Virtual Probe (VP), proposed for characterization of spatial variations and for test time reduction, can effectively reconstruct the spatial pattern of a test item for an entire wafer using measurement values from only a small fraction of dies on the wafer. However, VP calculates the spatial signature of each test item separately, one item at a time, resulting in very long runtime for complex chips which often require hundreds, or even thousands, of test items in production. In this paper, we propose a new method, named Joint Virtual Probe (JVP), which can jointly derive spatial patterns of multiple test items. By simultaneously handling a large group of test items, JVP significantly reduces the overall runtime. And the prediction accuracy can also be improved because of JVP's implicit use of inter-test-item correlations in predicting spatial patterns. The experimental results on two industrial products, with 277 and 985 parametric test items in the production test programs respectively, demonstrate that, JVP achieves an average speedup of ~ 170X and ~ 50X over VP in the pre-test analysis and the test application phases respectively, as well as a slightly higher prediction accuracy than VP.