Medical Database

KRAS Gene Mutation Analysis is a molecular diagnostic test used to identify activating variants in the KRAS gene, which encodes a GTPase involved in regulating cell proliferation, differentiation, and survival. KRAS mutations are frequently associated with colore**al, pancreatic, and non-small cell lung cancers and can contribute to uncontrolled tumor growth. Testing typically analyzes tumor tissue or other validated specimens using methods such as real-time PCR, allele-specific PCR, next-generation sequencing, or other molecular techniques. Detection of specific KRAS variants can provide clinically relevant information for tumor classification, prognosis, and therapeutic decision-making. In colore**al cancer, KRAS mutation status is particularly important because activating KRAS mutations are associated with lack of response to anti-EGFR therapies. Results should be interpreted alongside tumor histology, clinical findings, and other molecular biomarkers.

Leukotriene E4 (LTE4) is a stable urinary metabolite of cysteinyl leukotrienes, which are potent inflammatory mediators derived from arachidonic acid through the 5-lipoxygenase pathway. LTE4 is produced from leukotriene C4 and leukotriene D4 and is excreted in urine, making urinary LTE4 a useful noninvasive biomarker of cysteinyl leukotriene production. Measurement of urinary LTE4 may support evaluation of patients at risk for mast cell activation syndrome (eg, systemic mastocytosis, IgE-mediated allergies, or aspirin-exacerbated respiratory disease. Elevated levels can reflect increased leukotriene pathway activity and may correlate with disease severity or inflammatory responses in selected clinical settings. Testing can be useful when assessing suspected mastocytosis or monitoring leukotriene-mediated inflammation.

PAX2 immunohistochemistry is a tissue-based assay that detects expression of the paired box gene 2 (PAX2) protein in formalin-fixed, paraffin-embedded tissue specimens. PAX2 is a nuclear transcription factor involved in embryologic development of the kidney, Müllerian tract, and related structures. Immunohistochemical evaluation of PAX2 expression can support the identification and classification of tumors with Müllerian or renal origin. It is particularly useful in the differential diagnosis of gynecologic and renal neoplasms, including ovarian, endometrial, and renal tumors, when interpreted alongside morphology and other immunohistochemical markers. Nuclear staining is evaluated in tumor cells and compared with appropriate internal and external controls.

The HIV Co-Receptor Tropism (Trofile) Assay is a molecular test used to determine which cellular co-receptor, CCR5 or CXCR4, HIV-1 predominantly uses to enter host cells. This information can guide the use of CCR5 antagonist antiretroviral therapies, such as maraviroc, which are effective only against CCR5-tropic virus. The assay analyzes viral envelope sequences or functional viral entry to characterize HIV-1 tropism and may identify CCR5-tropic, CXCR4-tropic, or dual/mixed-tropic populations. Testing is generally performed using plasma from individuals with detectable HIV-1 RNA. Results can help clinicians evaluate whether a CCR5-targeting regimen is appropriate, particularly in treatment-experienced patients. Interpretation should consider viral load, treatment history, assay sensitivity, and current antiretroviral therapy guidelines.

Prostate Cancer Antigen 3 (PCA3) is prostate-specific, that is markedly overexpressed in prostate cancer cells compared with benign prostate tissue. PCA3 testing is typically performed on urine collected after a digital re**al examination, which releases prostate cells into the urinary tract. The assay measures PCA3 RNA and commonly reports a PCA3 score based on the ratio of PCA3 to prostate-specific antigen (PSA) RNA. Unlike serum PSA, PCA3 is less influenced by benign prostatic hyperplasia and prostatitis. PCA3 testing may help assess the likelihood of prostate cancer, particularly in men with an elevated or persistently abnormal PSA level and a previous negative biopsy. Results should be interpreted alongside clinical findings, PSA levels, imaging, and other risk factors.

Fibroblast Growth Factor 23 (FGF23) is a hormone primarily produced by bone cells, particularly osteocytes and osteoblasts, and plays a central role in regulating phosphate and vitamin D metabolism. FGF23 acts mainly on the kidneys to reduce phosphate reabsorption by decreasing sodium-phosphate cotransporter expression, thereby promoting urinary phosphate excretion. It also suppresses the production of 1,25-dihydroxyvitamin D (calcitriol), reducing intestinal phosphate absorption. FGF23 activity requires the co-receptor α-Klotho. Measurement of circulating FGF23 may assist in evaluating disorders of phosphate homeostasis, including hereditary hypophosphatemic disorders, tumor-induced osteomalacia, and chronic kidney disease.

G6PC (Glucose-6-phosphatase, Catalytic Subunit) gene mutation analysis is a molecular genetic test used to identify pathogenic variants associated with Glycogen Storage Disease Type 1a (GSD Ia), also known as von Gierke disease. GSD Ia is an autosomal recessive metabolic disorder caused by impaired glucose-6-phosphatase activity, resulting in defective conversion of glucose-6-phosphate to free glucose. Affected individuals may develop severe fasting hypoglycemia, hepatomegaly, lactic acidosis, hyperuricemia, and hyperlipidemia. Molecular testing typically evaluates the G6PC gene for sequence variants and may help confirm a clinical diagnosis, distinguish GSD Ia from other glycogen storage disorders, and support family or carrier testing.

Plasma phosphorylated tau 217 (p-tau217) is a blood-based biomarker associated with Alzheimer’s disease (AD) pathology. Tau hyperphosphorylation contributes to the formation of neurofibrillary tangles, a characteristic feature of AD. Elevated plasma p-tau217 levels are strongly associated with amyloid-β and tau pathology identified by cerebrospinal fluid (CSF) analysis and positron emission tomography (PET). Levels increase progressively in amyloid-positive individuals and correlate with advancing tau pathology, cognitive decline, and disease progression. Plasma p-tau217 may also help distinguish AD from other neurodegenerative disorders, including frontotemporal dementia, progressive supranuclear palsy, and Parkinson’s disease.

Chitotriosidase is a chitin-degrading enzyme produced predominantly by activated macrophages and is measured in serum as a biomarker of macrophage activation and lysosomal storage disorders. Serum chitotriosidase testing is particularly useful in the evaluation and monitoring of Gaucher disease, in which levels may correlate with disease burden and treatment response. Markedly elevated activity can also occur in other conditions associated with macrophage activation, including certain lysosomal storage disorders, infections, and inflammatory diseases. Testing may support diagnosis when interpreted alongside clinical findings, enzyme studies, and genetic analysis. Serial measurements can help assess response to enzyme replacement or substrate reduction therapy.

Chymotrypsin is a proteolytic digestive enzyme produced by the pancreas and released into the small intestine, where it helps break down dietary proteins. Because chymotrypsin remains relatively stable during intestinal transit, its concentration in stool can provide an indirect measure of pancreatic enzyme secretion. Reduced f***l chymotrypsin levels may indicate pancreatic exocrine insufficiency, which can occur in chronic pancreatitis, cystic fibrosis, pancreatic tumors, or after pancreatic surgery. The test may be useful in evaluating symptoms such as chronic diarrhea, steatorrhea, abdominal discomfort, weight loss, and malabsorption. Results should be interpreted alongside clinical findings and other pancreatic function tests, particularly f***l elastase.