If 'positive' (e.g., the suspect colony is S. aureus), the plasma will coagulate,[6] resulting in a clot (sometimes the clot is so pronounced, the liquid will completely solidify).
If 'negative', the plasma remains a liquid. The negative result may be S. epidermidis but only a more detailed identification test can confirm this, using biochemical tests as in analytical profile index tests methods. A false negative can be perceived if the sample is not allowed to cool for about 30 minutes at room temperature or 10 minutes in the freezer, given that the serum can melt. If truly negative, the serum will remain liquid after cooling.