Analysis of 506 consecutive positive serologic tests for brucellosis in Saudi Arabia.

Brucellosis is common in the central region of Saudi Arabia. The major clue to the diagnosis is serologic testing. In 3 years, over 500 positive patients who had a titer of 1:160 or more were identified. Brucella species was the single organism most commonly recovered in all blood cultures, being found in 24% of patients with cultures positive for pathogenic bacteria. The expected greater number of Brucella cultures with high initial recorded titer was confirmed; 31% of the positive high-titer group had positive Brucella cultures. Conclusive correlation was uncommon below the 1:640 titer. The lower titers were less useful as indicators of active disease in this population, in which many people appear to have persistent low antibody levels.