Ultrasensitive Detection of Clostridium difficile Toxins Reveals Suboptimal Accuracy by Toxin-Gene Cycle-Thresholds for Toxin Predictions.

The use of nucleic acid amplification tests (NAATs) for the diagnosis of Clostridium (Clostridioides) difficile infection (CDI) leads to overdiagnosis. To improve the clinical specificity of NAATs, there has been a recent interest in using toxin-gene cycle-thresholds (CT) to predict the presence and absence of toxins. Although there is an association between CT values and fecal-toxin concentrations, the predictive accuracy of the former is suboptimal for use in clinical practice. Ultrasensitive toxin immunoassays to quantify free toxins in stool offer a novel option for high-sensitivity fecal-toxin detection, rather than using surrogate markers for prediction.