The second step in diagnosis requires certain tests to confirm the diagnosis and rule out other possible diseases. The initial tests include blood and urine samples for uric acid. If these tests reveal high uric acid levels, then suspicion for Lesch-Nyhan disease goes up. Uric acid is considered a screening test for Lesch-Nyhan disease. Uric acid levels alone are not sufficient for definitive diagnosis. The reason is that there are some other diseases where uric acid levels are also high, and some children with Lesch-Nyhan disease do not have high uric acid levels.
Confirmatory tests include measurements of the HPRT gene and protein activity. A fresh sample of blood should be collected and sent to a genetics laboratory to examine the gene. This test provides a definitive diagnosis and allows the lab to devise a test that might be useful for other family members. A fresh sample of blood or a sample of a tiny spot of skin should be sent to a metabolism laboratory to examine the living cells. These tests are the best for predicting how severe the disease could become.