Actinobacteriota, formerly known as Actinobacteria, is a significant phylum within the gut microbiota that plays a crucial role in human health. On an adult gut health test, Actinobacteriota serves as a marker for assessing various aspects of gut function, including digestion, immune regulation, and the production of beneficial metabolites. This phylum is well known for containing bacterial genera such as Bifidobacterium, which are associated with positive health outcomes, including the production of short-chain fatty acids (SCFAs), modulation of inflammation, and inhibition of harmful pathogens.

One of the primary functions of Actinobacteriota in the gut is its involvement in carbohydrate metabolism. Many species within this group are adept at breaking down complex carbohydrates and fibers, which are not digestible by human enzymes, into SCFAs like acetate and butyrate. These metabolites serve as an energy source for colon cells, help maintain the integrity of the gut lining, and contribute to a balanced inflammatory response. Therefore, a healthy level of Actinobacteriota on a gut health test is often seen as indicative of a diet rich in fiber and prebiotics, which supports overall gut health.

However, an imbalance in Actinobacteriota levels can be a marker of gut dysbiosis, a condition where the microbial community in the gut is disturbed. Low levels of beneficial bacteria like Bifidobacterium may indicate poor digestion of fiber, reduced SCFA production, and a higher risk of inflammatory conditions such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD). Conversely, an overgrowth of certain Actinobacteriota species, particularly pathogenic strains, could be associated with conditions like small intestinal bacterial overgrowth (SIBO) or contribute to metabolic disorders.

Actinomycetales are considered low abundance colonizers of the gastrointestinal tract with primary residence on the skin.

The Activated CD21low CD38- % biomarker measures the proportion of B cells with low CD21 expression and absent CD38 expression, representing a subset of atypical or activated B cells linked to immune dysregulation. These cells are associated with chronic immune activation (e.g., in HIV or hepatitis), autoimmune diseases (e.g., lupus, rheumatoid arthritis), and primary immunodeficiencies (e.g., CVID). They are often indicative of B cell exhaustion caused by prolonged antigen exposure. Elevated levels may signal chronic activation or autoimmune pathology, while interpretation requires clinical context, additional immune markers, and other laboratory findings to assess immune status effectively.

Activated CD21low CD38- B cells are a distinct subset of B lymphocytes associated with chronic immune activation and immune dysregulation. These cells exhibit low CD21 expression, absence of CD38, elevated activation markers like CD80 and CD86, and increased inhibitory receptors such as PD-1 and FCRL4. They produce class-switched antibodies, predominantly IgG and IgA, which often include autoreactive antibodies and those targeting persistent antigens. These cells play a role in chronic inflammation, autoantibody production, and disrupted immune tolerance, commonly linked to autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis, as well as chronic infections like HIV and hepatitis C. Reduced responsiveness to signaling pathways and cytokine secretion, including IL-6 and TNF-α, highlight their contribution to immune dysfunction. Monitoring these cells and their antibodies provides insights into chronic immune activation, autoimmune processes, and the efficacy of immunomodulatory therapies, making them valuable markers in diagnostics and disease management.

The Activated partial thromboplastin time (aPTT) test tells you how many seconds (s) it takes your blood to form a clot after body tissue(s) or blood vessel walls were injured.

Screening test for the factor V Leiden gene mutation and other causes of activated protein C resistance

Activated Vitamin B12, also known as holotranscobalamin (holo-TC), is a significant biomarker for Vitamin B12 status in the body. Unlike total B12, which measures both active and inactive forms, holo-TC specifically indicates the amount of Vitamin B12 that is available for cellular uptake and use. This makes it a more precise marker for assessing B12 deficiency, especially in clinical situations where accurate diagnosis is crucial.

Activated Vitamin B12, also known as holotranscobalamin (holo-TC), is a significant biomarker for Vitamin B12 status in the body. Unlike total B12, which measures both active and inactive forms, holo-TC specifically indicates the amount of Vitamin B12 that is available for cellular uptake and use. This makes it a more precise marker for assessing B12 deficiency, especially in clinical situations where accurate diagnosis is crucial.

In a semen analysis, "active sperm" typically refers to sperm motility. Active sperm are those that are capable of moving, and sperm motility is an important parameter in assessing male fertility.

Actomyosin is a smooth muscle protein found throughout the body. In the intestinal barrier's epithelial cells, actomyosin proteins form cables called the Actin Network.

Gastrointestinal microfilaments of the Actomyosin Network are critical for apical junctional complex biogenesis and function. The apical junctional complex, made up in part by tight junction proteins zonulin and occludin, is responsible for preventing antigen invasion and preservation of the biochemical homeostasis within the gastrointestinal tract. The Actomyosin Network can signal tight junction contractions and give structure to their assembly.

Acylcarnitine is a crucial molecule in the body, playing a significant role in the metabolism of fatty acids. Essentially, it acts as a transporter that helps move fatty acids into the mitochondria, the energy powerhouses of our cells, where they can be broken down and used for energy production. The process begins when fatty acids bind to carnitine, forming acylcarnitine, which can then cross the mitochondrial membrane. Once inside the mitochondria, the fatty acids are released from carnitine and undergo a process called beta-oxidation, which ultimately generates ATP, the energy currency of cells. Measuring levels of acylcarnitines in the blood can provide valuable insights into metabolic health. Abnormal levels may indicate metabolic disorders such as fatty acid oxidation defects, which can lead to energy production issues and accumulation of toxic substances in the body. Therefore, understanding and monitoring acylcarnitine levels is important for diagnosing and managing various metabolic conditions.

The ADAMTS13 activity and inhibitor assays are useful for the diagnosis of congenital or acquired form of TTP.

ADAMTS13 is a plasma protein responsible for regulating the interaction of platelets with von Willebrand factor (VWF) and physiologic proteolytic cleavage of ultra large (UL) VWF multimers at the Tyr(1605)- Met(1606) bond in the A2 domain of VWF. Reduced or absent ADAMTS13 activity can retain UL VWF that can trigger intravascular platelet aggregation and microthrombi causing clinical symptoms or signs of thrombotic thrombocytopenic purpura (TTP).

Measurement of ADAMTS13 activity and its inhibitor is crucial in the diagnosis of TTP, potentially fatal thrombotic microangiopathy (TMA) syndrome and further differentiation of congenital (Upshaw-Schulman syndrome) versus acquired (e.g. autoimmune-related disorder) etiology.

Adenosine Deaminase (ADA) is an enzyme that plays a vital role in the breakdown of adenosine, a building block of DNA and RNA. This enzyme is essential for the proper development and function of the immune system, especially for T lymphocytes (T cells), which are white blood cells that help the body fight infections and diseases. Without sufficient ADA activity, toxic byproducts can accumulate and disrupt immune function.

Adenovirus serotypes 40 and 41 cause acute gastroenteritis (inflammation of the stomach and intestines) primarily in children.