Trich often has no symptoms, so a laboratory test is critical for accurate diagnosis. These tests are done on fluids from the vagina or urethra. A common test with females is a wet mount, where the sample is placed on a slide and examined under a microscope. Other tests include antigen detection tests, tests that detect the genetic material of the virus; and tests that involve growing a specimen in a culture dish for several days.
Trich is harder to detect in males, and the "wet mount" microscope approach doesn't work as well for men. Males are usually diagnosed with culture tests done with swabs from the urethra or urine/semen specimens. Nucleic acid hybridization tests
have excellent sensitivity in males.
If one partner has trich, both partners need to be treated, otherwise reinfection might occur. Remember, symptoms with trich are not common, so testing is the key.
Read more about trichomoniasis at http://www.ashastd.org/std-sti/trichomoniasis.html
Hope this helps.