A single-tube radioimmunoassay for the antiviral agent 2,6-diamino-9-(2-hydroxyethoxymethyl)purine (A134U).

A direct radioimmunoassay for the detection of A134U in biological fluids and extracts has been developed. The entire assay, including scintillation counting, is performed using 12 X 55-mm centrifuge tubes and results in a sensitive, reliable, and relatively inexpensive procedure. The log-logit transformation is linear over a range of 1 to 30 pmol per sample. Intra-assay precision was found to be excellent with a coefficient of variation ranging from 4.1 to 14.5% for the standard curve with plasma and a coefficient of variation ranging from 4.0 to 17.8% for the standard curve with urine. Interassay precision and accuracy were also found to be good. With the antisera chosen for use, no cross-reactivity was found with acyclovir or its two known metabolites, while some cross-reactivity was seen with the corresponding two derivatives of A134U. Only very minor cross-reactivities were seen with a small number of other compounds out of a large number tested.