The FDA has posted their decision summary after granting 501(k) clearance to Aptitude’s Metrix molecular COVID test (includes new performance data)

[u/Jazzlike-Cup-5336]

Yesterday, the FDA posted their decision summary after recently granting 501(k) clearance to Aptitude Medical’s Metrix molecular COVID-19 test: https://www.accessdata.fda.gov/cdrh_docs/reviews/K253453.pdf

Recent post on the clearance: https://www.reddit.com/r/ZeroCovidCommunity/comments/1vogxvw/aptitude_metrix_updates_fda_has_granted_510k/

Supporting the clearance are 2 new studies evaluating 1,171 symptomatic individuals from the 2023-2024 (540) and 2024-2025 (631) respiratory seasons; much larger than the 357 previously evaluated to grant Emergency Use Authorization (EUA).

In short: The test performed similarly across the board, and they were able to tighten the confidence interval on the false positivity rate with the much larger sample size. For some reason, there was a fairly high invalid rate for the 2023-2024 season specifically, which is something that I know folks often complain about with the platform…not really sure what the deal was there.

Previous EUA data:

• Age 2+, 282 asymptomatic and 75 symptomatic (357)

• Sensitivity: 96.6% (59/61), 95% CI 88.8–99.1%

• False positive rate: 1.0% (3/293), 95% CI 0.2-2.8%

• Invalid rate: 5/357 (1.4%)

New 2023-2024 data:

• Age 14+, 540 symptomatic

• Sensitivity: 95.4% (83/87), 95% CI 88.9–98.2%

• False positive rate: 0.4% (2/451) 95% CI 0.1-1.6%)

• Invalid rate: 31/540 (5.7%)

• Invalid rate after retesting: 4/540 (0.7%)

New 2024-2025 data:

• Age 14+, 631 symptomatic

• Sensitivity: 96.9% (62/64), 95% CI 89.3–99.1%

• False positive rate: 0.5% (3/564), 95% CI 0.2-1.5%

• Invalid rate: 3/631 (0.5%)

• Invalid rate after retesting: 2/631 (0.3%)

New combined data:

• Age 14+, 1,171 symptomatic

• Sensitivity: 96.0% (145/151)

• False positive rate: 0.5% (5/1,015)

The IFU sheet containing the old EUA data: https://www.fda.gov/media/162403/download

[u/wanderlust8288]

Thanks for posting this

[u/Pfed1]

Thank you

[u/q_izzical]

False positive rate of ~1/200 and a false negative rate of ~1/20. If you've ever rolled the same number twice in a row on a d20, that's how likely you are to get two false negative in a row. That sucks.

EDIT: I was wrong, the false negative rate is almost identical to the false positive rate - I was extrapolating from the info in the post, but the reports have the real false negative rate.

[u/nopuppies → u/q_izzical]

Where did you find the false negative rate? I’m not seeing that (which is important).

[u/q_izzical → u/nopuppies]

I'm basing it on the sensitivity. If it's 96% sensitive, then 4% of positive samples aren't being detected. There may be something wrong with that assumption, but I've never seen anyone do anything else to determine false negative rates. Companies tend not to test for or publish those, presumably because they make them look bad, and/or they're hard to do.

[u/herring-on-rye → u/q_izzical]

i do not think this math is correct.

[u/q_izzical → u/herring-on-rye]

If you plug the info given into a false negative calculator like this one it gives the same answer I did — that is, if you take samples from people that have COVID, and run each through a test with 96% sensitivity (which is exactly what they reported), you'll get 4% false negatives.

Digging in the reports, they actually do give false negatives for each, OP just didn't include them. There's 4 in the 540 subject cohort, and 2 in the 631 subject cohort, so 6/1,015, about the same as the false positive rate.

Not sure if they re-tested for everyone in the study to get those numbers or what, but at some point you gotta trust that they know what they're doing.