HLA-B*27 / Antigen HLA-B*27 **

. Pepsinogens are inactive precursors of pepsin, proteolytic enzymes present in gastric juice, and are immunologically classified into pepsinogen I (PG I) and pepsinogen II (PG II).
. Pepsinogen I: Secreted by the chief cells and mucous neck cells in the fundus and corpus of the stomach. Low levels of Pepsinogen I may indicate atrophic gastritis, particularly in the corpus of the stomach.
. Pepsinogen II: Secreted by the cells throughout the stomach and proximal duodenum. Elevated levels may suggest gastric inflammation or more extensive gastric mucosal damage.
. Pepsinogen I/II Ratio: This ratio is a marker for atrophic gastritis. A low Pepsinogen I/II ratio (<3) may indicate atrophic gastritis or gastric mucosal atrophy. A high ratio is typically seen in normal gastric function. . This test is valuable in screening for precancerous gastric conditions, monitoring patients at risk of gastric cancer, and differentiating between types of gastritis.

The Dihydrotestosterone (DHT) test is performed to measure the level of Dihydrotestosterone (DHT) in the blood. DHT is a potent androgen hormone, metabolized from testosterone by the action of the enzyme 5-alpha reductase. DHT plays an important role in the development of male sexual characteristics and affects various physiological functions in the body.

An ADAMTS13 activity assay test measures the level of activity of the ADAMTS13 enzyme in a blood sample, which is crucial for regulating the size of von Willebrand factor (VWF) multimers and preventing excessive blood clotting; a low ADAMTS13 activity level is strongly associated with the diagnosis of thrombotic thrombocytopenic purpura (TTP). 

. C-peptide is a protein fragment released in equal amounts with insulin when proinsulin is cleaved.
. C-Peptide is useful in the evaluation of pancreatic beta cell function (e.g., helping distinguish type 1 from type 2 diabetes mellitus, or monitoring patients who have received islet cell or pancreatic transplants) and for determining the source of insulin in patients with hyperinsulinemic hypoglycemia (e.g., distinguishing insulin-secreting tumors from exogenous insulin administration).