Laboratory-based diagnosis of brucellosis--a review of the literature. Part II: serological tests for brucellosis.
Brucellosis is a common zoonotic disease transmittable to humans from infected animal reservoirs. Malta, Rock, Gibraltar, Cyprus or Mediterranean fever, Bang's disease, intermittent typhoid or typho-malarial fever, undulant fever, etc. are just various synonyms for brucellosis. Patients suffering from this disease show unspecific symptoms, e.g. fever, chills, malaise, arthralgia, headache, tiredness and weakness. Human brucellosis may be caused by four of totally six genetically and phenotypically closely related Brucella species, i.e. B. melitensis, B. abortus, B. suis and B. canis. Although many organ systems may be involved, brucellosis is rarely fatal. Therapeutic failure and relapses, chronic courses and severe complications like bone and joint involvement, neurobrucellosis and endocarditis are characteristic for the disease. A definite diagnosis requires the isolation of Brucellae from blood, bone marrow or other tissues. However, cultural examinations are time-consuming, hazardous and not sensitive. Thus, clinicians often rely on the indirect proof of infection. The detection of high or rising titers of specific antibodies in the serum allows a tentative diagnosis. A variety of serological tests has been applied, but at least two serological tests have to be combined to avoid false negative results. Usually, the serum agglutination test is used for a first screening and complement fixation or Coombs' test will confirm its results. As Brucella ELISAs are more sensitive and specific than other serological tests, they may replace them step by step. This review will summarize advantages and disadvantages of the serological techniques used in clinical laboratories for indirect verification of human brucellosis.