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limayesterday at 4:40 PM5 repliesview on HN

Unfortunately, there are major issues with this approach.

The vendor claims "lab-level accuracy" (conveniently omitting the actual accuracy numbers), but the test is a lateral flow test, which means its Limit of Detection is going to be orders of magnitude worse than molecular tests. Tick tests do not require FDA clearance, so their claims are most likely unreviewed.

Existing lab tests for ticks are almost universally based on PCR.

Ticks are small (especially nymphs) and extracting enough material can be tricky even for molecular testing, so I can't imagine an LFT test working terribly well, especially for nymphs, which are responsible for a lot of Lyme infections due to being easy to miss.

The other, bigger problem is that the test result is mostly useless.

The risk of Lyme transmission from an infected tick ranges rougly from <1% for a fresh bite (<24h) to ~10-25% once the tick is engorged (72h+). A positive tick test result would be insufficiently predictive of Lyme disease transmission on its own to justify taking antibiotics in most cases in the absence of other symptoms.

And you can't trust negative results either due to limited sensitivity, so you can't rule out transmission either.

In my opinion, tests like this can lead to worse overall health outcomes due to unnecessary treatment or withholding prophylaxis from someone who otherwise qualifies.


Replies

don_estebantoday at 7:27 AM

Yeah, I would be vary of accuracy of such tests.

The infected unfed ticks have few spirochetes in them. The numbers grow by two orders of magnitude as they feed - the reason why old bites are much more dangerous than the fresh bites.

lukanyesterday at 10:08 PM

"so I can't imagine an LFT test working terribly well, especially for nymphs, which are responsible for a lot of Lyme infections due to being easy to miss."

Even smaller and less noticeable are the larvae. And I know I learned that they cannot transmit the disease, because they only do so, if they have biten an infected animal before - so I never worried about small ticks, but apparently new research indicates, that this is wrong.

"However, newer research suggests that some pathogens, including Borrelia miyamotoi, may be transmitted from the adult female tick directly to her offspring.

This means larval ticks may already be infected before their first bite."

https://danielcameronmd.com/larval-ticks-borrelia-miyamotoi/

titotoday at 3:21 AM

It's been 15 years since I worked on open source PCR machines, but has someone not figured out how to build a "one time use" disposable type qPCR test? A single test, not an instrument. There's no way these types of tests should be left up to lateral flow etc.

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margalabargalayesterday at 5:35 PM

> The vendor claims "lab-level accuracy" (conveniently omitting the actual accuracy numbers)

Hey, labs have QC failures all the time.

layla5aliveyesterday at 5:15 PM

The standard isn't to avoid antibiotics until symptoms occur. The standard for a sufficiently attached deer tick in a high risk area is PEP:

Lyme post-exposure prophylaxis (PEP) is a single dose of doxycycline (200 mg for adults, or weight-adjusted for children) taken within 72 hours of removing a high-risk blacklegged tick bite to prevent Lyme disease.

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