Evaluation of SAT-Candida: a rapid RNA-based isothermal amplification assay for detection and identification of Candida spp. in vaginal specimens.

Background: This study evaluated the performance of the simultaneous amplification and testing (SAT) assay for detecting common Candida species in vaginal specimens compared with culture (gold standard) at the Obstetrics and Gynecology Hospital of Fudan University from December, 2024 to January, 2025.

Methods: Speimens were analyzed by both Candida culture (with MALDI-TOF MS identification) and the SAT-Candida assay. Discordant results were further confirmed by real-time polymerase chain reaction (RT-PCR) and bidirectional sequencing. A comparative analysis (kappa coefficient) was conducted as well. We assessed the limit of detection, technical specificity, repeatability and the clinical diagnostic effectiveness, including sensitivity, specificity, diagnostic accuracy, positive predictive value (PPV), and negative predictive value (NPV) of SAT-Candida assay.

Results: In our study, among the 472 initially collected specimens, 5 were excluded because the presence of the Candida species were outside the detection spectrum of the SAT-Candida assay. The ages of the rest 467 cases ranged from 13 to 77 years old, and by comparison with SAT-Candida assay and Candida culture, 444 concordant results and 23 discordant results were discovered. After the reconfirmation, the SAT-Candida assay presented a overall sensitivity of 98.7%, specificity of 97.8%, PPV of 97.9%, NPV of 98.7%, and diagnostic accuracy of 98.3% in detecting Candida species. The kappa value between Candida culture and SAT-Candida assay in detecting Candida species was 0.91.

Conclusions: This SAT-Candida assay is acute, highly sensitive, and specific, which can be applied as an optimal diagnostic tool for detecting and identifying common Candida species from vaginal samples of vulvovaginal candidiasis (VVC) suspected patients.