Could you share what kind of tests these are? To the best of my knowledge, the only test we can do on our own without any specialised lab equipment is antibody tests, which doesn't necessarily reflect the health status of an individual. The gold standard for COVID-19 testing is RT-PCR, which is a genetic test that identifies the presence of the virus via genetic identification. This can't be done at home since it requires specific lab equipment.
Asymptomatic carriers are a concern, because there's no urgency for them to get tested since they don't know they've been infected. Presumably, these individuals contracted the disease but their immune systems have been able to fight it to a degree that symptoms never show. I'm not even sure if these carriers would even have a significant amount of circulating antibodies anyway for antibody-detection kits.