FIG. 1.

Sequential assessment of viability and yield results from (A) laboratories that performed adequately throughout the QAP and (B) laboratories that either improved during the course of the QAP or failed to improve. Viabilities (upper panels) and yields (lower panels) of PBMC from HIV-positive (left panels) and HIV-negative (right panels) common donors supplied from each participating laboratory (same symbols in each panel) are shown. Dashed lines represent the required performance standards.