Norepinephrine, also known as noradrenaline, is important for mental focus and emotional stability.

Norepinephrine functions as a neurotransmitter and hormone that regulates the “fight or flight” response and elevates blood pressure and heart rate, stimulates wakefulness, and reduces digestive activity.

Norepinephrine, also known as noradrenaline, is important for mental focus and emotional stability.

Norepinephrine functions as a neurotransmitter and hormone that regulates the “fight or flight” response and elevates blood pressure and heart rate, stimulates wakefulness, and reduces digestive activity.

The Norepinephrine / Epinephrine ratio is an indicator of epinephrine (adrenaline) conversion (epinephrine is synthesized from norepinephrine). Anxiety, burnout, and poor blood sugar control are associated with a relative epinephrine depletion, and thus an elevated Norepi:Epi ratio.

The Norepinephrine / Epinephrine ratio is an indicator of epinephrine (adrenaline) conversion (epinephrine is synthesized from norepinephrine). Anxiety, burnout, and poor blood sugar control are associated with a relative epinephrine depletion, and thus an elevated Norepi:Epi ratio.

Normetanephrine, a metabolite of norepinephrine, is at normally low levels in the plasma. Certain tumors increase the levels and will increase the levels of nor-metanephrine. The Normetanephrine test, when normal, means these tumors are not present.

Normetanephrine is a metabolite of norepinephrine (noradrenaline), one of the body's main stress hormones. It is measured in plasma or 24-hour urine primarily to help diagnose or exclude pheochromocytoma (an adrenal tumor) and paraganglioma (a related extra-adrenal tumor). Most healthy people have very low levels. A high result is common and does not automatically indicate a tumor — false positives from medications, stress, and improper sample collection are frequent. Levels below 4× the upper limit of normal usually need repeat testing before further workup; levels above 4× the upper limit are highly specific for tumor.

Metanephrine and normetanephrine are breakdown products (metabolites) of the catecholamines epinephrine (adrenaline) and norepinephrine. This test measures the amounts of metanephrine and normetanephrine that are released into the urine over a 24-hour period.

Catecholamines are produced by the adrenal glands (as hormones), small triangular organs located on top of each kidney, and by cells of the sympathetic nervous system (called neurotransmitter substances or neurotransmitters). The primary catecholamines are dopamine, epinephrine (adrenaline), and norepinephrine. Catecholamines are released in response to physical or emotional stress. They help transmit nerve impulses in the brain, increase glucose and fatty acid release for energy, dilate small air passages in the lungs called bronchioles, and dilate the pupils. Norepinephrine also constricts blood vessels, which increases blood pressure, and epinephrine increases heart rate and the rate at which the body uses energy (metabolism).

Normetanephrine is an important metabolite of norepinephrine and serves as a marker for the activity of the sympathetic nervous system. Measuring normetanephrine levels can provide valuable information for diagnosing and managing certain medical conditions associated with sympathetic nervous system dysfunction.

Norovirus affects people of all ages causing 19 to 21 million illnesses in the US per year. It is the leading contributor to acute gastroenteritis (AGE) across all age groups. While infections can occur year-round, Norovirus outbreaks tend to peak in cold weather. Norovirus infection symptoms include vomiting with watery, non-bloody diarrhea and abdominal cramps; occasionally fever, headache, muscle aches, or fatigue.

Norovirus GI & GII, or Norwalk virus, is the most common cause of non-bacterial gastroenteritis in the world. It is widely known for causing the stomach flu on cruise ships. Three genotypes of this diverse virus, GI, GII, and GIV, can infect humans.

NT-proBNP is a diagnostic screening tool to differentiate between people with normal and reduced left ventricular systolic function.

- N-terminal (NT)-pro hormone BNP (NT-proBNP) is a non-active prohormone that is released from the same molecule that produces BNP.

- B-type natriuretic peptide (BNP) is a hormone produced by your heart.

- Both BNP and NT-proBNP are released in response to changes in pressure inside the heart. These changes can be related to heart failure and other cardiac problems.

