crystal meth and blood test false positives?

[sickofthesystem]

SWIM said that they had just done a fairly good line of crystal and got arrested for being under the influence and forced to take a blood test. Of course they said the test came up positive for methamphedamine and amphedamine. SWIM asked me and I pass the question on to you, Is there any other drug that would cause a false positive with a blood test and what would it be? Your help is greatly appreciated.