Objective: The Becton Dickinson BDProbeTec ET System is a new semiautomated system using strand displacement amplification technology that simultaneously amplifies and detects Chlamydia trachomatis and Neisseria gonorrhoeae DNA. The strand displacement amplification products are hybridized with a fluorescent detector probe and are captured by a chemiluminescent assay in a microwell format. An amplification control is also included to monitor assay inhibition. This study evaluated the performance of the BDProbTec ET system in detecting C trachomatis and N gonorrhoeae in male and female urine specimens, calculated its ability to process large volumes of specimens, and determined the inhibition rate.
Materials and methods: Eight hundred twenty-five male and 399 female urine specimens were tested for both C trachomatis and N gonorrhoeae with the BDProbeTec ET system, and results were compared with those of the Roche Amplicor Cobas system. All urine specimens were processed on both assays on the same day they were received, according to the manufacturers' instructions. Discrepant results were resolved by in-house polymerase chain reaction assays. Internal or amplification controls were also used in each specimen assay to monitor inhibition. The throughput of the BDProbTec ET system was further tested with 150 urine specimens on an 8-hour shift for 2 days.
Results: The overall sensitivity, specificity, positive predicative value, and negative predicative value for for detection of chlamydia were 95.3%, 99.3%, 95.9%, and 99.2% for strand displacement amplification and 95.9%, 98.3%, 90.6%, and 99.3% for the Roche Amplicor system. For detection of gonorrhea, these values were 100%, 99.7%, 88.2%, and 100% and 96.7%, 98.9%, 69%, and 99.9%, respectively. The overall inhibition rates for both strand displacement amplification and Roche Amplicor were less than 3.5%. The BDProbTec ET system was able to produce 150 results each for chlamydia and gonorrhea and the internal control within the 8-hour shift.
Conclusions: The performance characteristics of the BDProbeTec ET assay are similar to those of the Roche Amplicor polymerase chain reaction for detection of chlamydia and gonorrhea in male and female urine specimens. The system was able to produce 300 results in an 8-hour shift.