objective of the present study was to validate the performance of an automated method for the determination of adenosine deaminase (ADA) activity in pleural fluid (PF) and cerebrospinal fluid (CSF), comparing it with a conventional method (the modified Giusti method). Methods: In total, 134 samples were selected from among those tested in our laboratory: 94 PF samples and 40 CSF samples. The ADA activity was determined using the two methods. Inter-and intra-assay precision was determined, linear regression analysis was performed, simple concordance tests were conducted, and the means of the differences were calculated. Results: The correlation coefficients for PF and CSF samples were, respectively, 0.96 and 0.95. Inter-assay precision was determined using 21 replicates at 3 different activity levels: low, medium and high. The percentage coefficient of variation (%CV) was, respectively, 5.9, 8.1 and 5.8 for PF samples, compared with 21.9, 18.6 and 13.8 for CSF samples. Intra-assay precision in %CV was 1.3 and 11.7, respectively, for PF and CSF samples. The concordance between the methods in PF and CRF samples was, respectively, 96.8% and 100%, considering the reference values for the diagnosis of TB to be 40 U/L (conventional) and 30 U/L (automated) in PF samples, versus 9 U/L (for both methods) in CSF samples. Conclusions: The results validate the use of the automated method of determining ADA activity in PF and CSF samples as an alternative to the conventional method. Keywords: Adenosine deaminase; Tuberculosis/diagnosis; Pleural effusion; Cerebrospinal fluid. ResumoObjetivo: A incidência global de tuberculose reforça a necessidade de melhores ensaios para o diagnóstico desta doença, principalmente da tuberculose extrapulmonar. O objetivo do trabalho foi validar o desempenho de um método automatizado para a determinação da atividade de adenosina desaminase (ADA) no líquido pleural (LP) e no líquido cefalorraquidiano (LCR), comparando-o com um método convencional (Giusti modificado). Métodos: Selecionaram-se 134 amostras da rotina laboratorial: 94 de LP e 40 de LCR. Foram realizadas as determinações da atividade de ADA através dos dois métodos. Calculou-se a precisão inter-e intra-ensaios, análise de regressão linear, testes de concordância simples e médias das diferenças. Resultados: Os coeficientes de correlação para as amostras de LP e LCR foram, respectivamente, 0,96 e 0,95. A precisão interensaio foi determinada pela média de 21 amostras replicadas em ensaios diferentes para 3 níveis de atividade: baixa, média e alta. Os coeficientes de variação em porcentagem (%CV) foram, respectivamente, 5,9, 8,1 e 5,8 para amostras de LP; e 21,9, 18,6 e 13,8 para amostras de LCR, respectivamente. A precisão intra-ensaio em %CV foi, respectivamente, 1,3 e 11,7% para amostras de LP e LCR. A concordância entre os dois métodos em amostras de LP e LCR f...

Diffuse Hypertrophic Pachymeningeal Tuberculosis

“…This report also demonstrates the clinical utility of CSF-ADA as a one of diagnostic tests in the diagnosis of central nervous system tuberculosis [ 5 ].…”

Intramedullary Tuberculoma of the Conus Medularis in an Immunocompetent Young Adult with no Pulmonary Tuberculosis, the Challenges of Diagnosis and Management

“…[ 2 4 10 13 14 28 ] Several other diagnostic adjunct have been used to diagnose tuberculous infection of the CNS; acid fast bacillus staining and cerebro spinal fluid culture, deoxyribonucleic acid genomic amplification using the polymerase chain reaction, high levels of cerebro spinal fluid adenosine deaminase, the presence of extraneural tuberculosis foci elsewhere in the body, and responsiveness to antituberculous therapy. [ 2 29 30 31 ] But none of these investigations are specific enough for establishing or confirming the diagnosis of spinal tuberculosis, non the less, a conus medullaris IMT.…”

Intramedullary Conus Medullaris Tuberculoma: A Case Report and Review of the Literature

“…A diagnosis of tuberculous infection of the CNS can be based on AFB staining and CSF culture, subacute to chronic lymphocytic CSF with high protein and low glucose levels, histopathological findings, DNA genomic amplification using the polymerase chain reaction (PCR) method, high levels of CSF-ADA, the presence of extraneural tuberculosis foci elsewhere in the body, and responsiveness to antituberculous therapy [4,24,25]. In our case, the initial diagnosis was based on extremely high levels of ADA in the patient's CSF.…”

“…After the operation, the patient suffered from urinary retention, which did not resolve. Tuberculoma of the conus medullaris was suspected due to the patient having very high CSF-ADA levels [4]. Since Thailand is an endemic area of tuberculosis, we do not routinely use tuberculin skin test or QuantiFERON-TB Gold test for diagnosis of active tuberculous infection.…”