Purple City Labs
Robust Testing for
Developed in our Lab,
proven in our Nursery
Why switch from PCR testing to HLVd OnSight?
Having in-house testing allows you to integrate testing in your routine nursery practices — on your own schedule, with immediate results and the ability to perform repeat tests for confirmation. PCR-based tests that entail samples sent to outside labs require longer turnaround times and are more costly, creating a barrier for quick and effective mitigation of Hop Latent Viroid. Additionally, RNA, which makes up HLVd, is a fickle molecule that rapidly degrades unless preserved well during transport. Reducing the time between sampling and testing minimizes this risk.
How accurate is HLVd OnSight?
HLVd OnSight is as accurate as many PCR-based tests on the market. The reaction is able to detect approximately 375 copies of the viroid per microliter. Even if it is possible to design molecular reactions with higher levels of sensitivity, the OnSight system as a whole is the most effective at population level screening as OnSight. See below for some comparison studies with other labs.
How long will it take to clear my facility of HLVd?
Depending on the level of infection, six to nine months is often sufficient for most operations. Purple City Genetics brought down HLVd levels to 0-1% (depending on cultivar) after using OnSight intensively for 6 months.
Do I need lab experience to run the HLVd OnSight test?
No experience is needed! Our step-by-step SOP and instructional videos are easy to follow and our lab team can offer additional support on how to effectively run the tests.
Do I need equipment for OnSight? Why is lab equipment sold separately?
You will need some basic lab equipment to run OnSight. This is not expensive and costs around $1,000. We have sourced and validated the equipment from different vendors and can direct you to them. We also offer loaner equipment if you would like to give OnSight a try before buying your own.
Why are you selling a proprietary test developed for your nursery?
Purple City has been a deep partner to experienced cultivators across the marketplace since 2008. We're selling HLVd OnSight after experiencing how effective the test is within our nursery. We recognize HLVd is a collective problem for everyone who cultivates cannabis, and are excited to share our solution with the cannabis community.
What tissue types can I test?
You can test all tissue types including leaves, stem, petiole and roots, depending on the particular application of OnSight in your facility. Our team will gladly help you identify a sampling plan for effective screening of your plants.
Comparison of Purple City Labs
OnSight for HLVd (LAMP method) with
other testing Labs (PCR method)*
OnSight V1May ‘21
We trained a San Francisco nursery to run a beta version of OnSight on stem tissue. They also collected leaf samples from the same plant being tested and sent them to a PCR-based testing lab.
Total Plants tested: 80
OnSight Positives: 29
Lab Positives: 10
All 10 positives detected by the lab were also detected by OnSight.
The 19 plants with a discrepancy between the two testing methods were re-analyzed by PCL and 16 were confirmed to be positive, while 3 were actually negative. OnSight v1 was more sensitive than the PCR-based lab but had a slight false negative rate.
OnSight V2November ‘21
A nursery in Oregon wanted to compare OnSight to two labs using PCR. They sampled 28 plants and sent them to PCL and the two other labs.
Total Plants tested: 28
OnSight Positives: 9
PCR Lab 1 Positives: 9
PCR Lab 2 Positives: 19
The 9 positive plants detected with OnSight were also detected by the two labs. We were not able to run secondary analysis on the conflicting samples.
OnSight V2April ‘22
A lab in Canada wanted to update their ISO accreditation to include using OnSight for HLVd detection. In order to do this they needed to conduct a blind proficiency test with 15 positive and 15 negative plant samples.
The lab using OnSight successfully diagnosed all 30 samples accurately.
OnSight V3October ‘22
After substantial improvements to the sensitivity and specificity of OnSight, the same nursery in Oregon wanted to run another trial comparing OnSight and PCR to each other by sending split samples to Purple City Labs and three labs.
Total Plants tested: 14
OnSight Positives: 2
PCR Lab 1 Positives: 2
PCR Lab 2 Positives: 2
PCR Lab 3 Positives: 0
The two positive samples were the same for OnSight and the two PCR labs.