Levels goes up when heart failure develops or gets worse, and levels goes down when heart failure is stable. In most cases, BNP and NT-proBNP levels are higher in patients with heart failure than people who have normal heart function.

NT-proBNP (N-terminal pro B-type natriuretic peptide) is a protein released by the heart when it is under strain, often due to conditions like heart failure. Normally, only small amounts are found in the blood, but levels rise when the heart struggles to pump effectively, making NT-proBNP a valuable marker for diagnosing and monitoring heart failure. Doctors may order this test if you have symptoms such as shortness of breath, swelling in the legs, fatigue, or unexplained coughing. It can also help assess the severity of heart failure, guide treatment decisions, and track how well therapies are working.

NT-proBNP results vary with age and kidney function. In general, values below 300 pg/mL make heart failure unlikely, while higher levels suggest the heart may not be pumping properly (cutoffs are 450 pg/mL for people under 50, 900 pg/mL for ages 50–75, and 1,800 pg/mL for those over 75). Levels can also be influenced by obesity, kidney disease, and certain medications. Unlike BNP, NT-proBNP is more stable in the blood, making it a reliable test for evaluating heart function. If elevated, your doctor may order additional tests, such as an echocardiogram or ECG, to confirm the diagnosis and guide treatment.

The nuclear dot pattern is a fluorescence pattern seen on a positive antinuclear antibody (ANA) test by indirect fluorescent antibody (IFA) method. It appears as discrete bright dots within the nucleus of HEp-2 cells under a fluorescent microscope. The two main sub-types are multiple nuclear dots (AC-6 in ICAP nomenclature — classically around 6–20 dots per cell, generally related to PML nuclear body antigens) and few nuclear dots (AC-7 — classically 1–6 dots per cell, related to Cajal bodies). The multiple nuclear dots pattern is most strongly associated with primary biliary cholangitis (PBC) through antibodies including anti-Sp100 and anti-Sp140. The few nuclear dots pattern has substantially lower positive predictive value for any specific disease. Both are reported when the overall ANA by IFA is positive, and clinical significance depends on the specific sub-type, titer level, liver enzyme pattern, and associated specific antibody test results.

The nucleated cell count in CSF is a vital marker of immune system activity within the brain and spinal cord. Elevated levels often point to infection, inflammation, malignancy, or other CNS pathology, and always require interpretation in the context of other laboratory findings and clinical symptoms. A normal count generally suggests no active CNS inflammation or infection, but results must be considered alongside the patient’s overall clinical picture.

Nucleated Red Blood Cells (NRBCs) are immature red blood cells that have not yet expelled their nucleus. In a typical Complete Blood Count (CBC) test, the presence of NRBCs is significant and can provide valuable insights into a patient's health. While NRBCs are common in the bone marrow, where red blood cells are produced, they usually do not circulate in peripheral blood. Therefore, the appearance of NRBCs in a CBC test panel is noteworthy and often indicates an abnormality or a stress response within the body.

The percentage of NRBCs in blood can be crucial for diagnosing various conditions. Normally, these cells are filtered out of the bloodstream as they mature in the bone marrow, so their presence in a CBC indicates that the bone marrow is releasing cells into the bloodstream prematurely. This can occur due to several reasons, such as severe anemia, hypoxia, bone marrow disorders, or other conditions that disrupt normal red blood cell production. In such cases, the bone marrow may be overactive or under stress, leading to the premature release of these immature cells.

NRBCs (Nucleated Red Blood Cells) are immature red blood cells that still contain a nucleus. In healthy adults and children older than approximately one week, NRBCs are not present in circulating blood — they are confined to the bone marrow where red blood cells mature. A result of 0.0, or a notation like "< 0.20 × 10⁹/L [0.0–0.2]," is normal and expected. When NRBCs appear in peripheral blood above the upper limit of normal (typically above 0.02 × 10⁹/L or above 0/100 WBC), it signals that the bone marrow is releasing immature cells under stress — most commonly from severe anemia, severe hypoxia, or bone marrow pathology.