C-159. Performance of Trichomonas vaginalis Molecular Analyte-specific Reagent Testing on Primary Clinical Saline Suspensions

M. Napierala, J. Basile, T. Block, C. Miller, E. Munson;
Wheaton Franciscan Lab., Wauwatosa, WI.

Background: Specimen integrity has confounded direct examination of primary saline suspensions for Trichomonas vaginalis (Tv) to the point where a transcription-mediated amplification (TMA)-based Tv analyte-specific reagent (ASR; Gen-Probe, San Diego, CA) can supplant microscopy-based laboratory diagnosis. Detection of Tv from a primary saline suspension by this ASR may obviate the need for regional laboratories to supply numerous clients with ASR-specific specimen collection devices. Methods: 140 consecutive primary saline suspensions were cryptically-encoded for performance of Tv ASR following wet mount analysis. Aliquots of all suspensions were delivered to Gen-Probe transport tubes prior to ASR performance. Suspensions determined to be positive for Tv via microscopy were refrigerated, with aliquots delivered to Gen-Probe transport tubes at timed intervals. Discrepancies between Tv ASR-positive/wet mount-negative suspensions were tested with research use only (RUO) Tv alternative target TMA (Gen-Probe). Results: Fourteen wet mount-positive saline suspensions (10%) yielded a median luminescent value (x1000; RLU) of 5273 (range 4469-6066) after 200-μL aliquots were removed for Tv ASR. RLU ranged from 1 to 55 (median 2) in Tv ASR analysis of 110 saline suspensions that were wet mount-negative. Subsequent Tv ASR analysis of multiple Tv-positive saline suspensions revealed that Tv nucleic acid was detectable after more than one month of refrigeration; detectable from aliquots of a “rare” semi-quantitated specimen as small as 10 μL; and, detectable following only 25 minutes of incubation in a transport tube post-aliquot. Sixteen wet mount-negative saline suspensions (11.4%) were determined positive by Tv ASR; all specimens yielded a positive result when subjected to RUO Tv alternative target TMA. Specificity of RUO alternative target TMA was >96%. Conclusions: Tv molecular ASR adequately detects Tv from primary saline suspensions, providing a simple specimen alternative for a highly-sensitive laboratory diagnosis of trichomoniasis. Alternative target TMA is an appropriate means for confirmation of Tv ASR results.