Portuguese EQA results for serogical diagnosis of syphilis and brucellosis

Abstract number: R2405

Faria A.P., Correia H., Matos R., Gomes M.A., Almeida S., Brito C., Mendes M., Melo P.

Objectives: Syphilis is a chronic infectious disease caused by spirochaete of the genus Treponema. It is usually transmitted by sexual contact or from mother to infant. Brucellosis is the most widespread zoonosis transmitted from direct contact from animals. As both diseases have a worldwide impact on human health it is necessary to monitor laboratory results. In 1989, the Portuguese EQA provider, Programa Nacional de Avaliação Externa da Qualidade (PNAEQ), created the Bacterial serology programme witch included toxoplasmosis, hydatidosis, rubella, syphilis, brucellosis and typhoid fever. Since 2002 the Bacterial Serology programme only includes syphilis and brucellosis.

The main objectives of this programme are evaluating participant's results and consequently improve clinical laboratory performance nationally. In this work we evaluate PNAEQ's participant results in syphilis and brucellosis.

Methods: Results of three annual assays, consisting of syphilis (human sera), a brucellosis sample (animal sera) and clinical information.

For syphilis diagnosis we evaluated the data for treponemal tests (FTA-abs, TPHA, TPPA, EIA IgG, EIA IgM, EIA IgG and IgM, Imunoblot) and non-treponemal tests (VDRL, RPR, USR). For brucellosis diagnosis we evaluated the data for Wright and rose Bengal tests. The results were statistically treated accordingly with the answers given by the laboratories.

Results: Throughout the year 2006 there was reduction of 20% in the number of answers sent to PNAEQ and in 2007 a more active participation.

For negative syphilis samples there is accuracy above 84% and for reactive samples the mean accuracy is 79%. In Brucellosis the percentage of correct answers for non-reactive samples is higher than 90% but for reactive samples the mean accuracy is 70%. The behaviour of different reagents used by laboratories was also studied, that being heterogeneous in the different assays and different bacterial load. The majority of the results were compatible with the clinical information provided.

Conclusion: There was a more active laboratory participation in 2007.

Treponemal tests for diagnosing syphilis had a better performance, as in rose Bengal test for brucellosis diagnose. A deeper study of reagent behaviour should be performed in order to improve the diagnosis of both syphilis and brucellosis.