Yes. Create your req. structure. Create the test case structure and the test cases Map the testcases to the apr. req. Run and report bugs from your test cases in the test lab module. The database structure in TD is mapping testcase to defects, only if you have created the bug from the apr. test case. Maybe you can update the mapping by using some code in the bug script module (from the customize project funktion), as fare as I know, its not possible to map defects directly to an req.