Can my older cats (3 to 13 years old) catch feline lukemia from my kittens if they are current on their shots?

Vet tested my kittens for feline lukemia (they are 3 months old). I guess the test take about 9 minutes. The vet came in and said things looked good. Then about 12 minutes after the test he told me that there could be a chance they have it but he thinks there might have been a mess up on the test. Was told to keep kittens from other my other cats but they were already exposed to the kittens the day I adopted them from the animal shelter. I am just so worried about all of them.