Clinical utility of a dipstick assay in patients with brucellosis: correlation with the period of evolution of the disease

To examine the clinical utility of a dipstick assay for the detection of Brucella -specific IgM antibodies, and the correlation with the evolution of the disease. Twenty-six patients who were admitted to the General Hospital of Albacete (Spain) over a 2-year period and diagnosed with brucellosis were included in the study. One hundred and twenty-five serum samples collected at the time of diagnosis and at intervals during and after treatment were tested by the Coombs test, the standard seroagglutination test (SAT), the SAT in the presence of dithiothreitol (DTT-SAT), and a dipstick assay for the detection of Brucella -specific immunoglobulin M (IgM) antibodies. The sensitivity of the dipstick assay at the moment of the diagnosis was similar to that of the SAT (62% and 73%, respectively), somewhat higher than that of the DTT-SAT (50%), and lower than that of the Coombs test (100%). Patients with a negative dipstick test at the moment of diagnosis displayed a period of evolution of the disease longer than that of the dipstick-positive patients. After the beginning of therapy, the detection rate of the dipstick assay decreased faster than those of the SAT, the DTT-SAT, and the Coombs test. Thirty days after the start of therapy, the detection rate of the dipstick assay had decreased to 7%, whereas that of the SAT and DTT-SAT was 46%, and that of the Coombs test was still 92%. The dipstick assay could be used as a rapid diagnostic test for patients in the early stages of illness. Patients with a long period of illness will probably have a negative dipstick test, and could be diagnosed with the aid of the Coombs test and classical clinical findings.