The new on-the-spot device, which can detect and distinguish between four different pathogens with high accuracy, is heading to implementation trials.
Syphilis, herpes, chlamydia and gonorrhoea may soon be diagnosable within the hour.
A new CRISPR-based tool detects the DNA and RNA of the four sexually transmitted infections, diagnosing without the need for laboratory infrastructure.
Importantly, it also detects an antimicrobial resistance marker – a critical inclusion given the recent spike in antibiotic-resistant gonorrhoea.
The portable point-of-care device is a world-first, developed by researchers at the Peter Doherty Institute for Infection and Immunity. It allows for diagnosis and treatment in the same visit and would be particularly valuable to regional, remote and underserved communities, the researchers said.
A study of the device, published this week in The Lancet Microbe, found high specificity (96–100%), good sensitivity for high bacterial/viral loads and high overall diagnostic accuracy (AUC 0.85–0.99) for most assays.
The rapid, multi-pathogen testing device is heading into implementation trials.
“This new device has been validated using 900 clinical samples, the largest set of STI samples reported globally for a CRISPR-based point-of-care device,” said Mr Matthew O’Neill, research support officer at the Doherty Institute and co-first author of the paper.
“When benchmarked against gold-standard laboratory PCR, the rapid test showed 97% –100% accuracy in correctly identifying negative results, a level of precision important for safe, evidence-based treatment decisions,” he told media.
However, the accuracy of the test relied heavily on pathogen load. When the cycle threshold (Ct) value was 35 or lower – indicating a higher organism load – sensitivity was typically 93%–98%. When Ct values were above 35, sensitivity dropped substantially for some assays.
For syphilis (T. pallidum), specificity was 98% and the AUC was 0.90. Overall sensitivity was 82.5%, increasing to 98% in samples with high bacterial load and decreasing to 67.9% in samples with low bacterial load. Most of the false negatives occurred in low-load samples, although repeat testing was able to detect many of these.
For herpes simplex virus (HSV), specificity was 98% and the AUC was 0.99, with excellent overall sensitivity (94.4%). As with syphilis, performance declined in samples with low viral load.
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Among HSV-positive samples, the reflex HSV-1/HSV-2 typing assay demonstrated 100% specificity and AUC values of 0.97-0.99 for HSV-1 and HSV-2. Sensitivity was 97% for HSV-1 and 96% for HSV-2, with missed detections occurring primarily in low viral load samples.
For gonorrhoea (N. gonorrhoeae), test performance was highly dependent on pathogen load. Specificity was 96.9%, AUC was 0.90 and overall sensitivity was 80%. Sensitivity was 93.1% in high-load samples but fell to 18.9% in low-load samples.
Detection of the resistance-associated gyrA mutation in gonorrhoea (cNG–gyrA assay) showed only moderate diagnostic accuracy, with specificity of 83.7%, AUC of 0.72 and overall sensitivity of 63.1%. Sensitivity was 71.7% in high-load samples but dropped to 13.6% in low-load samples.
For chlamydia (C. trachomatis), performance was similarly Ct-dependent. Overall sensitivity was 73%, rising to 95.3% in high-load samples and decreasing to 28.3% in low-load samples. Specificity was 98.2% and AUC was 0.85.
The researchers are now moving the device into implementation trials, with routine clinical use envisioned in the next five years.
