Coxsackie A Antibodies, Serum - Panel currently includes testing against A-2, 4, 7, 9, 10, and 16 antigens. Although there is cross-reactivity among the enteroviruses by CF, most healthy people do not have titers >1:8. Therefore, detectable titers, especially those >1:32, should be considered diagnostic. Confirmed serodiagnosis is made by demonstration of a four-fold change in titers between acute and convalescent sera.