You may undergo the following tests to diagnose cryptosporidium infection:
- Acid-staining test. The simplest way to diagnose cryptosporidium infection is a method called an acid-staining test, which identifies cryptosporidium under a microscope. To obtain cells for the analysis, your doctor might ask for a stool sample, or in more extreme cases, take a tissue sample (biopsy) from your intestine for the test.
- Stool culture. Your doctor might also order a standard stool culture. Although this test cannot detect the presence of cryptosporidium, it may help rule out other bacterial pathogens.
- Other tests. Once it's clear that your infection is caused by cryptosporidium parasites, you may need further testing to check for development of serious complications. For example, checking liver and gallbladder function may determine whether the infection has spread. If you have both AIDS and cryptosporidiosis, a T-cell count — which measures the level of a certain white blood cell that's part of your immune system — can help predict the duration of the cryptosporidiosis. A T-cell count under 100 cells per microliter means you're more likely to have complications.