I heard this tests might mistaken if you are negative.
I mean if you are possitive, it will show you possitive. But if you are negative it might Show you as Possitive or negative. This test aren't perfect but we also use our own test kits for the confirmation of the positive results... we test the possitive results again... our own test kits takes more time but the results are certain...
Thats why nations shouldn't rely on this chinese kits they also need a backup plan. Other than that this 15 minute kits speeding things up for some negatives, so it is fine.