Reactive versus positive serology

I was trying to explain to a public health physician why I prefer reactive rather than positive for serology results.

The problem with assays used to detect antibodies to antigens from pathogens is that the antibodies detected can be cross reacting and just detecting them doesn’t always mean the patient has the infection. This is especially true for assays looking for IgM antibodies. This is why serologists tend to prefer reporting results as reactive or non-reactive rather than positive or negative. While the result may be positive, it doesn’t mean the patient positively has the disease in question.

It’s an important distinction and one I should never forget.