The NK Vue diagnostic test for natural killer cell activity uses the principle of stimulation of whole blood with a proprietary cytokine followed by the quantitative detection of interferon-gamma using an immunoassay. NK Vue is intended to be used for the monitoring of the immune status of individuals. Measurement of NK cell activity could be a useful tool for assessing changes in immunosurveillance in patients with conditions or diseases where NK cell activity has been shown to be affected.