Figure 1: Bayesian nomogram for probability of metastatic disease as a function of pretest probability and negative SLN biopsy. The “pre” or pretest probability of axillary disease can be estimated using a risk calculator such as the one described [14]. The “sens” or sensitivity of SLN biopsy can be estimated using Table 1. Positions for the central dots are calculated assuming a SLN biopsy sensitivity of 80%, 85%, 90%, or 95%; specificity is assumed to be 100%. The calculation for the example patient is shown by the dotted line: if we assume sensitivity of 85% for SLN biopsy and a pretest probability of 62%, the posttest probability for axillary disease is 20% for this patient even in the presence of a negative SLN biopsy.