Comparison of Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) and Agglutination Assays in Diagnosis of Brucellosis in Golestan Province, North of Iran

Brucellosis is one of the most common zoonotic infections worldwide. The clinical symptoms of brucellosis are similar to a wide range of diseases; hence, reliable diagnostic and laboratory methods are required to identify the causative agent. Iran is an endemic region of brucellosis, and many patients are misdiagnosed due to the nature of the infection. In this study, we aimed to evaluate and compare the use of the conventional Wright test and quantitative polymerase chain reaction (qPCR) for the diagnosis of brucellosis.

Diagnosis of brucellosis was performed using serological tests and PCR amplification of a gene encoding 31-kDa immunogenic Brucella abortus protein (BCSP31). Data were analyzed using the Chi-square test.

Brucellosis was diagnosed in 45 (69.23%) and 22 (38.8%) patients using the Wright test and qRT-PCR, respectively. The results of Wright and qRT-PCR assays were consistent in patients with negative results (90%). Moreover, qRT-PCR detected brucellosis in 25% of patients with Wright test titers <1/160, while 55.2% of the patients were positive with titers ≥1/160. No significant association was detected between positive PCR results and age, gender, and clinical symptoms.

qRT-PCR showed a reliable diagnostic method capable of detecting the infection in suspected individuals with negative Wright results or with Wright test titers <1/160. Also, the positive qRT-PCR assays were in agreement with the Wright test titer. Regarding the financial and availability issues as well as technical problems, the agglutination test remains the preferred method in Iran.