I have severe Long COVID /ME and after being told by multiple people that Tlab was the gold standard tickborne test, I went for it and recently got a positive Borrelia FISH result back.
I spent the past week trying to work out how much to trust it, and the more I dig, the less I do. Here's why:
Tlab reports don't actually show the pathogen on the image
The two "representative images" on my report show red blood cells and green dots. Borellia is 3-4x times the width of a cell, and wide enough where it should light up. I've reviewed reports from other patients and they are the same.
My LabCorp results were negative
I'd had LabCorp's modified two-tier test (VlsE/pepC10), and it was negative. Standard testing is bad at catching early Lyme, but in late Lyme (arthritis, neurological, cardiac) modified two-tier testing catches 96-100% of cases in multicenter studies. Source VlsE also covers the main European species, which matters because I spent a lot of time hiking in Germany.
My math doesn't work out
With 1,000 people like me, using numbers that are deliberately generous to TLab:
- 30 have an active infection; 970 don't.
- LabCorp catches 90% of late infections, so only 3 infected people test negative, alongside about 960 uninfected people.
- Assume TLab catches half of real infections and wrongly flags 1 in 10 healthy people. That gives about 1.5 true positives and 96 false positives among the LabCorp negatives.
- So about a 1.5% chance my positive is real.
Even with much more pessimistic assumptions (higher exposure, LabCorp missing half of late infections, or TLab flagging only 3 in 100 healthy people), I still get roughly an 80-95% chance it's a false positive. For it to be a coin flip, I'd have needed to be about 65% sure I had an active infection before testing.
There's no published evidence of how often Tlab is positive in healthy controls
A diagnostic test's value depends on its false-positive rate, which you can only measure by testing healthy, unexposed people blind. There is no published study doing that for TLab's blood FISH, and the company does not share sensitivity and specificity numbers (confirmed via phone rep).
No one can actually back up why it's considered the best test
Every time I asked why TLab is the best, the answers were the lab director's background, the expensive confocal microscope, the fact that it's "molecular," and clinicians saying they trust it. None of that equals a false-positive rate. A better microscope makes faint signals easier to see, but that includes nonspecific probe binding, debris and autofluorescence, so it doesn't make a test more specific. The call is still a lab worker judging "signal above background."
Similar tests have failed when checked
- A modified microscopy method for spotting Borrelia and Babesia in blood was tested blind in Norway. It flagged structures it called Borrelia or Babesia in 85% of healthy controls with no tick-bite history, and PCR couldn't confirm them. Source
- A commercial phage-based Borrelia PCR gave a positive signal in 21 of 23 healthy controls. Its developers suggested healthy people might carry Borrelia; independent reviewers concluded the test lacked specificity. Source
The "it hides in tissue" argument doesn't make sense for positives
Late Lyme is rarely found in circulating blood, which is why blood PCR for Lyme has poor sensitivity. If the organism mostly lives in tissue, a blood test should rarely find it even in infected people. A test that rarely finds real infections needs near-perfect specificity for a positive to mean anything, and that's exactly the number that's missing. The tissue argument explains why a TLab negative wouldn't mean much. It doesn't explain why a positive should be trusted.
To defuse some objections:
- "Antibody tests are insensitive." True early on, before antibodies develop. But not true in late disease, which is what most of us are dealing with.
- "Healthy people can carry Lyme too." Asymptomatic infection exists, but those people still make antibodies; that's how we know about it. If every positive in a healthy person gets explained as hidden infection, no result could ever count against the test, and a test that can't fail can't be validated.
At the end of the day, Tlab seems to be revered because it provides the highest positive rate in a diagnosis-seeking population, not because of any published lab values or scientific rationale.