TSH receptor antibody LATS (Long Acting Thyroid Stimulator) is a blood test used to diagnose Graves disease, an autoimmune disorder that affects the thyroid gland. The test measures the level of antibodies that stimulate the thyroid gland to produce more hormones than necessary. The test is performed by taking a blood sample from the patient and processing it in a laboratory. Results are reported as a numerical value, with higher values indicating a greater likelihood of Graves disease.