Metrics in Agile

Since all are turning to agile, definitely software tester have to equate their traditional methods into agile.

In non-agile there are some metrics used in testing

For e.g.,

To find the efficiency of test cases, we can say

[No.of.test cases those can be mapped into defects] / [Total no.of test cases]

is one of the ratios used in traditional software testing.

How to do this in agile process, where test case itself is not important (at least , test case documentation)

Likewise, there are many ratios/metrics which were non-agile period may not be directly applicable in agile era.. looking for the conversion or in simple terms,

"What are the ratios and metrics those can be useful in agile testing?"